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  Beginner's Guide to
the MSF5000 Station

By Robert W. Meister WA1MIK
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This sort of real "beginner" information is sadly missing, although I would hardly call an MSF5000 an entry-level station. Sometimes amateur clubs get equipment donated, and some unknowing ham gets stuck trying to make it work. Since the repeater-builder site's primarily mission is about building repeaters, I will attempt to detail the equipment and useful things you should know in order to:

  1. Determine what you have (analog vs digital station) and why you want the digital station (which the article will be aimed at)
  2. Set up a programming environment (computer, RSS, cables, RIB)
  3. Work on the station (required and handy tools)
  4. Gather the necessary test equipment
  5. Access the station for alignment or repair
  6. Program the station
  7. Align the station
  8. Troubleshoot error codes
  9. Convert a base station to a repeater
  10. Interface external controllers
  11. Make the repeater FCC-legal (i.e. the minimal control requirements and what the internal controller can do)
  12. Properly ground and protect the station from disasters
  13. Provide power to the station
  14. Miscellaneous items

There are no photos, images, or other graphics in this article, but there are a lot of links to other articles and PDF files primarily in the MSF and PURC section of the site.

Determining What You Have:

The first thing you need is the model number, usually found on a tag on the right side of the station. You can then decode it by viewing the table in the MSF5000 Photo Tour article. You'll need a standard Motorola 2135 key to open the cabinet. You should be able to identify the major internal components; read the Photo Tour article.

There are two types of stations: analog, which requires a suitcase programmer to change the code plug parameters, and digital-capable (which will be called digital in this article), which requires an IBM PC and other stuff for programming. The analog stations are those that have "CLB" in the model number; the digital stations are those that have "CXB", RLB", "GFB" or some other letters. The digital stations have a three-digit, seven-segment display at the right side of the control tray; the analog stations do not.

There are also paging (transmit-only) stations with the name PURC5000 that are based on the analog MSF5000 stations and have "JLB" in the model number. Many of the topics and techniques in this article can be utilized on those stations.

If you see the sequence "SPnn" at the end of the model number, this means it's a Special Production version that's different from the normal station. Some section has been modified or a feature has been added that's not present on a standard station. Documentation is usually included with the station and if it's not there, you can forget about it. Sometimes the SP modifications can be reversed or removed.

Primarily due to the ease of making programming changes, the digital station is the one you really want to work on. The hardware is nearly identical but the control tray, versatility, and flexibility is the main benefit.

Programming Environment:

The analog stations utilize an R1800 or R1801 suitcase programmer. Besides the basic programmer hardware, you will need the proper EPROM adapter plug-in module, the program ROMs that are aware of the MSF5000, some way to erase an EPROM (an ultraviolet eraser), and of course one or more 2732 EPROMs to program. All the parameters are entered into the suitcase programmer through its membrane keyboard and single-line display. The proper information is written to the EPROM and you install that into the Station Control Module (SCM) in the Control Tray of the station. Not many of these suitcase programmers are still around, so to save yourself the aggravation and cost, it's easier to avoid an analog station. But if you're stuck with one, I suggest you send the EPROM out to one of the people listed on the MSF and PURC Index Page in the Analog Station Programming Services section. Note that there are TWO EPROMs in the SCM: one contains the program (labeled "PROGRAM") that instructs the microprocessor; the other contains the code plug data (labeled "CODE PLUG) that defines the operating parameters. It's this second EPROM (U803) that you need to work with; it's the one closest to the corner of the SCM, has "CODE PLUG" stenciled above it, and is usually smaller than the program EPROM. Pin 1 is towards the front of the station.

