Comments and suggestions on this page are quite welcome. If you have a hint, or a useful trick, please send it in.

Superscripted numbers reference end-notes

Remember that there are many phases to building repeaters:

1. The decision that another repeater would be a good thing.
2. Acquiring parts.
3. Mounting all the parts in an open workshop rack.
4. Locating smaller parts since not everything fits.
5. Making the assembly of parts work as a unified whole.
6. Rebuilding parts or locating replacement parts since you don't discover that everything doesn't work together until you power it up.
7. Making the new collection of parts work as a unified whole.
8. Spending hours and hours programming and reprogrammin the controller to get it "just right".
9. Beating the final gremlins into submission, including the intermittent that only shows up at 4am on fifth Sundays during a full moon.
10. Finding a permanent home for the new repeater, and envying those that get their sites for free.
11. Taking the wife out to dinner a few times to make up for the evenings you spent in the workshop.
12. Preparing the site (backup battery bank (if needed), installing the antenna and the feedline on the tower, and more... (which may require borrowing a 4x4 vehicle)
13. Installing the repeater, item by item, into the permanent rack cabinet.
14. Making longer cables to replace the ones that no longer reach.
15. Making everything that broke work again.
16. Transporting the rack cabinet to the repeater site (which may require borrowing a 4x4 vehicle). And read that as eventually needing to buy a 4x4.
17. Fixing what broke during transport, including retuning the duplexer.
18. Spending several evenings and weekends beating the last gremlins into submission (which may require borrowing a 4x4 vehicle).
19. Taking the wife out to dinner a few times to make up for the evenings and weekends you spent at the repeater site.
20. Formal announcement that the repeater is on-line and available.
21. Locating and fixing the intermittent that only shows up at 4am on fifth Sundays during a full moon.
22. Listening to the users whine that they can't "get in" with their fleapowered HTs from 100 miles away.
23. Listening to the jammers.
24. Listening to the users whine about the jammers.
25. Listening to the other users whine about the users that whine about the jammers.
26. Taking the wife out to dinner a few times to make up for the evenings and weekends you spent at the repeater site.
27. After a few years deciding that the user-caused hassles aren't worth it, and selling the repeater to some other ham for about one-tenth of the money that you have into it, and realizing that the hundreds of hours you spent on it are worth zero.
28. Becoming a repeater user yourself for a few years.
29. Realizing that having another repeater would be a good thing.

Hardware

• The repeater itself. This might be a packaged repeater, or made of of a separate receiver and transmitter. The transmitter may be made up of a single unit or a separate low power transmitter, sometimes called an exciter (5 or 10 watts is common) followed by a separate power amplifier.
  • The repeater main channel receiver, on the proper frequency ^{1,3,5 and 12}
  • The repeater main channel transmitter, continuous duty rated, on the proper frequency ^{1,5,9 and 12}
• The duplexer ¹¹. This allows the recever and transmitter to share an antenna.
• Notch / Band-pass filter ¹²
• An isolator or circulator for the transmitter ⁹
• A DC Power Supply ²
• A battery bank and the associated charger (optional) ²
• Coax jumpers between RF components and the connectors (see ^6,7 and ⁸ under "Construction")
• Antenna(s), plus any necessary mounting hardware
• The feedline that connecte the antenna on the top of the tower to the equipment inside the building
• Lightning Arresters / Suppressors (Huber & Suhner, Polyphaser, etc) ³
• Grounding System / Equipment
• Rack or cabinet ⁴
• Control receiver and it's appropriate feed-line and antenna (optional)
• Link receiver(s) and transmitter(s) and appropriate feed-line(s) and antenna(s). (optional)
  In some cases duplexers on the link frequencies may be required.
• Support electronics (see below)

Hardware Notes:

1. In some areas the coordinators have "test pairs" - specific shared, non-protected (SNP) frequencies where new repeaters are built and tested. The idea is to minimize the "paper repeater" problem... repeaters that exist nowhere but on paper forms in the coordinators file cabinet. You build your system on an SNP frequency, and after it is fully built, on the air in your garage, and "kerchunkable" by the coordinator or his agent he knows that you are for real and serious. Then when you show a signed site agreement you are assigned a "real" frequency and you move your repeater to that frequency and put your repeater up at the site. However, it's a good idea to ask the coordinators in advance if there are any frequencies to be had in the geographic area that you intend to cover, and acquire the repeater radios that cover those frequencies. For example, the "waiting list" for two meter channels in some major metropolitan areas is measured in years, and in those areas you are much better off starting on 6m, 220 MHz, 440 MHz, 900 MHz or 1200 MHz and acquiring the repeater radios on that band. As to sites, and site agreements, you may find these two web pages interesting: Where is my repeater? and A Sample Set Of Radio Site Rules
   
   
2. You may choose to acquire a repeater power supply with a battery backup feature, or maybe yours came with that option. If you make use of that feature you will also need appropriately sized batteries, and an automatic charger (if the power supply does not have that built in, and frankly some of the internal chargers are not that good and frequently are disconnected in favor of something better and mounted externally). You will also need a Low Voltage Disconnect unit that will prevent harmful over-discharge of the batteries (depending on the battery chemistry you can kill a battery bank, or at least shorten its life tremendously, by discharging it below 30%-50%... yes, your 200 amp-hour battery may be damaged if discharged below 50%). Some flavors of lithium can be discharged down to 10% before damage but lithium has its own set of problams - like unable to charge at low temperatures.
   
   Some folks just build a complete 12-volt-based system, and power it from a common 12 volt AGM battery, and put a top quality automatic charger on the battery. If you can't find a battery back-up power supply, or if your system uses a tube type transmitter, consider using a UPS that'll ride through the time between the commercial power failure and the time the on‑site auto‑start generator kicks in, if your site is so equipped (and is maintained so it actually works... and I've seen too many sites that have old rusty abandoned generators).
   
   This UPS will also keep your repeater running. Note the manufacture date of the UPS internal batteries (or of the UPS itself) on a p-Touch label or post-it note on the top of the unit and plan on replacing them periodically (many corporate information technology departments automatically replace their server UPS batteries at 2, 2.5 or 3 years, the date varies with the company and the manufacturer of the UPS)... you don't want to discover that the UPS batteries are dead when the power fails and 15 seconds later the UPS croaks... been there, seen that and been bit badly by that... Some UPS units have a low‑voltage shutdown that kills the AC inverter when the internal battery voltage hits a certain discharge voltage (to protect the batteries from damaging over‑discharge), others don't and others are selectable... you want one that has the low‑battery‑voltage shutdown operational. Test your UPS on low voltage AC, what will it do if the AC line voltage drops to about 70-75 volts? If the power company loses a phase on the line that goes up the hill that's what your AC voltage will be... Been there, got bit by that. More on this topic later in this writeup.
   
   Another reason to be careful on which UPS you get, as depending on the design they can create RF hash, and others can have as much as a 150‑200 millisecond outage as they switch from AC to inverter/battery. Tripp‑Lite brand units do not have the outage, many APC brand units do. Don't assume, test! Just plug a 100 watt incandescent lamp into the UPS and pull the plug! Does the lamp blink off momentarily? It does on my APC "BackUPS Pro 1000". Fortunately all of my home computers, the DSL modem, the router and the ethernet switch have enough filter cap energy storage that they "ride out" that momentary blink.
   
   Another UPS "gotcha" is that some models are not frequency tolerant. Let's say that the power to the site fails, the UPS kicks in, and the on-site genny cranks up and starts to run. It comes up to speed and the governor is a bit out of adjustment and it settles down at 63 Hz. We have beautiful power, it's just a bit off frequency. The average linear or switching power supply won't care, but your UPS may "see" that slightly off frequency sine wave as bad power and not switch back from battery to power line (and I'm not picking on 63 as a threshold number); the UPS should charge the battery with whatever comes in, and the inverter makes 60 Hz going out.
   
