R2001a Service Monitor question

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kc9mmm

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Have a question regarding the deviation display in Power Monitor mode on the R2001a service monitor. The total deviation would be the sum of the positive and negative deviations amounts, correct? The manual doesn't really explain this question, I would assume that to be the case, but then we all know what happens when you assume things.

Reason that I ask is because the other day I was checking a Astro Spectra and I was surprised at how much I had to turn down the deviation softpots to get it into spec. After adjusting things all the on air reports of it said the audio sounded just fine, both on analog and P25.

I believe the service monitor to be reading the deviation correctly as if I generate a signal with a known width of deviation it reads the value correctly.

Ed
 

RFI-EMI-GUY

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If you are looking at a bar graph it should have - at the left end and + at the right end. I Don't think it should read the sum, or 10 KHz, unless you are mentally adding the integers to left and right.

FM "wide band" deviation in land mobile radio is "typically" +/- 5.0 KHz. The radio manual may have you set for something less or give a tolerance.

What you should see on the deviation oscilloscope is +5 and -5 KHz. The modulation bar graph should follow the scope. If the filter options let you go down to DC on the scope to measure deviation, you can calibrate the scope by inserting a dead carrier, lets say 446.000 MHz and then tuning the R2001 to 446.005 and you should see the scope biased to -5 graticule. Do same tuning the R2001 to 445.995 and you should see the scope biased to +5 graticule. This may sound backward, but it is correct.

I have not used an R2001 for decades so I don't know the screen or filter settings. I use an HP8920B which is more flexible, but more difficult to use than an R2001.
 
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kc9mmm

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I see my error now, the help page in Tuner didn't specify the +/- 2.83 Khz to set the transmit deviation limit to, and I hadn't really heard of it actually being +/- 5.0 khz as wideband, only 5.0 khz. Surprised that I had that good of a signal report with only have of the deviation that I should have had.
 

RFI-EMI-GUY

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The 2.83 sounds like the P25 deviation. Be sure you set that mode properly or you will have high TX BER.
 
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