The digital stations are much more user-friendly, however they require several external components to be successfully programmed. You will need to install the correct Radio Service Software package (RVN-4077) on your hard drive; this software is No Longer Available (NLA) from Motorola; do not ask me for it. Search the web; several foreign sites have it. You will need an IBM PC; almost any speed will do. It must have a real 9-pin or 25-pin serial port; a PCMCIA or USB serial port adapter will not work. The computer must be capable of booting to MS-DOS; the software will not run properly in a DOS BOX or under Windows. I use a laptop computer running WinXP on the hard drive formatted for FAT32, then I boot to MS-DOS on a floppy disk and run the programs stored on the hard drive. You will need a Radio Interface Box (RIB), an appropriate cable to connect the RIB to the serial port on your computer, and an appropriate cable to connect the RIB to the MSF5000. The MSF5000 Programming Cable article has details for making your own RIB-to-radio cable. Many after-market RIBs come with a serial cable. Read about RSS and RIBs on this page.

You can use either the modular Control jack on the front of the control tray or the expansion connector on the top of the control tray for programming, however if you have an MSF5000 metering panel (described shortly), that unit can only plug into the expansion connector on the top of the control tray, so you're really better off using the modular jack on the front for programming.

Required and Handy Tools:

Motorola sold a tuning tool kit that contained the tuning probe cable, 5mm hex wrench, and several other plastic and metal tuning tools. The MSF5000 Photo Tour article has a photo plus a better description.

Gathering Test Equipment:

You will need good test equipment if you want the station to meet specifications. That old tube RF generator you bought in the 1960s just isn't going to hack it. I purchased individual pieces of professional equipment, but most communications service monitors have all the abilities you will need in one easy-to-carry unit. Either way, it could be a substantial investment, even if you buy on the used market. If you don't have this equipment, find someone who does who can either do the job for you or assist you. Most people will be hesitant to loan out expensive and easily damaged test equipment. All it takes is for you to transmit into the receive port of a signal generator and it's toast.

You'll also need various coaxial cables with appropriate adapters to attach to the transmitter and receiver antenna jacks on the station. I use RG400 (double-shielded) cable with male BNC connectors, plus the appropriate BNC to N male adapters, for the receiver, and RG214 (double-shielded) cable with crimped-on male N connectors for the transmitter.

Motorola made two metering panels for the MSF5000 product line. Both have a 50 microamp meter, meter polarity switch, meter signal selector switch, loudspeaker, and audio amplifier. The Radio Metering Panel (RMP) TLN2418A unfortunately stops there. It's OK for alignment purposes but not much else. You really want the Diagnostic Metering Panel (DMP) TLN2419A, which adds an array of 64 LEDs that tell you the status of 64 logic signals inside the station. You can also activate many of these signals manually through front-panel switches, and this ability greatly simplifies the alignment procedure. You'll need two cables that should come with either meter: a 40-pin flat cable for power, audio, and logic signals that plugs into the expansion jack on top of the control tray, and an 8-pin modular cable for metering that plugs into either the RX or TX metering jack on the front of the RF Tray. A set of test probes should also be included but they usually get lost and you're better off buying and using a digital multi-meter instead. Photos of the DMP are in the MSF5000 Photo Tour article and the manuals for each are available at the bottom of the MSF and PURC Index Page.

You could use an ordinary 50 microamp meter and a modular network cable to make your own metering test set, however you'll eventually want a real MSF5000 DMP, so start looking around for one.

Accessing The Station:

These stations are HEAVY: 150-300 pounds. Two people are required to move one. I recommend you elevate the station at least 2-3 feet above ground by putting it on three layers of cinder block or up onto a stable work bench.

Use the key to unlock and remove the front door. Locate the RF Tray; it's usually the lowest unit in the cabinet and it will have "MSF5000" printed on the front panel. Refer to the MSF Photo Tour if necessary. Use a Torx wrench to remove the four screws holding the front panel of the RF Tray to the cabinet side rails. Put your fingers into the two spring-loaded plastic latches at the bottom corners of the RF Tray's front panel and slide the latches toward the center of the station, then pull the RF Tray forward. It's on equipment slides and should pull all the way out, about 8-9 inches.