   Pay extra attention to the charger and the Low Voltage Dropout unit. Use a top‑quality, automatic charger, and make sure it is fail‑safe. You don't need a failed charger boiling and cooking your expensive battery bank. A good reference is Home Power Magazine. HPM is the bible of the off-the-power-grid community, and the web site has a wealth of information. Plus, they walk the walk as well as talk the talk - the entire magazine is produced with home-made electrical power, and it's edited and published by a ham. They periodically package all the back issues for several years on a CD (one PDF file per issue). More information is on their web site.
   Update: Home Power Magazine is no more, is was published from October 1987 to November 2018. But the entire run is browsable and downloadable and there is a LOT of good information there.
   
   Watch out for the occasional device that needs a weird supply voltage - for example the GE Voting panel uses either 120v AC or 28v DC, and some higher power transmitters (the 100 watt MTR2000 is one) uses 24 or 28 volts DC. GE has a 12v DC-to-28v DC inverter option for their voting panel, Motorola hasn't had any DC-to-DC converters in their catalog since the transition days from 6 volt to 12 volt vehicles back in the 1950s. The end result is that you may end up running the battery bank as 24 volts or 28 volts and using a 24 volt-to-12 volt converter to power the rest of the rack, or even running two separate strings of batteries with a common negative, one on 24 volts and one on 12 volts, each with its own charger.
   
   DO NOT run a single series string battery bank with a mid-voltage tap as the cells above the tap will be overcharged and the ones below the tap will be undercharged. Both situations will kill the battery bank quickly.
   
   As a final test before you take your system to a hilltop site take your rack and plug it onto a LARGE variable transformer (Variac™ is one brand) that can handle the full load of the entire rack (with every transmitter keyed). If you have a problem locating one, talk to a local stage theater group - they frequently use them as dimmers for incandescent lamps, and some of the lamps run 300w, 500w or even 1000w. Set the Variac for normal voltage (i.e. 120v AC) and plug your rack into it, switch the system on, and in a mode that keys all the transmitters simultaneously. Quickly twist the mains AC voltage down from 120v AC to about 70-75 volts AC and see what happens. What's so magical about 70-75 v? The AC power distribution system in the USA uses what is called three-phase power. If there is a power problem that results in a dropped phase, or an outage on one phase, the 120vAC voltage will drop to between 70 to 77 volts, the exact voltage will depend on loss in the copper line to the hilltop and the load on it.
   
   Why am I mentioning this? Several years ago I heard about a mountaintop system at a site that lost a phase due to a bad splice on the power line up to the site. The controller went into a funny mode that keyed the main repeater transmitter, the autopatch downlink transmitter (the phone line was at the owners house and linked in), and the remote base transmitter. And keyed them for hours. And hours. And hours. The system would not respond to Touch-tones on either the main channel or the control channel. It took a hill trip to shut the system down. Switching the power off and back on (with full line voltage) brought everything back to normal. In this particular system the repeater and link radios continued to operate as they were fed by a switching supply that operated just fine at the low voltage, but the controller had its own linear supply that didn't... Testing with a borrowed Variac™ showed that if the AC mains power dropped below a certain threshold voltage the control system microprocessor went crazy, keyed the transmitters, and halted. With the CPU halted it ignored all DTMF commands. Bringing the voltage back up did not reset / restart the processor - it took a power outage and restoral to full voltage (i.e. switching it off and back on). Most people remember to design for power outages, but very few remember to test for proper behavior under low voltage conditions, and technically a "brownout" is above 95v AC). The solution on this particular system was a "belt and suspenders" fix - they added a power monitor chip (Dallas Semi and Maxim both make them) to the controller CPU that would provide an orderly shutdown of the controller on low DC voltage (i.e. prevent keying the transmitter(s)), and they replaced the controller power supply with a switcher that made clean DC power down to 50v AC.
   
   
3. If you plan on putting your system at a high RF level or commercial 2-way site, you should look at the antenna system at the site. Some sites use a shared receive antenna with a bandpass filter then a distribution amplifier. This is the case at three of my sites: a 10db stick at the top of the tower, feeding a high level preamplifier, then a 4-port multicoupler / splitter, with each port feeding an 8-cavity "window" filter (one for 440 ham, one for the 450 commercial repeaters, a third for the 460 repeaters, and a fourth for the 470 repeaters. Each filter output feeds a distribution amplifier which feeds a multicoupler / splitter that feeds all of the receivers in that band segment. More on this later.
   
   If you are at a busy site and don't have a window filter or some sort of a bandpass cavity in front of your repeater receiver then you will probably have issues.
   The front end of a low-end repeater or a mobile radio is not appropriate for a high level RF site as a primary receiver. It has very little rejection of off-frequency strong signals that will cause receiver desensitization or blocking.
   
   Another caution note for commercial sites: you may be limited as to the type of rack or cabinet or battery backup system you can use. Some sites have a 12 volt "site battery bank" you can tap into, others will let you put a Rubbermaid or similar car battery box next to your rack, others may require the battery IN your rack which leaves your only option as a rack shelf full of gel cells (trust me - don't put a wet battery inside your rack... you really don't want acid fumes inside your cabinet)... So plan ahead and get a copy of the site requirements in advance and build your system around them. You may find this web page relevant: A Sample Set Of Radio Site Rules.
   
   
4. Do a cooling plan: some equipment runs hot and needs fans, other can be cooled by convection and only needs open air flow. A non-contact thermometer (like this one at $50) can be useful to read surface and heat sink temperatures. Some cabinets will need fans to aid natural airflow around heat-generating parts. If so, consider TWO fans in the cabinet. If one fails, the other will remove the heat. Put finger guards on both sides - those blades are very unforgiving. Maybe even have double fans with the second set on a thermostat (i.e. idle until needed), with the thermostat also triggering an alarm pin on the controller so you know that the primary fans have failed. If you chose to use two full time fans make sure that they are from different manufacturers and different vintages - you don't need two identical fans bought at the same time, and used for the same amount of time, as they will fail at about the same time (and Murphy's Law says that the failure will happen during the city festival / marathon race / some other public service event where the failure is just too, too visible...). Use good quality fans: the cheapest ones use plastic bushings, the mid-grade ones use bronze bearings or bushings, the good ones use ball bearings, and the best use needle bearings (which are rare, mil-spec, and priced accordingly; the ball bearing fans are quite appropriate). Don't install used or surplus fans (unless they are New Old Stock) as you have no idea how much life they have left (and there are surplus places that will pop the bearing caps and add some auto axle grease to quiet them down and give the impression they are NOS). One trick: if you don't need a lot of airflow, get two fans and wire them in series, or use a single 220vAC fan on 120vAC... you still have air movement, the fan lasts longer, and a lot less noise... and if you do the two-in-series trick you can have a DPDT relay controlled by a in-rack thermostat to switch them from in series (quiet but low air flow) to in parallel (loud but high air flow).
   
   Think twice about using DC fans unless you are on a DC only system.... many will put grunge back up the DC power line. Been there, seen that on a GR-300 intermittent-duty repeater. The DC fan made enough grunge on the +12vDC line that it modulated the transmitter. If you use DC fans, assume that they will, and put a 25-50mfd cap across the fan terminals, a 470pf or 1000pf in parallel with that, and a DC choke in series with the power to the fan. If you use two fans put that noise network on each one, and right up against the fan terminals. Why the two caps? Most electrolytics are great at low frequencies (under 25 kHz) but are an open circuit for RF. The 470pf or 1000pf cap handles the RF. And the short leads gets it right up against the fan to minimize the "receiving antenna" length.
   
   A final note on fans: before you mount them, test them as to RF generation. Some of the solid-state commutators used in modern fans (especially the variable speed ones) are RF hash generators, and some are grunge generators when placed in an RF field (i.e. they need external excitation). I've seen a fan that was dead quiet (RF-wise) until it was in an RF field, then the external RF excitation created trash on the system 440 input frequency. The simplest way to test a fan is to use a dual band handheld and a spectrum analyzer. Set the analyzer for a wide spectrum (i.e. 1‑500 MHz) and key the handheld - you should see one spike. Put the fan (powered up of course) next to the analyzer antenna and see if it's a grunge generator. Then key the handheld with its antenna right next to the hub (and don't forget to test with both VHF and UHF on the handheld). If it's still one spike, then you have a good fan. If it looks like a comb or a blob (and cleans up when the handheld is unkeyed or when power is removed from the fan), you've got a piece of junk best used in the back of the TV set or to suck the soldering iron fumes away from the workbench...
   
