Batboard

A 3 year old UHF CDM1550/GM360 I recently programmed was almost 1KHz off frequency. Reception of very weak signals has improved now it is more or less on-frequency.

I wonder if anybody has any views on whether its worth attempting to improve RX sensitivity by realigning the Front End filters? Does Motorola usually set up each radio carefully in the factory or do they just use default values and hope for the best!!!

Thanks

The radios are tuned at the factory... that said, any radio should be tuned on the bench before placing it in service. They should also be PMed every 12-18 months.

Though I agree completely with the statement of 12 to 18 month PM's, the front end alignment is one of those softpot settings that in my experience RARELY and I mean RARELY ever changes. I've checked radio front ends that hadn't seen a service monitor in nearly 10 years and did not get any noticable changes, we're talking 5 points up or down to get a .01 RSSI change. (mostly refering to HT1000 UHF/VHF units here) I would not guess that CDM's would be much different.

Just a note here on the SoftPot settings in Jedi radios. You can have them scrambled by cloning or putting in another radio's 'codeplug'.

tvsjr wrote:...They should also be PMed every 12-18 months.

PMed?

preventive maintenance

SRN1322B pretty much says it all.

Wow!!!! Motorola says approx. allowable frequency error of:

- UHF (20/25KHz): 1.850KHz
- UHF (12.5KHz): 1.375 KHz
- 800MHz: 2.125KHz

If one radio is +1.850KHz and the other is -1.850KHz then represents big error of 3.75KHz!!!

Moto also says that the "Ref Osc is only adjustment that requires periodic attention"

I could only find SRN1322 NOT SRN1322"B" - so maybe there has been some changes!!

My gut feel is that you want to be within +/- 400Hz for optimal FM weak signal working

I'm guessing we've switched from front end alignment to ref osc alignment.

The tollerances they gave you were system wide totals. This I can speak from personal field experience. The astro series radio will not function properly (in trunking) with a system wide freq error of more than 2 kHz (radio plus repeater). However straight analog radios can handle system wide freq error of nearly 3k and still trunk. Again this is from personal experience as I had a system running nearly 2.5k off freq and the only radio not function was an XTL and the occasional analog radio low by .75khz. With all that you can see where the field specs are half that .9 for UHF WB .7 for UHF NB and 1.0 for 800 and technically .8 for 900 which isn't shown. And as we all know this isn't where you lose quality this is where you begin to lose functionality so keeping your radios within 500 hz plus or minus is always the best way to go.