The plastic control tray is mounted on top of the RF Tray. There may be a second plastic expansion tray on top of the control tray; treat them as one assembly for now. To access the top of the RF Tray or work on the control tray, first you have to unlatch the control tray. On the left side there's a plastic latch. Push the top inward or pull the bottom outward just a bit while lifting the left side of the plastic tray. Be very careful as you lift it all the way up. There are three easily broken plastic hinges on the right side that the tray pivots on. A sliding guide at the rear of the control tray will limit the travel to just over 90 degrees. As long as you've extended the RF Tray all the way out, the control tray will clear the RF power amplifier. You can now access the various adjustments on the top of the RF Tray or even remove its top cover. This condition, where the RF Tray is extended and the control tray is raised, is known as the "service position".

You may notice two large knobs in the rear corners of the top of the RF Tray. These activate mechanical locks on the two VCOs to keep them from rattling around when the station is being moved (TRANSIT position). The station will work with the VCOs locked or unlocked, but they will float and be much less susceptible to mechanical vibration if they're unlocked (OPERATE position). You can see these in the MSF Photo Tour.

When you're finished, carefully lower the control tray. Don't let it drop; the plastic WILL break. Make sure none of the cables are in the way as you lower it. Also make sure the sliding guide at the rear of the control tray doesn't bind or get stuck because it WILL cause the control tray to twist and you'll very likely break one or more of the three weak hinges on the right side of the control tray. Lubricate the sliding guide if necessary. Secure the latch at the left side. Slide the RF Tray back into the cabinet until the plastic latches in the lower corners lock it in place then reinstall the four screws in the corners.

If you have to get to the power supply, you need to remove four screws holding the RF power amplifier first, then tilt the RF power amplifier out and down. There are pivot pins at the lower edge. Be careful; the PA weighs close to 40 pounds. The power supply is behind it. There are several fuses on the distribution board at the top of the power supply. Some stations have round glass fuses; others have flat blade (automotive-type) fuses. If that board has a shielded area, a slide switch, and a potentiometer, you've got a battery-charging or battery-reverting power supply.

Programming The Station:

Connect a dummy load to the transmitter or antenna output, just in case the station wants to transmit. Apply power to the station.

Start your programming computer. Attach the RIB to the computer and turn them both on. Plug the other cable into the station. Start the MSF5000 RSS program.

You should always read the existing code plug from the station and save it to disk so you can restore the existing settings. Always use a unique name. I suggest a date and possibly sequence number be used until you get a configuration that works to your satisfaction. You can delete the intermediate files once you've got things working the way you want.

After making changes, save the code plug to disk with a different name, then write the code plug to the station. Note that this happens in two phases: RSS sends the data to the station where it is stored in RAM. RSS then tells the station to commit this to EEPROM. The station automatically resets when this has completed.

This article takes you through most of the settings for a UHF repeater.

Aligning The Station:

The alignment section of the MSF5000 Instruction Manual has been scanned and is available on repeater-builder. It's rather long (48 pages) and has a few errors and omissions. You need to read it very thoroughly and follow the steps precisely. Some steps are skipped for some bands. I'd suggest you print the entire file and keep it near the station during alignment.

Perform all steps in each section exactly as they tell you to. Do not repeat a step without starting from the beginning of that section. For example, when tuning the receiver front end, adjust each coil going from left to right. Don't go back and readjust one unless the procedure tells you to. Also, in some steps you will be tuning for a dip or minimum. This should be very noticeable and you can rock the tuning screw back and forth to find the lowest point. Keep the meter between 15 and 25 so you can see the dip.

When adjusting the receiver (RX VCO, pre-selector and injection filter, front end), you will need a signal on the receiver's frequency and the meter cable will be plugged into the RX METER jack on the front of the RF Tray. When adjusting the transmitter (TX VCO), the meter cable will be plugged into the TX METER jack on the front of the RF Tray. The MSF5000 meter is not needed to adjust the UHF internal filter/duplexer nor for any of the electronic adjustments (mechanical potentiometers) in the RF Tray.

