Grounding problem most likely. Mine will squeal when I use the built in speaker as well. I use an external speaker and wind the excess wire around the speaker and zip-tie it. No more squeal.
OK a couple questions. I know you said when you key the mic but does that mean when you talk or when you just key the mic? If it is the latter then take the radio out of the place or if you can disconnect the external speaker. If it still squeals, then it is a mic issue. With that, turn that talkback crap off or all the way down. If it doesn't, then you may have a leaky rf connection or bad coax somewhere and the speaker wiring is picking up the rf, making it squeal. Your solution at this time is three things. 1- You can order ferrite toroid or large beads from ebay and put them on the line which may stop the problem - I say may because I am not there to assess the problem first hand. What this will do is stop the RF from reaching the speaker and causing the problem. 2 - replace the coax, make sure that the radio and antenna has a good ground. 3 - use an external speaker that isn't part of the truck.
Radio is out of the box, Not tuned coax is a couple of years old. reception is awesome, very clear and can hear for miles. I've got an old external I'll try tomorrow Edit: bought this radio on ebay as used, So I guess its possible someone may have opened up the radio. It worked great when installed in the mack, same coax and ant. and mic
Are there some sound holes underneath mount? May just want to use the built in radio speaker, Ive used mine before it sounds pretty good. You are absolutely right about the receive it is excellent, as good or better than an older Cobra 148 gtlf I own, and my audio is great too, I havnt had a tune up done to it but I bought it off of Amazon for $105.00 and I wonder if the shop that supplied it did a peak and tune because out of box it had a carrier of 3.5 to 4 watts and a pep swing to 15 watts.
No sound holes. When installed in the mack didnt use an external speaker. Well I have a few things to look at now
Apparently it was the talkback it was set at 12, Took it down to zero and no feedback. Rf gains at 5. Where do you set the mic gain at Or do I get radio check for clarity
If the radios limiter hadnt been removed or other golden screwdriver mods and with a good noise canceling mic or stock mic , which is also noise canceling, should be able to set it on maximum 4 level, the only time I have ever lowered it to level 2 was when I tried an Astatic D104 power mic which is not noise canceling.
I have a RF Limited 2018 Extreme Echo mic and I can see the benefit of having talkback to set the level of echo( which I chose to not use, not a big fan of echo) and I can see having talkback on an export radio to set echo level but other than that I dont see its benefit. Obviously most drivers dont use it to set echo level because they have way too much. Your probably thinking why did I buy a echo mic if I am not a fan of echo, well without using the echo and dont crank the modulation up too much they are really a good sounding mic and they also have a noise canceling switch on them to eliminate feedback.
It still makes no sense, why would you want to listen to your "before RF" audio when some of the distortion for signal quality happens after the final RF amp stage. It would be better to have a real way to monitor it, which is on air listening. I looked at a few circuits this morning and it seems they designed it only as a selling feature without thinking how it could be effective.
