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 Post subject: MOTOROLA R1200AX SERVICE MONITOR
PostPosted: Oct Mon 23, 2006 6:27 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 63
Location: Western Australia
Got one of these to check out , but seemingly no info from web searches. eg: Edebris/Bama etc. for service or operators manuals
Three modules in situ are Deviation Readout, Audio Synthesizor, Hi Gain BroadBand Mixer
The RF generator and attenuator check out fine and I can feed in an external synthesized RF CW signal at 10dBm to the Mixer module and get a zero error'' readout on the analog meter 10MHz below the input frequency

But if I feed an AM or FM modulated signal as above the Deviation meter doesnt indicate. (the pointer bounces about a bit uncorrelated to input , either noise or a fault?)

First does anyone know of a downloadable operators instruction manual or service manual for this and , second, from more knowledgeable members than me, is the 10MHz offset ime getting correct for this unit?
I take it to check out a transmitter you use an in line attenuator or attach a whip antenna to the mixer input BNC ?
Any advice on how to check it out properly appreciated

This is a 'love job' for my next door neighbour so ime doing all this for free. (Except I get to use his 60 ft tower!) No dough available to buy a manual so any advice gratefully received.
By the way this unit (S/N 05056) was made by Systron Donner for Motorola according to the rear plate and has an SD type number of
SLN6393A -6, But no joy on a search for this either

Best Rgds all
JBEE


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 Post subject:
PostPosted: Oct Mon 23, 2006 7:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 31178
Location: Maryland 20709, USA
Hi JBEE,

I last used one of these about 25 years ago, so the following is from somewhat faded memories :D

The R1200 should have a built-in dummy load, good for ??100?? watts, so you can key a transmitter up to that power level directly into the test set. This is through the main input connector at the lower right. But don't rely on this without independent corroboration.

There's also a preselector/tuner plug-in which is used to pick up signals off the air or from a hand-held radio. I don't know what its max power level is but likely much lower than the broadband input.

Common usage would be to key the transmitter and whistle into the microphone. A properly calibrated whistle (:eek:) should give you peak deviation. The regulatory limit here in the US is ±5 kHz, but your standards may be different.

There's no frequency offset that I ever encountered. I didn't try to access the inner workings since I was using it to check two-way radios. All of the operation in that environment was based on setting the actual operating frequency on the dials.

This is a nice unit. The SLN number is from Motorola, not Systron Donner. SD did not make any comparable product under their own name that I know of. I believe this was a Motorola design.

_________________
73 de Leigh W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


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PostPosted: Oct Tue 24, 2006 6:47 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3372
Location: Monterey California USA
The R-1200AX is the basic 1200 with the option of a high stability timebase (the "X.") The modules have been added later.

There is no internal load in this model. It is designed to monitor off-the-air signals or to be used with a pick-off enroute to an external dummy load or antenna.

I don't have the manual anymore, but this is how it works to measure deviation and frequency:

1) Dial up the known carrier frequency
2) Press the RECEIVE button
3) Press 1.5, 5 or 15 KHz to select range (FREQ ERROR)
4) Connect whip antenna or cable from pick-off to broadband mixer
5) Place wide/narrow switch in "wide" unless there's interference, in which case use "narrow."
6) Read frequency error on ERROR KHZ meter
7) Set deviation meter range as desired
8 ) Read deviation on meter when transmitter is being modulated

Unfortunately these are 30+ year old instruments which have usually seen a hard life. They are worth little on today's market, as they have no value to commercial shops, thus intensive labor to get one running has to be considered a lost cause at some point.

I have had some where the electrolytics in the deviation meter module were totally dried out and open circuit. Other electrolytics in the unit, same story. Tantalum dip capacitors can be shorted, they are becoming notorious for this.

The manual, as I recall, is rather huge and would be a life's work for someone to scan and put on the internet. Operating the thing should be a pretty intuitive process.

For generating a signal, use the CW position generally as that is locked to the TCXO. The red "Leveled" lamp should be lit normally. If it is out, it means the output has either become unstable or the overload protect circuit has tripped (hence the reset button.)

The FM Cal knob sets the frequency when the generator is in the modulated FM mode. It should be zeroed with the zero center meter. The stability while in the FM modulated mode is rather poor, it's just for testing receivers and not frequency setting. Leave it in CW normally.


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