If you will be tuning a UHF internal filter/duplexer, note that one important instruction is absent from the alignment procedure: you need to connect the tuning probe cable (the same one you used to align the receiver front end) to an RF Millivoltmeter or spectrum analyzer as an indicating instrument. The probe end gets inserted into the various holes in the filter/duplexer casting in the same way that it gets inserted into the receiver front end.

If your UHF station has the internal filter/duplexer, you'll find it much easier to access the connectors if you remove the metal cabinet from the station. Use the Torx wrench to remove all of the bolts in the plastic top cover and remove the cover. Then apply slight outward pressure to the front of the cabinet while slightly lifting it up out of the grooves in the base. You can then bend the cabinet enough to clear the connectors at the right side and entirely remove the cabinet.

The forward and reflected alarm trip points should not be adjusted on VHF or UHF stations. On 800 and 900 MHz stations you can change these through the RSS service screen. You may see steps that tell you to set a particular MUXBus bit. This can be done through the RSS MUXBux screen or with a Diagnostic Metering Panel (DMP) by setting the appropriate address and data bit with the rotary knob and toggle switches then raise the "ENTER" switch to set that condition. Set the data switch off and raise the "ENTER" switch to clear that condition.

Electronically Eraseable Potentiometers (EEPots) are digital resistors with 100 steps or values of 0 to 99. These are what the digital station uses to adjust the audio and squelch levels. They can be accessed through the RSS service screen or by using switches on the front of the station. This article tells you how to adjust the EEPots. The analog station has ordinary mechanical potentiometers for the various audio and squelch levels. These are accessed through the front of the control tray.

Be careful when physically adjusting pots on the RF Tray. Don't push in too hard. Some of the pots are not mounted well, mainly the ones you access through the front panel.

The Modulation Compensation adjustment requires you to see the demodulated waveform. An oscilloscope connected to a deviation meter will probably work, but due to the low frequency utilized, a service monitor is much better for this procedure. It's not a critical adjustment and can probably be ignored unless someone has replaced parts in the RF Tray.

You can ignore the wire line adjustments unless you'll be using them to interface an external controller.

The squelch adjustments are particularly important. If you're going to be using the internal controller to generate the CW ID, the station will not send a CW ID if any of the squelches remain open. They must all be closed, whether you're using them or not, to enable transmission of the internally generated CW ID. The station will work fine in all other respects however.

Troubleshooting Error Codes:

The MSF5000 performs extensive diagnostics when powered up. If a problem is detected, a code will appear in the display window. This file decodes the errors and suggests possible corrective actions.

If the station has a real serious microprocessor error and it can't display an error code, it will blink one of the LEDs on the front panel. Also, the stations can send alarms out over the air as a sequence of beeps. There's a list at the end of this file that tells you those LED patterns and beeps.

You can enable or disable over-the-air error reporting (beeping) with RSS. Similarly, you can enable or disable audio diagnostics with RSS.

Converting A Base Station To A Repeater:

The MSF5000 can be configured as a base station (single antenna jack with a relay to switch between the receiver and the transmitter) or a repeater. On the UHF repeaters, Motorola provided a filter/duplexer and special cable inside the cabinet that allowed the station to use one antenna for both functions. They work, barely. You're really better off with a real external duplexer. On all other bands they utilized real pass/reject duplexers.

Base stations have a low-pass filter between the RF Power Amplifier (PA) and the antenna relay. On VHF stations, the antenna relay is installed in this filter enclosure; on UHF stations the filter is just a long tube with female N connectors at each end. You want the filtering to still be effective so don't bypass it. You may have to take the VHF filter enclosure apart to force the antenna relay into the TX position, or add a jumper wire across its contacts, so the transmitter signal always comes out the other end.

To connect an external duplexer, the antenna relay and its cabling need to be replaced with individual chassis-mount jacks and cables, and the relay power needs to be disconnected. Leave the low-pass filter in place between the PA and the duplexer.