   Consider vibration from the fans. Add lockwashers (split or star format) under EVERY nut that is in a piece of RF equipment. Not only will they prevent things from becoming unscrewed, but they will prevent grounding cracklies. A friend had the coax connector on the back of the transmitter power amplifier come loose - it took several years of fan vibration to cause the problem, but when it did it caused all kinds of intermittent desense and was somewhat dependent on temperature. And it was hard to find. Finally someone bumped the cable... all sorts of cracklies happened and the desense would go through the roof or totally disappear.
   
   
5. Another construction note: Have the cabinet power cord terminate in a 4 or 6 outlet power box / power strip and continue to a second switch / power strip, then continue to a third switch / power strip. The first set of outlets you consider as "unswitched" and can be used for things like rack lights, test equipment and soldering irons, the seconds set of outlets are for all non-transmitting equipment, and the last set for transmitters. The last switch kills only the transmitters, the second-last switch kills the entire repeater. Use heavy duty / oversize power cords on the system - two amps from this item, three amps for that item, two more from a third item, five amps to the system power supply, and all of a sudden that #18 extension cord is getting rather warm (#18 is UL rated at only three amps), where #12 will handle fifteen amps, and #10 will handle thirty amps).
   And to preclude on-site "accidents", you probably want to use a twist-lock plug on the end of the cord. After the second visit to one site to simply plug our rack back into the wall outlet we converted the outlet and changed our plug to a twist lock and the problem went away.
   On the other hand, if the building has overhead outlets then twist-locks are quite appropriate for those. The drop cord from the overhead outlet can terminate inside the rack.
   
   
6. Unless your site agreement precludes it, bolt the rack cabinet to the floor of the site. Some sites require that for earthquake reasons, but you will want to do it to preclude theft. Yes, people have had their repeater die, go to the site the next day, and the entire cabinet is completely MISSING. Been there, had that happen to a friend's rack / system around 2001 and not one piece of the system has ever showed up even with every serial number entered into NCIC. You will want to have someone take some pictures of both sides of the rack (with the doors open) installed on site including one with you holding today's newspaper above or next to the rack as proof that it did exist at that location on that date. Take a full set of photos showing every piece of equipment and put them in the scrapbook - it may be the only evidence you have to give the insurance man.... If your group includes a Notary as a member, or as a members spouse or child have him / her certify that the photos were taken on that day at that location (many real estate offices and legal offices have a notary on staff).
   
   
7. You will find that almost all high-traffic repeaters are ex-commercial stations (i.e. a GE MASTR II, a Motorola MICOR, or similar). If you use one consider adding the local test / diagnostic metering panel that is made specifically for the radio (if it didn't come with it). They show up on eBay on a regular basis. Or build or modify one - the MSR2000 test set is not as common as a MICOR, and you can swap two wires in a MICOR set and use it on an MSR... If you have an analog test point on your controller consider using it to measure the DC voltage from the squelch noise in your receiver. Then keep a set of baseline measurements of the voltage from several of your user's base stations in the log, especially those that aren't quite full quieting. Knowing, for example, that when George has his base station in the low power position he gets in at 80% quieting and 2.1 volts and all of a sudden he's at 1.5 volts says that maybe the repeater receiver (or his transmitter) needs looking at... (even if George runs at high power normally). And a relay tree can multiplex a single analog test point to multiple points in the receiver and the transmitter. In other words, having remote diagnostics can be, to use a Martha Stewart term, "A Good Thing".
   
   
8. If you are using programmable radio(s) in the system you might want to have a floppy disk or flash drive with the RSS and code plugs for the radio equipment that's installed there. An extra RIB with all the cables you'd need to connect it to a laptop and your radios is nice. Don't forget the wall-wart power pack to run the RIB (don't leave batteries in the RIB to die and corrode).
   
   
9. Every transmitter needs a ferrite isolator followed by a pass cavity or a low pass filter between the output connector and the antenna system. A circulator is a 3-port device that presents a consistent 50 ohm load to the transmitter, no matter how bad the antenna is messed up. The third port has a dummy load cabled to it. A isolator is an circulator with a built-in dummy load. Either needs to be followed by a pass cavity as they will generate harmonics. Together they make up an assembly called an intermod panel, and that is usually a contract requirement at large commercial sites (see A Sample Set Of Radio Site Rules). I use a Z-Matcher on the output of every PA deck because the duplexer expects a 50 ohm source, and in many cases the PA deck isn't (especially if run out of its designed frequency range - like a 150-160 MHz transmitter run at 145 MHz, or a 450-470 MHz run at 442 MHz). Even if the Z-Matcher and isolator / circulator is not required at your particular site, it's worth every penny to save those fragile (and difficult to repair) transmitter PA decks.... have you priced out a 100 watt 2 meter or UHF MASTR II continuous duty station power amplifier recently?
   
   
10. DO NOT assume that you can use a mobile radio as a repeater transmitter in anything approaching a continuous duty environment unless you have verified that it was designed to work in continuous duty mode. They can be used quite readily as a low-to-medium performance repeater receiver, or as a link receiver, or an an exciter, but you cannot use it as a repeater transmitter or link transmitter without due consideration to the normal mobile radio limitations on RF power and duty cycle. Mobiles have a undersized heat sink (to minimize the package size) and hence are limited to a 10% to 15% transmit cycle (read the book that comes with them if you don't believe me), which translates to 10 to 15 seconds out of every 100 seconds and the radio will burn itself up if run at full power in regular high-duty-cycle repeater service. On the other hand, there are some mobiles (like the GM300) that will work quite nicely as an exciter for a external continuous duty amplifier.
    
    Remember that a repeater is a device that allows one-to-many communications rather than a cell phone which is a one-to-one. As such, while any individual user may only transmit for 10 to 30 or even 60 seconds the repeater is transmitting for the entire conversation of all the users (how long does a roll call net last?). Duty cycle is the ratio of transmit time to clock time. A 15% duty cycle radio is designed to transmit at full power for no more than 15 seconds out of each 100 seconds. This is not to say that you can't transmit for three minutes, but the transmitter is going to get very hot. Most mobile radios have power control circuitry that turns the transmitter power down if you talk too much, but do you want a situation where your repeater transmitter goes into shutdown on its own, in the middle of a conversation? This WILL happen after some period of continuous transmitting, even with tons of cooling air and a low power setting - been there, seen that. You really don't want your repeater fading out during something important like a 911 autopatch call or a disaster net.
    
    In short, with very, very few exceptions, a mobile radio used at full power as a link or repeater transmitter is a recipe for failure, especially if the system is a linked system with high duty cycle... as I said above, the repeater is transmitting for the entire conversation of all the users, with a linked system the user pool now includes everybody on the local system plus everybody on the far end node, or if connected to an IRLP or EchoLink reflector then everybody on every node.
    
    
11. Saying "duplexer" is like saying "car". They come in various types, makes, models, and performance levels. Some are notch-only, others are notch-pass. There are 2-cavity, 4-cavity, 6-cavity and the author saw one that was 8 cavities (which gives a higher level of isolation, but at a cost of insertion loss). There are ones that have two cans on one side and three on the other. There are ones that are designed to combine two transmitters into one antenna. There are 1/2 dB loops, 1 dB loops and adjustable ones that go up to 3 dB loops. There are notch-only duplexers that are helpless against any other transmitter within earshot - they pass everything to the receiver except the one transmitter they are connected to. The author saw a custom 7 cavity one ... it was a 6 cavity unit on a 147 MHz 2 meter repeater and the extra cavity was cabled into the duplexer and allowed a 144.39 MHz APRS station to share the antenna.
    
    Be suspicious on any inexpensive used duplexers - I have seen used ones that have arced over internally and look perfect - but before they will ever work will need replacement glass piston capacitors that are over $100 each. And then you get to swap them, which on some designs is easy and on others will require soldering skills with a tiny propane torch. Do your research before laying down your money to buy any second hand duplexer.
    
