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Author Topic: Motorola Service Monitor  (Read 31682 times)

N0PLB

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Motorola Service Monitor
« on: May 12, 2011, 08:36:29 AM »

I know that a lot of you rely on your service monitor to keep your repeater up and running at it's optimum, I would like to know what types and brands are being used and if anyone has a service manual for a Motorola model R-2400a, I know that the 2200a and 2400a are included in the same operators manual but not for sure about the service manual.

Tell us your hints and tricks that you have found for duplexer alignment, site noise assessment, etc.
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N5NPO

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RE: Motorola Service Monitor
« Reply #1 on: May 12, 2011, 06:07:21 PM »

I am not familiar with that Motorola SM. My company has a Motorola R2550 and I think it is awesome. Easy to operate and not overly burdened with a lot of menues. Only drawback is it does not have a tracking generator.
The mainstay SM at our company is the IFR COM-120B. Ours have the tracking generator option and they work well. Our newest two SM's are Aeroflex 3920's. Awsome machines, but the learning curve is a bit steep. Our units have tracking generators, spectrum analyzers and work on P25 and Kenwood Nexedge modes as well as EDACS and conventional modes.
As far as tuning duplexers, I get the best results using an Anritsu Sitemaster 312D to tune each can for maximum return loss at pass frequency and then use a tracking generator to adjust the notch for the deepest notch at the desired reject frequency. You must tune the pass frequency first and then leave it alone. Moving the pass will affect the notch, but not vise versa.
Site interference is a horse of another color... There is an online intermod calculator on Commscope's website. A spectrum analyzer is of great value.
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AD4U

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RE: Motorola Service Monitor
« Reply #2 on: May 13, 2011, 06:29:28 AM »

I own 3 repeaters (six meters, two meters, and 440) and I maintain three more for our club.  They are all GE Mastr II's, so that simplifies matters a bit.  The duplexers are a hodge podge of different brands. Cel Wave. Wacom, Tx Rx, Sinclair, Motorola etc.

I use a Motorola 1200 service monitor which is around 30 years old and lacks a lot of features that some of the newer ones have.  I also have a HP 141T spectrum analyzer and tracking generator, which is a necessity when maintaining repeater transmitters.

While not the best way to tune duplexers, I use the Motorola 1200, a couple of 6dB "pads", and a Sinadder.  On the receive pass adjustment I tune for maximum sinad on an ICOM R7000 receiver.  I do the same on the transmit pass adjustment followed up by slight adjusting for maximum RF power output with low power.  On the rejects I tune for minimum sinad on the R7000.  This has always worked for me and none of the repeaters has any de-sense.  I can "look" at the pass - reject on the spectrum analyzer.

Of course if you have access to a good network analyzer, that is the way to go to tune duplexers.  I just don't have $50,000 to buy one.

Dick  AD4U
« Last Edit: May 15, 2011, 06:24:23 AM by AD4U »
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KM3W

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RE: Motorola Service Monitor
« Reply #3 on: May 13, 2011, 10:02:12 PM »

Hi all,
I also own and maintain 5 repeaters. A converted Mastr II on 220, a backup maggiore on 444, a Bridgecom commercial repeater on 444. a GE Mastr Pro on 448, and a Bridgecom on GMRS (462). As for service monitors....I have 2. Both Motorolas....one is a 2001D/HS, and a R2200B. Of the two, the 2001D is my favorite because of its large screen and more features. With all of this discussion ..I was wondering...who does your calibration? I have Tessco about 100 miles from here....and Cardinal in Chicago....2 questions.....what SHOULD be the average cost to do the job? I was given a price of $700 a piece from Tessco..... Cardinal is half that, but I have to ship it. Any Ideas or suggestions? Anyone had dealing with either?

de KM3W

shield1751@me.com
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N5NPO

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RE: Motorola Service Monitor
« Reply #4 on: May 14, 2011, 05:16:05 AM »

Service monitor calibration service:

