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Parts List and Check List
Originally by Doug Fitts W7FDF
Contributions from Vincent Mc Kever N6OA, Robert Meister WA1MIK,
Jeff DePolo WN3A, and Nate Duehr WYØX
Edited and HTML'd by Mike Morris WA6ILQ
Maintained by Robert Meister WA1MIK
When one goes out and builds their first repeater, it seems like a daunting task... all
the parts and related items you need... so here's an attempt at creating a list. Note that
the repeater rules vary from country to country. What is legal in one place will in many
cases get you in trouble elsewhere (for example, Australia has extremely restrictive autopatch
rules, and in the UK a repeater has to ID every 15 minutes 24x7). The staff of this web site
is familiar with USA rules, and the bulk of the information at this web site reflect that.
We assume no responsibility for anything YOU do.
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:
The "Finding a permanent home" step in the above list should be number 2, but unfortunately
most folk wait until that stage or sometimes even later. I know one guy that waited until
just before the "Transporting the cabinet" step, and he ended up selling off the complete
repeater three years later simply because he couldn't find an affordable site that had the
"antenna footprint" (the geographic coverage) he needed, and he didn't want to break
the bank or have to end up taking out a loan to simply be able to afford it.
- The decision that another repeater would be a good thing.
- Acquiring parts.
- Mounting all the parts in an open workshop rack.
- Locating smaller parts since not everything fits.
- Making the assembly of parts work as a unified whole.
- Rebuilding parts or locating replacement parts since you don't discover that everything
doesn't work together until you power it up.
- Making the new collection of parts work as a unified whole.
- Spending hours and hours programming and reprogrammin the controller to get it "just right".
- Beating the final gremlins into submission, including the intermittent that only shows up
at 4am on fifth Sundays during a full moon.
- Finding a permanent home for the new repeater, and envying those that get their sites for free.
- Taking the wife out to dinner a few times to make up for the evenings you spent in the workshop.
- Preparing the site (backup battery bank (if needed), tower-mounted antenna, feed-line, etc).
- Installing the repeater, item by item, into the permanent cabinet rack.
- Making longer cables to replace the ones that no longer reach.
- Making everything that broke work again.
- Transporting the cabinet to the repeater site (which may require borrowing a 4x4 vehicle).
- Fixing what broke during transport, including retuning the duplexer.
- Spending several evenings and weekends beating the last gremlins into submission.
- Taking the wife out to dinner a few times to make up for the evenings and weekends you
spent at the repeater site.
- Formal announcement that the repeater is on-line and available.
- Locating and fixing the intermittent that only shows up at 4am on fifth Sundays during a
- Listening to the users whine that they can't "get in" with their fleapowerd HTs from 100
- Listening to the jammers.
- Listening to the users whine about the jammers.
- Listening to the other users whine about the users that whine about the jammers.
- Taking the wife out to dinner a few times to make up for the evenings and weekends you
spent at the repeater site.
- 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.
- Becoming a repeater user yourself for a few years.
- Realizing that having another repeater would be a good thing.
- Repeater main channel receiver, on the proper frequency 1,3,5
- Repeater main channel transmitter, continuous duty rated, on the proper frequency
- Duplexer 11
- Isolator or circulator 9
- Notch / Band-pass filter
- DC Power Supply 2
- Battery bank and charger (optional) 2
- Connectors and coax (see 6,7 and 8 under "Construction")
- Antenna(s), plus any necessary mounting hardware
- Lightning Arresters / Suppressors (Huber & Suhner, Polyphaser, etc) 3
- Grounding System / Equipment
- Rack or cabinet 4
- Control receiver and appropriate feed-line and antenna
- Link receiver(s) and transmitter(s) and appropriate feed-line(s) and antenna(s). In
some cases duplexers on the link frequencies may be required.
- Support electronics (see below)
- 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
- 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 200ah battery may only have a usable 100ah).
Some folks just build a complete 12 volt-based system, and power it from a
common 12v golf-cart 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 about
15 minutes of loss of power, especially if the site is notorious for bad power.
This UPS will also keep your repeater running between the time commercial power
fails and 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). Note the manufacture date of the UPS
internal batteries (or of the UPS itself) 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)... 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‑voltage shutdown operational. Test your UPS on low voltage
AC, what will it do if the AC line voltage drops to about 70 volts? If the
power company loses a phase on the line that goes up the hill that's what
your AC voltage will be...
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 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 100w
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 62 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 62 as a magic number); the UPS should charge the battery with whatever comes
in, and make 60 Hz going out.
If you are using a site battery‑based system, pay extra attention to the
charger and the Low Voltage Dropout unit. Use a top‑quality, automatic
one, 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.