    And you may not need a duplexer. The author has several UHF amateur repeaters at commercial sites that have UHF master receive systems and combined transmitter systems. This is covered in the next paragraph. And you may not need a duplexer if you use split sites. Locally we have a 10 meter repeater with the receiver at one ham's house and the transmitter at another that is a half mile away... with a ¹⁄₂ watt 420 MHz point-to-point UHF link with small beam antennas. Until the operator lost one of the sites there was a 6 meter repeater with a receiver on one site and the transmitter at another, also with a 420 MHz point-to-point UHF link. A good system can be built with no duplexer at all.
    
    
12. Some of the better commercial sites have a master receive antenna system (almost always on UHF), sometimes called a community receive antenna system. This is a system where the building has a top-quality antenna at the top of the tower feeding top quality low-loss feedline which runs into the building where it feeds a high level preamplifier and bank of bandpass filters (also known as window filters). Each filter feeds a distribution amplifier system that connects to all of the repeater receivers in that band segment. TV channels 14-20 are subject to local allocation, and some are TV and others are commercial or public safety repeaters (with a +3 MHz offset). The author takes care of multiple sites, and several have have this system. At a typical site the UHF receve antenna is a very broadband design that covers 406-512 MHz, and feeds multiple 6 or 8-cavity bandpass filters, one for each band marked with a *:
    • (The 406-420 MHz range is government and military systems and they generally have their own sites / buildings)
    • * 420-436 MHz (low UHF amateur radio, mostly control links, ATV and point-to-point links)
    • * 436-445 MHz receive (high UHF amateur radio - southern California UHF repeaters receive from 440 to 445 MHz)
    • * 455-460 MHz receive (commercial repeaters that transmit from 450-453 MHz)
    • * 465-470 MHz receive (commercial repeaters that transmit from 460-463 MHz)
    • (TV channel 14 - 470-476 MHz is commercial 2-way in southern California)
      * 473-476 MHz receive (commercial repeaters that transmit from 470-473 MHz)
    • (485-488 MHz receive - TV channel 16 - 482-488 MHz - is public safety in southern California and they generally have their own sites / buildings)
    • 494-500 is TV channel 18 with an active station in southern California.
    • * 509-512 MHz receive - TV channel 20 - 506-512 MHz is commercial 2-way in southern California)
    Each of the 6 filter outputs feeds a distribution amplifier, and that output feeds a multicoupler / splitter, with one port for each repeater receiver. Needless to say, this type of system is expensive.
    
    Master receive antenna systems are ususlly paired with separate transmit antennas, or combined transmit antennas. Note that if you have a master receive antenna and either a separate transmit antenna or a shared transmit antenna (a combiner) then no duplexer is needed. The combiner includes the isolator or circulator mentioned in ⁹. At several sites that the page maintainer visits there are five 100 watt transmitters feeding a five-port combiner, and the combiner feeds a single transmit antenna (which needs to be a 500 watt version). The fedline on a combined antenna is typically 7/8 inch or larger Heliax™.
    
    

Electronics

• Repeat audio output from each receiver, filtered to remove CTCSS / DCS, and wired to be independent of the local speaker volume control.
  
  
• COS circuitry for each receiver (generates a logic signal that tells the repeater controller when a signal is on the input frequency). Note that the COS follows the carrier, not the audio mute line, which may be affected by the CTCSS / DCS decoder.
  
  
• CTCSS / DCS detector circuitry for each receiver (generates a logic signal that tells the repeater controller when the receiver is hearing the correct PL tone or digital PL code), independently of the COS. Many receivers have this built in. Some systems have additional decoders for multiple tones.
  
  
• A local speaker on each receiver, controllable by the local volume control (and your system should be built so that changing the local volume control level does NOT change any repeater audio levels - those should be clearly labeled screwdriver adjusts). Design your system so that twisting ANY visible knob does not change the on-the-air repeater parameters. Set up all switches so that in the down or left position they are "normal". Use green LEDs for power, and red for problems or PTT. There will be times when you are at the site, have finished a long day, are exhausted, and want to just pack up and leave. If the system switches are set up so that green is good and down is normal all it takes is a quick look before you close the cabinet door.
  
  
• Include a local microphone on each transmitter, wired to mix into the repeat audio. Radios like the MICOR or MASTR II station have a transmit audio mixer function built in. Have a "takeover" switch on each transmitter that can kill the PTT and repeat audio from the controller port. Picking up the local mike and talking should mix the local mike with the repeat audio on a 1:1 basis. Actuating the "takeover" switch should leave the local mike as the only transmitter control. If you have multiple transmitters you can either have multiple microphones or just one and a rotary switch to select which transmitter it will be connected to.
  
  Most newer repeaters have a separate microphone connector and an anxilary transmit audio input (frequently on the accessory comnnector) which also has a pin for External PTT (EPTT). A simple DPST OR DPDT switch can be wired to interrupt the repeater controller connection, with one pole enabling controller audio and the other pole enabling EPTT. When the switch is off then the only connection is the micophone jack.
  
  
• Repeater controller ¹, containing:
  • IDer for each transmitter
  • DTMF decoder for each receiver and function latches
  • Audio mixer for each transmitter and audio muting for each receiver or signal source
  • Carrier delay timer (also called the hang-in timer or squelch timer)
  • Transmitter timeout timer
  • Digital inputs and digital outputs for sensing and switching other items in the rack
  • Autopatch (while many groups have dropped the patch due to cost, realize that if you will be a hero if you bring a working dial tone to a disaster where all the cellphones are out...). If you can get a free phone line through the local Emergency Management / Disaster Communications office do so, and include the autopatch option in your controller.   Remember that the Public Safety groups (i.e. police, fire, etc), hospitals and emergency management groups are at the top of the priority list for telephone service restoration after a disaster.   If you do get an EM sponsored wireline telephone line it will be at the top as well, so make sure that your system can survive a power outage or other similar avoidable problem.   Just realize that EM-sponsored phone lines are paid for by EM money and you may not be able to make personal calls on it.
  • If you end up with a controller that has a voice recorder (sometimes called a DVR) then you can have recorded announcements.   If you do so, do not use a club member, a control op or the owner doing the announcements - use a non-ham with a good clear speaking voice (and one that you won't get tired of after hearing 10 times a day).   The audio path of most DVRs is so clean that if you use a local recognizable voice (like the system owner) you will have users assuming that the announcement is the owner doing it live on the repeater input.   Someone will call the voice on the DVR track by call-sign, and get annoyed when they are ignored, then feel very stupid when they realize that they've put their foot in it in public - and they will be angry at the owner of the voice on the track, not themselves.   Been there, seen that happen, watched the owner try and mollify the club treasurer (who was too proud to accept an apology for his own actions).
    
    
• Support equipment - like a monitor amp that you can switch to any receiver output, or any transmitter input (see the note under "Construction" below). Maybe a fan controller to keep that transmitter power amplifier cool. You don't want to run the fans 7x24 as that's wasted power (and fan life) if nobody keys it up for 8 hours (or more), yet you don't want to repeatedly cycle the fans by running them based on PTT only.
  
  

Electronics Notes:

1. Many systems "outgrow" their controllers... they start out as a simple repeater (perhaps on 2m) with a control receiver on a different band (perhaps 440), and eventually the owner and control operators add a transmitter to the control receiver side and make it into a complete repeater (on the 440 band). This repeater with a controller that started out as a 1.5 port (one repeater plus one control receiver) controller has just become one that requires a full 2-port controller. Then someone wants to add a NOAA weather receiver, or a remote base. However, most controllers are not expandable... so always plan ahead on the controller, and have at least one full port extra over and above your long-term plans. Or you can do like most and start out small and expect to replace the controller at a future date... The small controller can then go on the test bed repeater in your garage, or if your system has become an important community resource you may chose to put a backup repeater at a second site and the small controller can go there.
   