For UHF and higher stations, the receiver cable must have a right-angle male SMA connector to mate with the input connector on the right side of the RF Tray. I believe VHF stations need a straight male mini-UHF connector. RG400 coax is used because it's double-shielded and has a stranded (flexible) inner conductor. This cable has to flex when the RF Tray is extended. The other end has to terminate in a female N connector. You may have problems finding such a connector that works with RG400 coax. If so, install a female-to-female N bulkhead adapter in the station and terminate the receiver cable with a male N connector.

The transmit cable just has to go between the output of the low-pass filter and a female N connector on the side of the station. On UHF stations, the output of the low-pass filter is a female N connector, so that end of your cable must be a male N connector. You could use RG214 or RG400 coax. The other end has to terminate in a female N connector. Use a male N connector and a female-to-female N bulkhead adapter if necessary.

If your UHF station has the internal filter/duplexer, you might as well try to use it. If not, get a good pass/reject duplexer with 4-6 sections. There may or may not be room inside the MSF5000 cabinet for it; if not, you might consider mounting it to the rear of the cabinet like I did on my short station. Pull the top cover off, pull the metal cabinet off, mount some shelf or L-brackets to the rear of the cabinet, reinstall the cabinet and top cover, and mount the duplexer to the brackets. Alternately, you can mount the brackets and duplexer to the top cover.

Interfacing Options:

There are several connectors available for interfacing external repeater controllers. There's an entire section on interfacing on the MSF and PURC Index Page and there are nearly a dozen such articles. At a minimum you should read this one as it describes all the signals on all the connectors. There are also articles that summarize where you can find common signals required for most repeater controllers, for the analog and digital stations.

Making It FCC-Legal:

The internal controller of the analog station is preset to identify every 15 minutes and can't be changed by station programming. This would violate FCC rules Part 97.119, which say (in part):

(a) Each amateur station, except a space station or telecommand station, must transmit its assigned call sign on its transmitting channel at the end of each communication, and at least every 10 minutes during a communication, for the purpose of clearly making the source of the transmissions from the station known to those receiving the transmissions. No station may transmit unidentified communications or signals, or transmit as the station call sign, any call sign not authorized to the station.

They improved things for the digital stations. The speed, tone frequency, and interval timing CAN be specified through RSS, so the internal controller will be satisfactory for identification in amateur repeater use. The CW ID is "polite" in that it will not identify if the repeater is in use. This means that a long-winded transmission could result in the interval exceeding 10 minutes. I'd suggest you set the station interval to 8 minutes. Also you should know that Motorola repeaters usually identify without PL/DPL present on the transmitted signal. If you lengthen the repeater hang time to 10-12 seconds, the CW ID will be transmitted with PL/DPL due to the hang time. Most of the RSS settings necessary for a repeater are detailed here

The repeater must be able to be shut down in the event of improper use or operation, or if an FCC agent tells you to do so. Most repeater controllers use Dual-Tone Multi-Frequency (DTMF or Touch-Tone) signalling for this purpose by monitoring the repeater input for control codes. Other methods such as phone lines, the Internet, or a separate control receiver are also acceptable.

A long time ago (1980s and earlier), any repeater could be controlled over the air but only if the control frequency was 220 MHz or higher, which implied a separate receiver just for control. That restriction has been removed, so you can control any MSF5000 amateur repeater over the air, using methods described above. If you plan on using just the internal controller, you still need a way to turn the repeater on and off when necessary. This can be done with a separate DTMF decoder; this article shows you one way to do it. You can also connect such a device to the wire line connector and program the "External PTT Input" (J2 pin 12) to enable/disable the transmitter. Details about how to program this pin can be found in the "Programming Tricks" section of this article.

