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MTR2000 Interfacing

By Eric Lemmon WB6FLY
HTML'd by Mike Morris WA6ILQ
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A note from Mike WA6ILQ:
Prices quoted below are early 2008 prices, and Eric's employer has an NSO account (National Service Organization, available to Motorola service shops and large end-users). Prices availalable to any individual reader of this page will most likely be higher. On top of that, Motorola adjusts their prices quarterly, so a few months from now the prices listed will probably be different.

To: Repeater-Builder
From: Eric Lemmon WB6FLY

Now that I have some hands-on experience with MTR2000 repeaters, I can 
pass along some suggestions.

1. The MTR2000 Depot Service Manual 6881096E35 ($184.45) contains the 
   admonition that any signal to the auxiliary audio input (pin A17) 
   MUST be AC-coupled through a 100 uF electrolytic capacitor. Failure 
   to have this capacitor in line will upset the bias on op-amp U4509, 
   which is DC-coupled to the backplane connector. Some controllers 
   have DC-coupled or transformer outputs, and may not work properly 
   without this capacitor. In fact, you'd be wise to use a similar 
   capacitor (with the positive end pointing towards the station) for 
   any and all audio signals to and from the station.

2. Rather than mess with mismatched connectors from Digi-Key or Mouser,
   simply buy the "System Connector Kit" from Motorola, P/N 3083908X02,
   for $55.46. This kit includes the proper connector body, along with 
   30 wires already terminated with male pins.

3. The current RSS for the MTR2000 is RVN4148P, version R03.03.02, at 
   $278.00, and is not backward-compatible.

4. The essential accessories needed to program and test the MTR2000
   station are:
   a. Programming cable 3082056X02, $50 (DE-9F on one end, 8-wire
      modular on the other end)
   b. Amplified speaker HSN1000, $97.75. The manual can be found on the 
      main MTR2000 index page. Note that the HSN1000A/B speakers have 
      been replaced by the HSN1006A. A manual for this model is also
      available on the main MTR2000 index page.
   c. Speaker cable 0185180U01, $15.51. I drew a wiring diagram that is 
      available on the main MTR2000 index page.
   d. Microphone GMN6147B, $59.93. This is a three-button microphone that 
      uses the additional buttons to adjust the volume and select the mode 
      (channel). Yes, the MTR is a multi-channel base station or repeater. 
      Routine testing cannot be performed without the microphone plugged 
      in. The info needed to use this microphone, scanned from the MTR2000 
      Service Manual, is available on the main MTR2000 index page. The 
      GMN6147B has been replaced with the GMMN4063B mike, which has been
      described as a "Fist" mike, and it is intrinsically safe. Its cost 
      is $61.20.

5. When installed in a rack, the MTR2000 should be mounted on standoff
   brackets to keep the units center of gravity centered. Motorola offers 
   some nifty brackets designed just for the job: part number 0784384T03 
   at $66.73 for the pair.

6. This Is Important! 
   Note that the high-power (100 watt) VHF station comes in two splits: 
   132-154 MHz and 150-174 MHz, and the higher split can NOT be made to 
   operate in the 2m band. This restriction only applies to the 100 watt 
   power amplifier; all other components of the station, along with the 
   30 watt and 40 watt power amplifier, cover 132-174 MHz. I have read a 
   number of "horror stories" about clueless amateurs who bought used 
   commercial MTR2000 repeaters with 100 watt PAs, and then discovered 
   that they can't program them below 150 MHz. Caveat Emptor! 

   How do you tell if the repeater has the 100 watt PA? It's easy: only 
   the 100 watt PA has a fan on each side, one for the PA and one for 
   the high-capacity power supply. By the way, the MTR does not use the 
   traditional Motorola numbering scheme (like C73RCB3106BT) to indicate 
   the band and power level. You have to decode a bunch of cryptic Field 
   Replaceable Unit ("FRU") numbers in order to identify exactly what you 
   really have, and these labels are not always visible! An article with 
   a list of the FRUs is available on the main MTR2000 index page.

7. Buyers of a new MTR2000 can save several hundred dollars by deleting 
   the wireline (tone control) interface card and the AC power supply. 
   However, be aware that the 100 watt PA operates on 28 VDC, while all 
   other PAs run on 14 VDC.

8. All MTR2000 stations have only one two-circuit PowerPole connector 
   for the backup battery. That's true whether the station has an AC 
   power supply or a DC power supply. The only difference is that the 
   high-power stations expect 28 VDC to be applied to that connector, 
   while low-power stations expect 14 VDC. The high-power stations, 
   both AC and DC powered, use 28 VDC for the PA and have an internal 
   14 VDC regulator for running everything else.

73, Eric Lemmon WB6FLY

A note from Mike WA6ILQ:
Several of the larger Motorola base stations, including the MTR2000, use Anderson Power Pole connectors (or the AMP Corp. clone) for the DC backup battery connection. Rather than purchase them at a premium price from Motorola you can get them from Digi-Key (1-800-344-4539) for less:

Please read the "Setting up the MTR2000 for Battery Backup" article, available on the main MTR2000 index page, before you attempt to connect batteries or an external power source to the MTR2000 using the Anderson connectors.

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Original text (the white background) © Copyright 2005 by Eric Lemmon WB6FLY
Hand coded HTML © Copyright 2005 and date of last modification by Mike Morris WA6ILQ

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