   Note that there are controllers with "full duplex" audio circuitry design and ones that are not. Controllers that use a single audio bus have limitations to deal with the case when a signal is being received from the repeater receiver and a different signal is being received from the link receiver at the same time. That is because you want the repeater transmitter to get a mix of both audio sources, while the link transmitter should get audio only from the repeater receiver. Under certain conditions the systems that have backbone linking disconnect the repeater transmitter from the links and they pass the audio from the link receiver just to link transmitter. With a single audio bus, that isn't possible. Most simple systems don't run into that limitation, but you want to plan ahead to allow system expansion. And remote bases introduce another (but similar) can of worms. In some situations where you have two or three point to point links plus a repeater (and maybe a remote base) all at one site you end up needing a crosspoint audio matrix from the receivers to the transmitters.

Construction

1. The Motorola MICOR stations, and probably others, have the receive audio coupled to the top of the local volume control with a jumper (look at the J2‑6 to J2‑14 jumper in the MICOR station conversion articles). That jumper can be replaced with a switch wired to allow selecting the receive audio or the audio going to the transmitter (so you can monitor the repeater controller output), and additional switch positions allow for more sources to be monitored. This trick turns the audio section of the main channel receiver into a free monitor / test audio amplifier.
   Note from WA6ILQ: We built ours with three or four position switches and you'd think they'd usually be on the receive audio but interestingly enough they spend most of the time monitoring to the main channel transmitter audio.
   
   
2. Plan for deconstruction - as you build the system, assume that you will have to remove parts. Don't "layer" the hardware - where in order to remove item 1 you have to remove item 2, and in order to remove item 2 you have to remove item 3.
   
   
3. Leave the clip leads on the home workbench - make yourself a rule that if it goes in the hilltop cabinet it is a finished circuit with real connectors and real cabling. Alternatively, have a rule that if there are "N" number of clip leads in the toolkit that goes to the site that "N" come home from the site.
   
   
4. Put individual DC power connectors on the equipment, and make them all the same (or at least minimize the types): Anderson Power Pole (preferred) or Molex or equivalent (if you have to) connectors. And use the real Andersons not the Chinese clones that have weak spring tension. Having disconnects in the proper locations lets you disconnect any single piece of equipment without having to loosen the nuts on the power supply and pull the lugs off. Murphy's Law says that the lug needing to be removed will be the one furthest away from the nut. Power busses are available, look for a "neutral" and "ground" buss at the local electrical supply. Another option is two‑contact trailer power connectors with a decent wire size, plus they plug directly into MaxTracs, Spectras, Radiuses and similar radios. Some groups make up a DC power panel with a separate DC breakers for each load, or splice several power connectors together with fuses in series with each one, and one set of lugs for the power supply. This will reduce the number of lugs connected to the supply. And notice that there are important internal differences between AC breakers and DC breakers, and you DO NOT want to use an AC one on a DC circuit or vice versa. One possible source of DC breakers is the repair shop(s) at the local small airport. Many have old fuselages out back that they cannibalize parts from, and sometimes will sell the used breakers (aircraft electronics are FAA mandated to a very high quality level and the circuit breakers rarely go bad). Don't be surprised or offended if they won't sell them or ask you to sign a release of liability or a guarantee that they won't go back into aviation service, the seller is just covering his legal posterior.
   
   
5. Silver plated RF connectors ONLY - no nickel anywhere, especially on 50 MHz and up. Ferrous metals (and nickel is ferrous) in an RF field do strange things. Preferred brands are Kings and Amphenol.
   
   
6. Use as few RF adapters as possible. Each one adds just a little bit of loss, but after a while, this adds up to something significant. If you have to use one make sure that it is marked in your mind as temporary - not permanent. If your duplexer to feed-line jumper cable needs a right angle connector on the duplexer end, buy a right angle connector and use it, not a normal/straight one and an adapter. And the point made in the previous bullet about silver plated RF connectors applies to RF adapters as well. I've seen a 900 MHz repeater that was working just fine go bonkers when a nickel-plated right angle "N" adapter was put in line (and that was the only change). That adapter worked just fine at 2m, but it generated gobs of intermod at 900 MHz. As soon as it was removed, the system went right back to normal.
   
   
7. Use good quality double shielded coax inside the cabinet. RG‑214, RG‑142 or RG‑393 or RG‑400 depending on the availability of the coax and on the connector size. Don't bother making each run as short as possible - if your equipment is truly 50 ohms and you use top quality cable then an extra few inches here or there (or even a foot) does not matter (except in duplexer or multi‑bay antenna harnesses). Make each run a reasonable length, including enough slack for servicing. RG-142 is good stuff, but it has a drawback: you can't flex it. This web page maybe of interest: RG‑142 versus RG‑400. Do not bundle receiver and transmitter coax together unless both are 100% shield (i.e. superflex). For audio cables the small diameter RG‑174 coax is excellent (as long as it's the mil-spec stuff, and not the cheap Radio Shack grade). I wouldn't use RG174 at RF frequencies as it's 9 dB loss per 100 feet at VHF (that's about 90% of your power), and almost 20 dB at UHF (close enough to 98% that it doesn't matter), but at audio frequencies it's great stuff.
   
   
8. It's common practice to locate the lightning arresters / suppressors in the outside wall of the building rather than in the top of your cabinet... much better to keep the lightning OUTSIDE the building. However the common Polyphaser arrester is not rainproof/waterproof/snowproof/iceproof. If you mount yours outside make sure that the ones you install are. Another good brand, in fact the one that is used at most cellphone sites and offers waterproof models, is "Huber & Suhner", also known as "H&S". I've seen one site that had an H&S in the outside wall and a Polyphaser in the top of the cabinet (and a Polyphaser phone line protector AND a gas tube arrester in series with each other on the wall behind the rack).
   
   
9. Lightning protection for the AC power lines is best done at the building level, but there are a few things you can do... First use a top quality power strip. The common "surge protector" strips uses a pair of Varistors inside, and the common failure mode of those are that they deteriorate into open circuits after time, which is worse than no protection at all. Two, is to make sure your rack is grounded to the building ground, so that if there is a strike the rack stays at the same potential as everything else. Read the US Military document on site grounding available at this web site on the Antenna System page.
   I've seen what a strike can do, at one employer we had a lightning strike in the transformer farm of the electrical substation across the street. All of a sudden the ground on that side of the street was about 500 kilovolts at 200 kiloamps above the ground on our side of the street... that does nasty things to phone lines, data lines and power lines. On our side of the street we had damage between the two buildings... the voltage hopped from the elevated voltage earth at one building over the ground protection onto the copper phone lines betweem the two buildings then over the protection at the other end and back to "normal potential" earth, and incidentally destroying the equipment hung onto both ends of the copper line.
   The third thing you can do is make it someone else's pocket that takes the hit: take lots of photos of your rack(s), feed-line(s) and antenna(s), and get ARRL equipment insurance on the entire system (i.e. everything at the site, including the antenna(s), feed-line(s) and Polyphaser(s). The fourth thing is a variant on the third: for a long time Tripplite Corp. offered (maybe still does) a $25,000 insurance policy on anything that was plugged into their "Isobar" line of surge protector outlets (which come in 4-port, 6-port, 8-port on-the-floor models, and a 12-port rack mount unit). I know of several system racks where the main AC cord terminates in an Isobar (those outlets are treated as the unswitched outlets mentioned above), and one outlet of the Isobar feeds the receiver power strip and one outlet of that one feeds the transmitter power strip.   The empty Isobar cardboard box with the insurance flyer inside sits on the owner's garage shelf. Other manufacturers have had similar types of deals (maybe still do). A while back I found one of those Isobars with the $25,000 sticker on it hooked to a friends home computer... the box was on the shelf, with the paperwork inside. I traded him a new hard drive for it. That Isobar is now on a club repeater.
   
