AS weird background noise?

bwigg · Post by **bwigg** » Tue Jan 24, 2006 11:43 am

I have two AS I's and one AS III. One AS I and the AS III have a weird motorboating background noise on weak analog signals that sound sorta sounds like a beat note between two signals. It appears to be some type of CPU noise from the VOCON board. I swapped VOCONS wih the quiet radio. When terminated into my service monitor the signal is clean right into the noise. It only does it when the antenna is attached. I have ruled out any local source of noise. It does it no matter what the location. I cleaned and tightened the shields and greatly reduced the noise on one unit. But it is still there. The one AS I is dead quiet on the same freqs. Has anyone experienced anything like this?

motorola_otaku · Post by **motorola_otaku** » Tue Jan 24, 2006 3:11 pm

I've got a R-split radio that does that towards the top end, which annoys the bejesus out of me since its primary use is on low-power low-range backyard GMRS repeaters. It also seems to be a bit desensed there too, but checks out fine on the service monitor (.15 - .20 mV squelch break).

It won't make it go away, but you can mitigate it some by bumping down your squelch threshold and setting the unmute type to Standard.

bwigg · Post by **bwigg** » Thu Jan 26, 2006 9:02 am

Problem solved! I found if I squeezed the radio hard enough the noise would go away. After several days of looking for this problem, I found that if the gold front speaker/display board made contact with the chassis at the top of the radio the noise would completely disappear! When the case is installed there is a tiny gap preventing the shield from touching the main chassis. I “rigged” a little finger from a piece of finger stock to allow the front shield to contact the chassis. It is like I have new radio now. Sensitivity has improved dramatically by eliminating the annoying background noise which was killing my weak signal reception.

motorola_otaku · Post by **motorola_otaku** » Wed Feb 08, 2006 10:24 am

Well, unfortunately, that didn't do it for me. But get this: I can use it with a public safety mic with no problems. When I move the mic close to the radio itself, the noise appears; a few centimeters away, it disappears.

I'm thinking this is an external shielding problem and that a new frame, back shield, and (possibly) front panel should fix it. Thoughts? Also, this is a factory-built radio.

bwigg · Post by **bwigg** » Fri Feb 10, 2006 8:43 am

Sounds like RF is getting into the radio somehow. I would make sure all the sheilds are clean and making good connection. Also check that stupid little gold clip on the external antenna port connector. It wedges up against the chassis for a gnd. I find mine falling out all the time. My programming cable picks up the ground through this Ext RF connector. If this clip comes loose it removes the gnd from the connector and my radio will not program. It may also cause you problems if you use a public safety speaker mic with a external antenna.

motorola_otaku · Post by **motorola_otaku** » Fri Feb 10, 2006 12:46 pm

bwigg wrote:Also check that stupid little gold clip on the external antenna port connector. ...It may also cause you problems if you use a public safety speaker mic with a external antenna.

See, that's the thing. It works better with a public safety mic than with the internal antenna. So at least that's not the problem.

Oh well, guess I'll just gor for it and be a $100 or so guinea pig.