Protecting The Station:

There's a Metric threaded stud on the side of the station. Connect that to the building ground system with some #4 stranded wire or copper strap. Use a lightning arrestor of some sort, such as AlphaDelta or Polyphaser. Make sure it has connectors appropriate for the frequency and power; I prefer N male and N female. Each company makes products for various bands; get one that will do the job for your repeater. Ground this to the same point that the station ground goes to. Ideally, the antenna coax will have its own lightning arrestor at the point where it enters the building, but not every site will be set up that way.

The MSF5000 power supply uses a ferro-resonant self-regulating transformer that is very forgiving to surges and changes in voltage. Due to the power these stations draw from the AC line, you would need a commercial surge protector. The little ones that you plug into the wall or exist in some outlet strips just won't do the job.

These stations are heavy. Most of the weight is at the top, in the power supply and power amplifier. The station should be installed on a level surface. If possible, try to put it against a wall and add a strap to make sure it stays vertical. This strap will also serve as a deterrent against anyone moving the station.

The switches and knobs that protrude from the control tray are fragile. There's not much clearance between them and the inside of the front door and most parts are No Longer Available. Don't lay the station down on its front or push in on the front door.

Make sure there's a printed copy of the FCC license bearing the repeater's call sign posted on the station or in its immediate viscinity. This should also contain emergency contact information, including a phone number, incase there's a disaster at the site or your equipment is causing interference.

Powering The Station:

Some VHF and UHF stations come with a battery-charging or battery-reverting power supply. These require one or two automotive-style lead-acid batteries and appropriate cables. The station will have two, three, or four Anderson PowerPole connectors on the side for this purpose. VHF stations running more than 25 watts need 28V and 14V power sources, hence two batteries. All other stations run on just 14V, hence one battery. The power supplies in these stations will work better if batteries are attached, but you don't need them in most cases. Without the batteries, when the transmitter is keyed, the voltage will drop by 1-2 volts but will slowly recover. The output power control circuit will adjust for the lower voltage. This article describes how the two batteries are wired on the VHF stations.

These stations draw a lot of power from the AC line. For this reason, you probably don't want to run one on a UPS, because you'd need a large unit capable of 1400 VA for most stations. The power supply is bullet-proof and will survive most AC line problems, but the price you pay for that resiliency is poor efficiency.

For the same reason, expect your electric bill to increase when you install an MSF5000. If you're running it at home, you will see an increase in usage and you'll have to pay for it. If your site offers free electricity, thank the radio gods. If not, be prepared for the increase.

Miscellaneous Items:

A lot of documentation for these stations can be found on the MSF and PURC Index Page in the Manual Library section. There's not much for the VHF stations, but both the analog and digital UHF stations are well-covered. Once Motorola came out with the digital stations, they reduced the contents of the manuals and only provided full schematics for the Control Tray and most of the RF Tray. The power supplies were moved to a separate manual and several pieces have been scanned and uploaded. The RF power amplifiers are essentially non-user-serviceable because the modules are No Longer Available from Motorola and they stopped detailing the parts and schematics.

The power supply, power amplifier, internal UHF filter/duplexer, and most of the RF Tray on an analog station are identical to those used on a digital station and can be swapped if necessary. The control tray is totally different, as is the interconnect board under the RF Tray. This article describes how you can install a digital control tray in an analog station.

The internal filter/duplexer on the UHF stations is actually two separate bandpass filters that serve to reduce the out-of-band emissions from the RF Power Amplifier. The three-section (input) filter is installed between the Intermediate Power Amplifier (IPA) output in the RF Tray and the RF Power Amplifier (PA) input at the top of the station. The four-section (output) filter is installed between the RF PA output and the antenna connector. These filters are tuned using a method similar to tuning the receiver front end, where you peak the first coil then dip the remaining ones. The amount of loss in these filters is critical. The system can tolerate only about 0.5dB per section (1.5dB for the input filter, 2.0dB for the output filter). If there's too much loss, the power control circuit in the station will indicate a fault, either through the "PA LOW" LED or a displayed error code on the control tray, or beep over the air.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.


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This article was conceived Sept 12 2014.

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.