   
10. If your repeater is going to have a phone line attached, don't forget lightning protection for that. The common aftermarket phone line "surge protector" use a pair of Varistors inside, and the failure mode of a Varistor is that they deteriorate into an open circuit. Gas tube arrestors don't do that - they either work or they are physically visibly broken. And it doesn't hurt to have one set of gas tubes at the telco protector on the building outside wall (with the ground point hooked to the outside telco ground), a second set on the inside wall where the phone line comes through the wall, with a separate ground wire going to the telco ground rod, and maybe a third set behind your rack with the ground wire strapped to the building perimeter ground (repeating the same rule - keep the voltage outside the rack). The gas tube units are open circuits until the trip voltage is reached, then they are a dead short. If you do get a strike, replace all three even if they look like they aren't damaged.
    Another trick that works (especially if you are constructing a brand new building) is to try the lumped impedance bump: run the phone line(s) underground for the last couple of hundred feet to the building and bury a 50+ turn coil of phone line about six feet from the building (naturally you would use a grade of cable intended for direct burial) and bury the coil at least two feet down in the ground. I saw this done at one site and the guys just wrapped an empty bleach bottle with two layers of phone line (the bleach bottle was first filled with packed dirt so it wouldn't collapse as the hole was filled in or if someone drove over the location). A few years later the site had a strike on the phone line about a quarter-mile to a half-mile from the site, and the energy was dissipated underground because the impedance bump in the phone line caused by the inductance of the bleach bottle coil (as small as it was) impeded the flow of energy. Both the coil of wire and the bleach bottle were vaporized, the telephone line protection (both the carbon pile and the gas tube protectors) on the outside of the building were blown away, the ones on the inside of the wall were only half gone (the gas tube was gone, one side of the carbon was gone), the ones on the wall behind the rack looked OK but were replaced anyway and the repeater equipment survived with no damage.
    
    
11. Use one‑foot lengths of #14 or #12 insulated house wire as in‑progress wire ties during construction so that as you build the custom length cables they are the right length to lie in place neatly when you are done. You can untwist and re-twist the copper wire ties as often as you need to during construction. Replace the copper wire ties with plenty of nylon wire ties AFTER the repeater is built and in its final rack or cabinet to make the wire bundles look neat (or just use Velcro strips from the beginning). Leave some cable slack for future servicing. Try to keep the DC and signal wires separate from the RF and AC wires. Some system builders have a rule: RF and AC power on one side of the rack, DC, audio and logic signal wires on the other. And have a bunch of nylon or Velcro wire ties in the in-cabinet toolbox and more in the take-to-the-site-and-back toolbox.
    
    
12. If the site has a backup generator don't use a ferro-resonant power supply. Ferro-resonants are excellent units, but they do have two drawbacks: the first is if the AC generator drifts off frequency (i.e. if the governor fails) you don't need the resonance capacitor blowing up like a bomb (yes, they do, and it's not pretty). Somewhere I have a photo of a cabinet door that has a dent pushing outwards from a detonated cap inside.
    The second point is that ferro-resonants have a high idle current, which can be as high as 2.5 amps at 120vAC with no load. If you are paying the power bill that can add up to a significant number at the end of the year. Figure 52 weeks a year x 7 days a week x 24 hours in a day x (amps) x (volts) x (your local kwh amount / 1000)... And the local kwh amount in the USA can be as low as 4 cents to as high as 45 cents.
    Note from WA6ILQ: Ferro-resonants may not be marked as such. The GE MASTR II base station supply is based on one. The "constant voltage transformers" or "power conditioners" that level out power line glitches do so with a ferro-resonant transformer inside the housing.
    
    
13. Document, document, document everything! Have manuals on everything. And make up a duplicate set that is kept at some other location. Try to write your reference materials for someone who may know very little about repeater systems. Don't think you will always remember everything you need to know - you will forget. Document it, no matter how trivial the detail may seem. If you make modifications to any equipment don't mark up the original manual schematics - make full-size copies of the appropriate prints and mark up the copies, then leave the copies along with the manuals in the system documentation binder. Put a Scotch "Post-It" on the original in the area of the modification with a note on it to refer to the marked-up copy. This is in case you later on remove the modifications, or have to modify the modifications.... you can have new copies of the original schematics made, but it's hard to remove the ink marks from the original manual pages (been there, someone else done that, had to redo some of his radio mods when we rebuilt the system, and I ended up buying a replacement Moto manual on eBay to get a clean schematics to make copies of...). And don't forget to put a one set of the marked-up Xeroxes in the master documentation book and a second set in the on-site documentation book!!
    Look in the Yellow Pages for a graphic arts shop, or a FedEx Office (was "Kinkos") chain copy shop, then call and see if they have a roll-feed copier. I had seven wide-page pull-out schematics in a Moto manual copied for about US$2.00 per page - and would have considered it worth it at twice that price. Or ask a local small Architectural business who they use for large format printouts / copies, then go there. Many graphic arts shops can do roll-feed copies and can print PDFs that are emailed to them or are brought in on CDs or USB thumb drives.

Sites and Site Preparation

1. The FCC has regulations on RF exposure. Wether you agree with them or not, the site owner / manager has to comply with them. At sites with broadcast equipment these regulations may require other building tenants to reduce their transmitter power while someone is on the tower. Broadcast stations do NOT like to reduce power, so if there is more than one broadcaster on a hilltop they usually coordinate tower work and power reductions among themselves. If you are at a broadcast site you will probably have to schedule your tower work with the broadcasting chief engineer(s) at his convenience, and what tower work you can do may be on very odd hours (minimum impact to the broadcasting cash flow) and on short notice.
   
   
2. At some sites you will pay a flat rental rate that includes power - you just plug your rack or cabinet into an open outlet and you are on the air. At other sites you will have to provide your own power meter. This means that you will have to hire a licensed electrician and he mounts the meter box on the wall and runs a conduit along the wall to where your rack will go, and mounts an outlet box. If this is the case you will have to budget for the electrician and the parts. Since you will have to mount a meter box anyway, and the smallest one I've seen will host 6 breakers, I'd put in two, and run two circuits. Then have two plugs whose cords lead into your rack, and split the load. Note that this arrangement will require two Isobars. And put a contact page on your meter box and padlock the breaker side of it. I saw one site where an amateur repeater was required to have his own meter and a few years later he found that someone had punched out a knockout, added a breaker, and ran a circuit from it to power some station equipment.
   
   
3. At some sites you will have free access - you will get your own key and have 7 days by 24 hours access. At other locations, like at the top of a building, you may be limited to business hours, i.e. Monday to Friday, daytime hours only. One site I know of is on the roof of a downtown building and is only accessible for one day twice a year when the elevator mechanic does his inspection. If something in the elevator control equipment needs fixing then there is additional access on the day he comes back to do the repair work, but that's chancy (yes, this means that if the repeater dies, it may be six months before you can do anything about it, even if it's just a blown fuse). Another sites I know of is owned by a 2-way company, and the owner will not give out keys - if you want to work on your equipment you go up to the site on the day(s) when an employee (that has a key) is going up to work on company owned equipment. And another site is accessed only through a pasture on a cattle ranch (private property). If a site visit is needed the trip has to be coordinated via telephone at least 24 hours before with the ranch owner so that the cattle can be moved, the gate(s) can be unlocked and those restrictions are written into the site agreement.
   
   
4. Ask about tower access (i.e. climbing the tower). Some sites don't care. Others limit tower work to site owner employees. Others have a list of outside folks that the site owner trusts... you can hire anybody on the list. Others allow you to hire your own tower monkey, as long as he is certified. Some just don't care.
   
   
5. Some sites require that liability insurance be purchased by each and every tenant. One million, two million or five million dollars are common numbers.

1. Buy a magnetic key box and put a spare key for the repeater cabinet in that, then hide it where it can't readily be seen. Some day you WILL forget to bring the site key ring with you when you're running late. This is especially important if another authorized person has access to the site but needs to get into the repeater cabinet.
   
   
2. Make sure a copy of the station license is on the equipment, as well as contact information for several people plus the operating parameters - receive and transmit frequencies, transmitter power, etc. And keep it current! If the area code splits, make a site visit and update the contact sheet.
   Note from WA6ILQ: First, if your have your own electrical power meter you will want to put a note on it stating that it is separately billed power for your rack (and which rack it is). Second, as far as contact sheets go, a common method is to make a xerox copy of the license at the top of a page, then type the contact info below that, then put the sheet into a page protector. A 9x12 inch piece of pexiglass is screwed to the front of the cabinet, and the page protector is sanwiched under that. As to "keeping it current", yes, I can take you to a site and show you a rack that has been place for over 25 years. It has a contact sheet on the front, and listing four people. Three have been dead for at least five years. All the phone numbers show an area code that I can recognize is two splits old.
   
