Saber intermittent audio/PL on TX

[mr.syntrx]

Hi

I've got a UHF "T-band" Saber III with intermittent audio and PL on transmit.

When I bump or shake the radio while its transmitting, it will intermittently cut out for about half a second. The display and LED stay solid, so I know the battery is not being interrupted. The service monitor still shows it transmitting at full power but with no modulation during these periods. This occurs in both clear and secure, with and without a secure module fitted.

I've tried reseating the internal modules. Where should I go looking in order to fix the problem? At this stage, I'm thinking something is up with the front shield.

Cheers

[mike m]

I seem to remember a TSB for this problem years ago. There was some type of kit available with shielding material that you placed between the front assy and the RF board.

It had some crappy shielding mesh material on it but as I remember it didn't work very well.

I just checked and I don't have the info anymore but I do have one of the radios with the kit/mods in it and it still does the same thing that you mention plus the tx audio will increase and decrease around 3 dB when bumped around. Never had the time or need to look at it as it is a low split UHF which was given to me.


Mike

[DJP126]

I can think of 4 possibilities for you.
1) Make sure the mic has an insulator over the solder contacts. A piece of electricians tape will work.
2) Make sure the BACK shield isn't shorting out to the main circuit board. Again, electrical tape will work.
3) You could have an intermittent VCO. Try substituting it.
4) U101 might not be making good contact to the circuit board. This would require reheating the device so the solder would reflow to the circuit board.

[mr.syntrx]

I popped open the radio, and found the top screw on the rear shield near the antenna connector was a bit loose. I tightened it right up, and no more trouble.

Thanks guys.

[GlennD]

I highly recommend that you install the REX4421A noise kit. It costs less than $15 and it helps many radios. The older synthesizer modules with the rounded corners usually do not have this problem.

We use both the 440 and 450 range Sabers in our system. We have a SP version of RSS that allows us to use the 458 sabers at 453 Mhz. The 458-490 range synthesizers are much more prone to noisy distorted TX PL. I have no experence with the 512 range Sabers.

[mike m]

Txs for refreshing me on the kit name/number REX4421A. I think I may still have one in a box in my junk pile in the garage.


Mike

[GlennD]

It consists of some insulators and a silver conductive pad. It helps to make the radio one electrically. A few years ago Motorola supplied it free but now it costs.