General Dynamics R2590 Sinad calibration question

[sparktastic]

Hi guys,

I'm really struggling to find any information on my R2590.
I'm located in Australia, which doesn't help of course since the local Motorola solutions who used to service this unit, no longer support it and there are no other 'local' service agents.

Anyway, I'm wondering if there is a R2590 guru here that can help with a query regarding the unit's FM Sinad meter.

Basically, I have checked the generate output level, tone deviation etc and all is within spec, however, when I do a Rx Sinad test on any radio, the sensitivity/Sinad readings are about 2dB low compared to other known Service monitors.

For example, the receiver sensitivity of a radio tested on a known/calibrated HP service monitor may be -120dBm (@ 12dB sinad), but on the R2590, using the same DUT, the receiver sensitivity will be about -118dBm (@ 12dB Sinad).

As I mentioned, I have checked the generate output level of the R2590 and it is the same as the other Service monitors, but the Sinad meter seems off.

Does anyone know if there is a way to calibrate the Sinad meter in the R2590?

I know these Service Monitors are a little 'funky' in their operation but as far as I am concerned, the dodgy Sinad meter is the only major problem I have with the unit.

Any other calibration info would be fantastic. I presume there is a power up function that puts the unit into calibration mode, but I can't find it.

Thanks,
Rick

[Wowbagger]

One thing to check is what audio filters are being applied to the measurement. Normally, the specified test conditions for SINAD in FM voice work are that a C-Weighted filter should be applied to the audio before measuring the SINAD. If your set up is not applying that filter, but is instead applying something like a 300hz-3kHz bandpass, you would see worse measurements due to more high frequency hiss being accounted for in the measurement.

[MSS-Dave]

http://freedomcte.com/service-support/

This company picked up the GD line of monitors several months ago. You could call or e-mail to Doyle Wofford there for tech type questions. Had a 2590 years ago and worked with him on a calibration issue when he was with General Dynamics, he moved with the product line to Freedom. I see they list Motorola Solutions as a service partner in Burwood, Victoria as well.

Dave

[sparktastic]

Thanks guys.

Actually, when I looked closer at the specs on the R2950, they are pretty poor.
For example, the RF generate output level accuracy is only specified to+-4dB and the Sinad meter accuracy specified to +-1dB.
So, while the R2590 Service monitor is giving relatively inaccurate Sinad readings, it appears that it may well still be operating within the original spec
I didn't realize this aspect of the R2590 design, otherwise I probably wouldn't have purchased it.

Anyway, it makes the +-1.5dB generate output level accuracy on my (5 year older) HP 8920a, look rather good now..