   
3. Some basic hand tools in a toolbox are always useful. Include a small but workable soldering iron. Don't forget some solder and several feet of hookup wire in various colors. A small DVM can come in handy and can be found for under $10 in a lot of places (but leave the battery OUT of it until needed, and check the calibration before you trust it, I've seen cheapies that were 20% off on DC volts and over 15% off on AC volts). An extension cord / outlet strip might be necessary... you might have to do some work outside the building and if the only outlet in the vicinity has your repeater plugged into it (and that should be a twist-lock) you might be left scratching your head. Personally, one item on the take-it-to-the-site checklist is a 100 foot extension cord on a reel.
   Note from WA6ILQ: My "Take-it-to-the-site" tool box also includes a roll of gaffers tape (double strength and double sticky cloth duct tape), a roll of Scotch "88" electrical tape, pliers - "electricians", needle-nose, diagonal cutter and channel lock (to loosen stuck coax connectors), a retractible blade utility knife, and both standard and phillips screwdrivers. A blue multi-bit screwdriver is under $3. Everything but the tapes can be acquired from Harbor Freight. Yes, I know it's poor quality stuff, but this set is for emergency use - it's going to be left at the site, and the plan is that you will have your good tools with you. And include a half-case of quarts of bottled water - enough for you (to drink and to clean up with) and, just in case, some for your vehicle (battery, radiator, etc.)
   
   
4. Paper towels, Zip-Loc bags, a real First Aid kit plus some extra Band-Aids, a couple of clean rags, a roll of TP, some bottled water. Some burn ointment for when you slip with the soldering iron. This kit is more for cleaning up and dealing with nature calls, especially if the site has no bathroom or other facility. Watch for an empty metal first aid box (Red Cross, Zee Medical, Johnson & Johnson and others make them) at a garage sale, give it a coat of white paint, add a red cross with a can of red paint and a mask made from newspaper, then restock it with what you need. You can use it for site trips or for public safety events.
   
   
5. If possible, try to get your repeater on its own circuit breaker with nothing else on it. You don't want your repeater to go off the air when something else, on the same circuit, but a different outlet, blows up.
   Note from WA6ILQ: been there... our system died one day, and a hill trip found an adjacent cabinet where the input filter cap on the main power supply had shorted and detonated, and blew the AC mains breaker. We found the AC input fuse on that racks main power supply wrapped in foil. Apparently the system had been blowing fuses for a while and someone got tired of hill trips to do nothing but change a fuse. I called the contact number posted on the rack, got hold of the owner (at work) and let him know what I had found. I then unplugged his rack and reset the breaker. On my next hill trip I brought along a club member's brother who was a licensed electrician, we popped a knockout in the panel and added another breaker and a separate outlet (a twist-lock) for our rack. I didn't want to trust anyone that solves intermittent problems by wrapping foil around a fuse.
   
   
6. Have a maintenance log book at the site, and an exact duplicate in your toolbox, in which you write down the date and time of each visit, what was done, and by whom. You never know who might end up going to the repeater when you're away on vacation and they need to reset the squelch that you loosened the week before. Baseline meter readings are also great for determining when something is going sour. If the repeater is using commercial equipment, metering test points may already be available. At a minimum, record the forward and reflected power going to the antenna, and note the DC resistance of the feed-line and antenna, so you can tell if something shorts or opens. Why a duplicate? Because there will be times when you can't remember if you did or did not do something. If there is more then one person that maintains the repeater make a point on each visit of checking the on-site logbook and updating your personal copy. Be a very annoying perfectionist on one topic: keep your personal toolbox copy and the site copy exact duplicates - so that if is there is a question you can look at your toolbox copy and be sure of the answer.
   
   
7. If your club is a 501(c)3 tax exempt organization, do not forget to log your time and mileage on repeater maintenance and site trips. Depending on your state tax structure there are deductions available for your donated time and mileage. That's all I'm going to say, you need to check with your accountant / tax man.
   Note from WA6ILQ: And you might want to see what it takes in your jurisdiction to have your group get tax exempt status. One local group is a 501(c)3, and back in the late 1980s was able to get a donation of 50 GE MASTR Exec IIs with heads, cables, microphones, etc. strictly becasue they were a 501(c)3. The neat part was that every single one had a TS-32 CTCSS board in it. They were worth more than the radios were...
   
   
8. If you can acquire them, leave duplicate documentation / manuals for the equipment in the bottom of the rack cabinet, mainly of the repeater controller, but leave something there if the repeater radios have functioning control panels (but keep the master copies at home). The duplicates are more for quick troubleshooting at the site, but also handy for that oddball situation when the controller has gotten reset and you need to tell it which rarely-used functions to enable. If the controller can be loaded by a computer program it's worth leaving a floppy or a CD with the upload program and the data file. At least make up a "cheat sheet" listing the bare minimum commands to key in to make the system useable and remotely programmable.
   
   
9. If you ever notice water on the floor at the site, find out where it is coming from, notify the site owner, and then elevate your equipment on bricks or cement blocks "just in case"... Take care that the manuals you left on the bottom of the rack can't get submerged or otherwise damaged by anything dripping down from the equipment above - be it roof leak water, condensate from an air conditioning system, or the drippings from a leaky capacitor.
   Note from WA6ILQ: 9x12 inch (and even larger) Ziploc bags are available and make dandy waterproof and dustproof "envelopes" for manuals and other documentation. And it might be worth putting the rack up on blocks (maybe 3 to 4 inches high) to start with...

Miscellaneous

1. Put an AC powered light in the top of the cabinet (open frame racks don't need as much light), and maybe a fluorescent or LED tube light (a small version of the "trouble lights" the auto mechanics use) in the toolbox. A good low profile one for the top of the cabinet is one of the circular fluorescent lights. You can put an in-line switch in its cord and plug it into one of the unswitched outlets mentioned above.
   
   
2. If your site has a phone line and your repeater controller has an autopatch option consider buying it (even if it's not for member use) when you acquire the controller. Even if your controller doesn't have a patch you will want to put an old Trimline or Princess phone in the bottom of the cabinet, and wire it to the phone line. If something should happen to you at the site you will need to be able to call for help. Having a working dial tone in the cabinet gives a nice warm fuzzy feeling.
   Note from WA6ILQ: Most of my sites are on hilltops in wilderness locations, anywhere from 10 to 30 miles from the nearest paved road, and just as many miles from the nearest cell phone coverage (yes, I may be standing at a tower base on top of a 5,000 foot mountian and have a radio horizon to dozens of cell sites but every phone I've had on a hilltop - no matter what frequency, no matter what carrier - shows NO SERVICE). Due to these reasons I try to NOT make site trips alone (and definitely if the to-do list includes tower work). At a couple of sites the in-rack phone is piggybacked on an adjacent rack's phone line (with permission). One of the first things I check when I arrive is if I have dial tone. And not one cordless phone I have tried works on a mountaintop. Must be all the RF in the air.
   
   
3. Time... every repeater project always ends up taking a lot more than you expected. The standard rule is that the first 95% of any repeater project takes 95% of the time, and the last 5% of the project takes the other 95% of the time (if not 195%).
   
   
4. Money... Every repeater project always ends up costing a lot more than you expected.   Whatever budget you think it will take, double it.   That still may not be enough. Sometimes you find that the standard rule mentioned above about time also applies to money.   If your club is going to build a high quality repeater (and is it really worth building anything else?) you will need to spend some serious financial resources to the project.   Make sure your club members are committed and won't back out halfway through.   And prepare them for unexpected surprises: one project that I am aware of ended up costing five times the original budget (they had planned on re-using the circulator, duplexer, feed-line and antenna, and couldn't, and had to buy all new, plus hire a tower climber approved by the site owner).   An acquaintance, a retired US Navy SEAL, once made a comment on another project (a restoration of an old Corvette) but his words apply here "Don't stick your neck out, until you know that your body can follow and you're not going to be shot at."
   
