Mag One BPR40 UHF RX audio howl

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Mag One BPR40 UHF RX audio howl

Post by OldDawg »

I got 2 of these things here I need to fix. The radios DO NOT HOWL, unless the boards are seated in the housings. They do howl with/without external spkr/mic's attached.
Speakers are not the issue. Changed them out. 455 filters are not the issue. Changed them out too.

Anyone had any success in resolving this problem? I have a pile of boards in the bonepile I can scavenge parts from....
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Re: Mag One BPR40 UHF RX audio howl

Post by train_radio_guy »

Sounds like a microphonics. When I worked on GE-Ericsson radio equipment in the mid-1990's we had the problem with a number of radios. Usually poor grounding was the cause, or faulty shielding. I'd start by double-checking any chassis screws, and be sure they're properly tightened. Then move to shielding. And technical information, such as a service manual would be helpful at this point, if it's available.
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Re: Mag One BPR40 UHF RX audio howl

Post by Satelite »

Call me nutz whatever but i had that same howling issue with motorola P100 uhf portables years back and no matter what i did it howled until i changed the housing out.
Cant say for exactness why this solved the issue other than in my opinion the new case and or chassis whatever you want to call it had a sprayed on coating that likely shielded something.
If your willing id try swapping out the bds into a non howling chassis case and see if its still an issue.
I even had the impression that the original howling cases in my situation eventually broke down on sheilding or even took on a reflection of rf rather than sheild or absorb the rf as a explanation trying to explain it but ill be honest i really dont know why ect other than change the case chassis ect howl went away.
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Re: Mag One BPR40 UHF RX audio howl

Post by arlojanis »

I have had the same problem with UHF Mag Ones. Did not find the problem. Never had the problem with VHF radios.
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