radio trasmits squeal

[elmerjfudd21]

I have a trc-423 radio I just got. I had one already and tuned it to 9watt dk and decided to pick up a nother. the radio was used but when I got it it would dk almost 1 watt so I tunned it to 3watt installed an onboard amp and now it transmits a squeal. I removed the amp and tried retuning the radio and wile tuning I can tune the squeal out but that also drops my watts to almost none and still with it tuned out I key the mike all is fine till I talk and the squeal drounds out my voice.

any ideas would be awsome! thanks guys

[frogman296]

did you clip the modulation limiter??

[elmerjfudd21]

no I can demodulate to almost nothing aslong as the mic can pick up any input it starts to squeal. also when the amp was hooked up when I would key the mic the amp would trasmit ok with the squeal but the power had to be cut to stop the amp from keying.

[Rick]

Try the radio with on Amp, if it still squeals, check the choke connected to Pin 4 of the mike socket it may look alright but its most like short. Also check the caps around mike socket.

[elmerjfudd21]

thanks for the help guys

I checked the caps on the mic pins thay seamed fine. so I checked the mic it had some channel up and down buttons. I riped them out and rewired the hole mic matching the wiring of my good mic with out the channel buttons and all is good. no more channel selectors on the mic but it works.

amp still will not stop transmiting any ideas on that? it's a new kl 60 onboard. the key curcit I can hear click when I key up but when I let off the mic it keeps going untill I pull the power to it. the amp forces the radio to continue keying aswell. just tryen to push a bit more power I can get 18 miles off my radio and looken for 37 to my wifes work.

thanks again for the help

[frogman296]

onboard amp??? man..those are a disaster waiting to happen...did it some with some sort of "rf shield"??

[RedEye]

Those RM Italy KL60 boards are crap. I have removed them from radios when they come in for repair. TERRIBLE RF around them and like you said, almost every one locks up on TX from poor rf shielding.
Don't do the SSB mod in the directions, it will short and they won't replace it....

They actually only TX about 35~40 watts am anyways, (when they work)much safer to do an EKL mod or put a IRF520 in place of the stock final, you'll actually get better results!

They use a single IRF 520 that they scrape the numbers off of, and NO HEAT SINK!

[timrim]

Sounds like the Amp is self oscillating, If this were an outboard amp, I would suggest using a longer jumper between radio and amp. I see that problem a lot. Inboard amp does not leave much room to lengthen input jumper.

[speedracer6g]

If you are using an onboard linear you will need to sheild the board. If not it will bleed rf all through the board and well you found out what happens. to verify this take the radio apart with this board moved away from the radio. if it quits wich most likely it will that is your problem. I would recoment getting some alluminum flasing or something along those lines and make one or i can sell you one of mine that i make for cheap. mine fit inside the cobra 29 and 25 fine. they are an inch high and the same width and length as the pcn-60 board. I do alot of those boards and they get a bad reputation because you have to put them in right. I rework the output stages to get about 2.5 watts deadkey and swing to 10 this gives me about 15 watts deadkey and 30 watts swing. about 50-60 pep. no modulator cap and resitor crap. I also use rg178 50ohm coax also to tie it into the board. I also install the board on the power buss after the filter in the power supply to help keep alternator noise out of the rf section. You may have to beef up the power filter also.

MIKE