   
5. Keep a few 3x5 cards and two pens in your shirt pocket when you go to the site (the second pen is to use after you leave the first somewhere). You will think of things and you will forget them before you get home. One of these light-bulb moments resulted in my picking up an old card table from a thrift store for $1, and strengthening the top with a piece of 3/16 inch Masonite. The repaired table became part of the "site tool kit" (think of it as a throwaway workbench that can be folded up and left in a corner). Eventually I decided to leave it at the repeater site, wrapped in a trash bag to keep it clean (and once I found a note of thanks taped to it).
   
   
6. This item is from a friend that had this happen... he usually carries a bank card or two and minimal cash... and his 4x4 has rain gutters and he has a set of Yakima roof racks that he clamps on when he needs them...
   His suggestion: have a checklist of things to take to the site that normally don't live in the vehicle or in the take-it-to-the-site-toolbox... like your digital camera, a 100 foot extension cord reel, the field glasses (for doing a visual check on the feed-line and the antenna) plus the clamp-on roof racks for the vehicle (and the ammo can full of elastic cords to tie things to the racks). Keep that list in the toolbox, and check it every time that you grab it. Murphy's Law says that you will need the camera, roof racks or the field glasses the one time that you don't have them with you. One thing that you probably won't think of is to stash an envelope in the bottom of the tool kit with enough cash to cover replacing a tire... or two...
   On one trip he was on the highway that leads to the site road... he hit a piece of debris on the highway that severely damaged the right front tire. He limped into a truck stop and bought a new tire. The shop wanted cash, not a bank card, and the ATM in the truck stop was out of cash. He ended up walking about a mile and a half to the nearest teller machine, getting the cash and walking back. When he got to the site there he found the site owner supervising a tower crew that was stripping the tower of old unused antennas and feed-line... when he arrived the crew had just finished cutting up several dipole arrays and cutting the old feed-line into 10 foot sections to fit in a long-bed pickup. If he had the racks on the vehicle and arrived there an hour or two earlier he could have scored several 8-pole and 4-pole arrays and several 100-150 foot coils of 7/8 inch Heliax feed-line.
   
   
7. If you have your own building, or your own room in a building (or even room for a second cabinet at a site at no charge) then consider stashing a sleeping bag or a couple of blankets, plus some food and water in a mouse and rat proof box. There's a classic story about two guys that arrived at a mountaintop radio site in clear fall weather without a cloud in the sky and worked from 7am until 6pm stopping only for a sack lunch, staying inside where it was warm. They finished the job and walked outside and found snow on the ground between one and two feet deep. If they hadn't been in a 4x4 Suburban they would have been stuck. As often as you'll need it, maybe an electric heater would be good as well. Yes, they can be expensive to operate (according to the DOE retail electricity prices can vary from as little as 4 cents to as high as 45 cents per kilowatt-hour, but as often as you'll need it that heater just might be what keeps you from suffering through a very cold night...).
   
   
8. If your vehicle came with a mini-spare then go to a junkyard and get a full sized rim and get a good used tire put on it at a tire store. Even if the road to the repeater site is good graded dirt I won't take a mini-spare off road.

% From Vincent N6OA:
% Don't forget the creature comforts like a heater for winter and a
% fan for summer while you are working. A gallon bottle or two of
% drinking water, some foil-wrapped granola bars, a roll of paper
% towels and a roll of TP (just in case). Stash some special tools
% and common parts all in a locked box. I always forget to bring
% something so have made special allowance for such things and
% keep it at the sites. I just hate to drive 100 miles round trip
% for a roll of electrical tape.
% ...been doin' this for 50 yrs this year....and you'd think that
% by now I'd know better.

Comment on the above from WA6ILQ: Make the lock on the box something that you always keep a key for on your daily key ring. My local locksmith sells bubble-packed sets of three Master padlocks keyed alike for a low price. You could use one from the set on the repeater site toolbox, a second on the gate at your house and the third on the toolbox at the other radio site. Nobody needs to know that the gate key on your personal everyday key ring fits the radio sites... This way you never forget the key to the repeater site toolbox. Been there, done that, had to hacksaw the lock...
Another "lock trick"... Do you have a situation where an important padlock gets left unlocked? Perhaps the one on the site gate? Almont company makes a "ReKey" line of padlocks, available from any good locksmith (not every locksmith stocks them, you will want to call ahead before you drive across town). The Almont is a heavy duty brass padlock that is of much higher quality than any Master lock and has two useful features: 1) it is a "captive" design: you can't remove the key unless the lock is securely locked. 2) the manufacturer makes cylinders for Kwickset, Schlage, Best, and most of the other major keyways, so it can be keyed to an existing key on your key ring, meaning that you now have one less key to worry about and keep track of. It's more expensive than any Master brand lock but depending on your local circumstances it may be worth knowing that nobody but nobody can leave it unlocked - like on that site road that goes through the cattle pasture... you don't want the landlord complaining that his cattle got loose. As a price point of reference, in January 2006 I purchased an Almont ReKey for a client location and the out-the-door price for the lock in hand and pinned to match an existing Schlage key was US$25 plus local tax.

From a long-time repeater owner, on the topic of sending TCXOs to International Crystal for rebuilding instead of doing it himself):
Frankly, looking at the big picture, with gas at over $3 a gallon and my owning a vehicle that gets about 18 miles per gallon (about 7.6km/l), I can easily cost-justify the extra $25 to make sure it's always "done right", since my closest repeater is a 50 mile (about 80km) round-trip from the house, and the furthest is over 100 miles (about 160km) round-trip.   "We can go back up and fix it later" just isn't in my vocabulary anymore.

Don't forget:

• If you have the rack space (and not everybody does): A thru-line wattmeter left in line permanently (something like a rack-panel Bird wattmeter or similar). Note the initial numbers on a 3x5 card taped to the front panel. By knowing the starting numbers you can see any changes from site visit to site visit. If you has a reepater controller with an analog input then you can connect it to the Bird element output and read it remotely. If you have the model that has two line sections (i.e. two elements) allowing reading simultaneous forward and reverse then you can connect both of the the analog voltages to analog inputs on the repeater controller.
  
  
• Good AC power distribution inside the rack (a commercial grade power strip). See comments above on Tripp-Lite Isobar power strips.
  
  
• Good AC power coming into the rack. The site manager is responsible for this, but you should do a good look once in a while. For example, the Federal Pacific (also known as Federal Electric) brand of power panel is an orphan and you can't get breakers any more. FE / FP is out of business because they lost their UL rating due to poor quality... FE / FP breakers had problems with not tripping when overloaded, plus there was inadequate buss-bar contact resulting in overheating inside the panel. Challenger Corp. makes FE / FP compatible breakers but that doesn't fix the bad panel design, and some insurance companies won't allow "foreign" or remanufactured breakers... If they even allow FE / FP panels then it's either original FE / FP breakers or none at all.
  
  The half-width breakers (of any brand) are to be avoided if possible as they have only half (if that much) copper connecting to the buss bar in the panel.
  But again, this "problem" is the responsibility of the site managers / site owner(s) (and his insurance company).
  
  
• Backup power (UPS, backup battery/charger, etc). If you use gell cells note the manufacture date (or purchase date) of the battery with a Sharpie on the outside of the cells and change them out every few years. Some battery makers hot-stamp the manufacture date on the battery, some don't. If you can't determine the manufacture date just assume that they were 6 months old when you bought them.
  
  
• Quality DC power distribution (I've been standardizing on eitehr Blue Sea or Duracomm BB series fuse blocks, although the West Mountain Radio "Rigrunners" are nice with the Anderson power pole connectors built-in... but they refuse to make a rack-mount version... West Mountain Radio: are you listening?)
  
  
• Quality RF, audio, telco, power, DC, etc. interconnect cables. If you don't know the history (especially on the RF coax and the connectors), be suspicious.
  
  
• The biggest single thing: obtaining a worthwhile site at an affordable price!

Contact Information:

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.

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Article written 2005

Original page designed by Doug Fitts, W7FDF and Copyrighted © 14-March-2001, expanded on with permission from Doug by Mike Morris WA6ILQ November 2005.
Contributions credited in the list above.
New text, artistic layout and hand-coded HTML © Copyright 2005 and date of last update by Mike Morris WA6ILQ

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.