My company used to use EML out of Tennessee. We have now decided to just send our Service monitors to Aeroflex (formerly IFR) for repairs and calibrations. Most of our SM's are Aeroflex/IFR anyway. The Motorola will probably go to EML still, unless it needs repairs, then it will go to Motorola.
73
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N0PLB

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RE: Motorola Service Monitor
« Reply #5 on: May 14, 2011, 09:15:12 AM »

Wow! I didn't realize I was going to get so much good information!
Does anyone know if the Motorola ever offered a tracking generator as an option for the R-2200a or R-2400a?
Please forgive me if I ask something that you consider I should know, but as a beginner with service monitors and it being so hard to find information about anything Motorola, if I don't ask I'll never know even if it is in the form of being politely being told how stupid I am.
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AD4U

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RE: Motorola Service Monitor
« Reply #6 on: May 15, 2011, 06:35:10 AM »

I bought an extremely accurate external time base for my Motorola 1200 service monitor.  Its long term accuracy is something like 10 to the minus 8 or minus 9.  I have found that when checking the output frequency of my 1200 against other more elaborate instruments, it is "right on". 

For example when feeding a 900 MHz signal from the 1200 into a multi-thousand dollar recently NBS calibrated HP frequency counter, my 1200 is consistantly within about 4 Hz of the counter read-out.  This is good enough for my work.  For typical HAM work, I don't think a periodic NBS calibration is necessary unless you have reason to think yours is way off.

Dick  AD4U
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K4JJL

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RE: Motorola Service Monitor
« Reply #7 on: May 26, 2011, 05:42:00 AM »

I've had a couple monitors over the years.  First was a Cushman CE5000.  Heavy!!!  Not fun to tote to the sites, but it has a tracking generator that's the easiest to use of all my monitors.  No menus to go through to make quick changes.  I can usually align a preselector or a duplexer in under 15 minutes with it.  It's 100% analog, too, which means that the changes you make on the filter are seen instantaneously on the CRT.  No digitizing delays.

Next I got was a Motorola R2600 at a bargain basement price of $100.  It was a nice unit, but didn't have a tracking generator.  The upgrade from Tessco was $800, so I decided to pick up an HP 8920 for less money instead.  I ended up giving the R2600 to a really close friend who was still using Cushman CE4s.

The HP 8920 is a great unit.  The 60w dummy load is a pain to deal with when it comes to tuning 100w repeaters.  I need to find a dummy load with a 30db power sampler built in.  Tracking generator is great.  I also like the fact that you can easily switch between measurement units (db vs V, rms vs pk-pk, uV vs dbm, etc.)  If you're running the same tests on multiple radios, you can program the tests right into the unit to step through.

When I scrape some cash together, I need to get some of the option boards for the HP.  I've seen the encode/decode boards on ebay for around $80.

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KA5IPF

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RE: Motorola Service Monitor
« Reply #8 on: May 26, 2011, 03:36:56 PM »

I started with a Cushman CE31B in '81 (still have it). In '96 I bought a HP 8920A, fully loaded. Over the years I have used a few IFR's and Motorolas but nothing compares to the HP. It's on about 8-10 hrs a day 5 days a week and has been for 15 years. The only service was when I messed up, otherwise no problems at all. I'm not real happy with the digitized spectrum analyzer but can live with it. For testing radios I use the North American FM Test package. It runs thru a series of user selectable tests with the operator changing parameters on the radio as directed, even prints out a test sheet.

For SSB work it's great, need a 2-tone generator with precise levels and frequencies for tx testing or setting carrier oscillators, got it. Signal generator with calibrated output, check, does 10dB SNN testing automatically, I'm still finding things it will do. Tracking generator to align those front ends, cavities, etc.

The high stability timebase is calibrated in software, no xtal tweaking. I check it about every 6 months against a Z3801 satellite rcvr. Takes less than 10 minutes.

I recently picked up a HP 8921A for cheap that is an 8920 in cell site test clothing. That almost guarantees the 8920 won't break since a backup is ready.

I wouldn't have anything else, YMMV

Clif
KA5IPF
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