Watch out for the occasional device that needs a weird supply voltage - for
example the GE Voting panel uses 120vAC or 28vDC, and some higher power
transmitters (the MTR2000 repeater 100watt PA deck is one, the high power
MSF VHF repeaters are another) use 24vDC. GE has a 12vDC-to-28vDC inverter for
their voting panel, Motorola hasn't had any DC-to-DC converters in their
catalog since the transition days from 6v to 12v vehicles. The end result
is that you may end up running the battery bank as 24v or 28v and using a
24v-to-12v inverter to power the rest of the rack, or even running two
separate strings of batteries with a common negative, one on 24v and one
on 12v, 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 over charged
and the ones below the tap will be undercharged. Both situations will kill
the batteries 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. 120vAC) 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 120vAC to about 70 volts AC and see what happens. What's so magical
about 70v? 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 (onto 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 95vAC). 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 +12vDC and +5vDC down to 50vAC.
- If you plan on putting your system at a high RF level or commercial 2-way site, you
should use a receiver designed for use in a repeater as it will be equipped with tunable
helical resonator front ends and not the no-tune wide-band lumped LC found in the cheaper
mass-produced amateur radio or the low-end 2-way market.
In other words a common single-bander or dual-bander amateur mobile radio is not
appropriate for a high level RF site as a primary receiver. The front end is just too
broad and hence has very little rejection of off-frequency strong signals that will
cause receiver desensitization or blocking. Another reason to avoid synthesized radios
is spectral purity. You might think that crystal technology is old hat but it is just
what you need for a repeater as the signals generated from crystals are much cleaner
and purer spectrally unless you have one of the very best synthesizers (and besides,
how often does the repeater change frequency?) This is important as noise sidebands on
the transmit signal and the receive local oscillator contribute to receiver de-sensing
or blocking and when the transmit signal is only 500 kHz away (6 meters in some areas)
or 600 kHz (on 2m) away your receiver needs all the help it can get! UHF is a bit more
relaxed as it's usually 5 MHz away.
And spectral purity affects receivers as well. The front end feeds a mixer, which combines
the multiplied local oscillator and the incoming signal to produce the first IF frequency.
Any spurious signals in the output of the local oscillator result in hearing an additional
signal for every spur. Synthesized radios have been around since the 1970s and by now the
design is mature, but to this day you will find that most amateur repeaters are crystal
based. There must be a reason, and it's not just purchase price - it's also spectral purity.
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 "site battery bank" you
can tap into, others will let you put a Rubbermaid 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
and build your system around them. You may find this web page relevant:
A Sample Set Of Radio Site Rules.
- 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
one at under $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 bands 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. All it took to see it was shaking the
cable - all sorts of cracklies happened and desense would go through the roof or totally
- 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 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
- 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, and in over eight years 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).
- 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".
- If you are using programmable radio(s) in the system you might want to have a
floppy disk 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).
- Every transmitter needs a ferrite isolator between the output connector and
the next item in the antenna system - be it a duplexer, or an antenna. An isolator
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 circulator is an isolator 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 100watt 2m
or UHF MASTR II continuous duty station power amplifier recently?
- 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 includes
EchoLink or IRLP... 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 a reflector
then everybody on every node hooked to the reflector.
- 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 I have seen an 8-cavity one (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. Be suspicious on any inexpensive used duplexers - I
have seen used ones that have arced over internally and need replacement glass piston
capacitors that are $100 each. Do your research before laying down your money to buy any
duplexer. And you may not need a duplexer - split sites are possible. A good system
can be built with no duplexer at all.
- Repeat audio output from each receiver, filtered for 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. Some systems have two or three PL tone
- 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.
- 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 service restoration after a disaster. If you do get an
EM sponsored phone 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.
- 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 cross-point
audio matrix from the receivers to the transmitters. See the drawing at
and count the number of point-to-point links arriving at Santiago Peak (pronounced
Son-tee-ahh-go).... and the links are a mix of 420 MHz, 439 MHz, 900 MHz,
1200 MHz, microwave and VoIP. And after you count all the links remember that does not
include the 6m and 2m remote base or the local user repeater.
- 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.
- 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.
- 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.
- 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. If you can get them, two‑contact trailer power
connectors with a decent wire size work well, plus they plug directly into MaxTracs,
Spectras, Radiuses and similar radios. Either make up a DC power panel with 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. Good source of DC breakers are 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.
- 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.
- 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.
- 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.
- 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).
- 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.
- 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
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.
- 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
- 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.
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
So before you sign the rental contract make sure that you can live with any site limitations.
- 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.
- 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.
- 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.
- Ask about tower access. 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 sites require that liability insurance be purchased by each and every
tenant. One million dollars is a common number.
The rest of this section, plus several other notes on this page, is by Robert Meister, WA1MIK
- 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.
- Make sure a copy of your license is on the equipment, as well as contact information
for several people plus the operating parameters - power, receive and transmit
frequencies, 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. 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.
- 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. 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.)
- 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.
- 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.
- 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.
- 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 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...
- 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.
- 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
- 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
- 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
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.
- 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%).
- 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."
- 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" 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).
- This item is from a friend that had this happen... he usually carries a bank
card or two and minimal cash... and his car 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.
- 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...).
- 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.
- 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 get the type 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 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 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!
The author can be contacted at: his-callsign // at // repeater-builder // dot // com.
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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
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