1600S Dev Adjustment

[Big BOB]

I just purchased an IFR 1600S. Everything seems to work just fine, except the FM deviation scale is about 1 Khz high. I compared this with 2 other service monitors.

Is there an easy adjustment that I could turn the Dev. scale down?

Big BOB

[Wowbagger]

Are you saying the FM deviation METER is reading high, or that the modulators are GENERATING too high a deviation?

Before you go too far on the 1600, you can confirm the deviation by using the function generators and the analyzer, by performing a Bessel null check: set one modulator to 1kHz rate, and a 2.4 kHz deviation. At that setting, the carrier should disappear on the spectrum analyzer - tweak the deviation up or down until you get the deepest null. At that point, you are MATHEMATICALLY guaranteed to have a 2.4 kHz deviation on the modulator. You can then check both the settings of the modulator and the deviation meter.

Also, the 1600 deviation meter can show several settings: (FM positive peak - FM negative peak)/2, FM Positive peak, FM negative peak, or FM RMS - make sure you are comparing apples to apples.

If the deviation meter really is out of cal, you can calibrate it or have the unit calibrated. I don't remember the cal password for the 1600, but update this thread next week and I can chase it down.

If you are going to be doing REAL work with the unit, I'd suggest getting it calibrated properly.

[Big BOB]

I took the Dev. meter out of Auto Range and set my own limits and it seems to be fine now.

Would you still be able to give me the calibration password for the 1600S? It would be nice to have on hand.

Thanks

Big BOB

[Wowbagger]

I took the Dev. meter out of Auto Range and set my own limits and it seems to be fine now.

Would you still be able to give me the calibration password for the 1600S? It would be nice to have on hand.

Thanks

Big BOB

Looks like the answer is "no" - while that cal password is printed in the cal manual, the cal manual is currently only available via purchase.

However, there are several shops that can do a cal on the 1600. If you care enough to get it calibrated, you really should have it calibrated at a NIST traceable shop.

Sorry.