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Pop On Tx Of Older Radios

HARDROCK

HARDROCK

Active Member
Mar 22, 2011
173
42
38
There is a fix for the pop in ex-speaker on transmit , for example the ss 3900 and alot of
the older connex radios. :)
 

Possible that you are hearing the RF impulse that the speaker that is picking up stray RF from the transmitter. The speaker wire is the most likely suspect, I would add an RF choke or ferrite 'bead'. You can also use a toroid or split ferrite choke. Just wind it around the toroid or split ferrite.

73 mechanic
 
That POP! is likely the switching of the speaker from the audio amp. The speaker amp is used as a modulator amp when you transmit. Maybe try an electrolytic capacitor on the + speaker lead. + side to radio and - side to the speaker + connection. Try anything from 10 uF to 470 uF. Value is not that critical.
 
Captain Kilowatt said:
That POP! is likely the switching of the speaker from the audio amp. The speaker amp is used as a modulator amp when you transmit. Maybe try an electrolytic capacitor on the + speaker lead. + side to radio and - side to the speaker + connection. Try anything from 10 uF to 470 uF. Value is not that critical.
Click to expand...
 
I tried that it did nothing. It is the audio ic causing the issue. I don't fully understand,
the audio ic is on all the time correct?
 
Yeah the chip is on all the time but the input and output is switched from a speaker amp to a modulator amp. Something that is being switched must be causing it either audio or DC control. If I can find the time I will look at the schematic. Don't hold your breath however. I'm on my last couple days of vacation and got called back to work tomorrow for overtime. Oh yay. :mad:
 
Captain Kilowatt said:
Yeah the chip is on all the time but the input and output is switched from a speaker amp to a modulator amp. Something that is being switched must be causing it either audio or DC control. If I can find the time I will look at the schematic. Don't hold your breath however. I'm on my last couple days of vacation and got called back to work tomorrow for overtime. Oh yay. :mad:
Click to expand...
 
Thanks , the issue has been solved. I did not know if i could post the fix, because of advertisement. Do you know ?
 
The audio ic was replaced and audio circuit reworked. I am awaiting the return of
the radio. radioshopsupply romona ca, Chip done the work, reason i posted was to
let others know.... what the cb crowd accepts to be normal is actually abnormal, i
have read other forums where stated, they all pop on transmit it's normal. That is
not true. Eample my ts-50 when keyed up it's dead air!! No annoying pop lol!!!
Thanks for all the replies. 73
 
When you have time. Look at the schematic and let me know
what you come up with. The module fixed the pop, but you lose
audio quality with the module on recieve. Thanks 73.
 
The problem is fixed. r&r communications modified the switching transistor circuit. Finally NO pop on tx or rx. Thanks
 
Three things can cause the pop you hear.

It can be a bad/leaky bypass capacitor to ground on the TX/RX switching transistor, the transistor itself is getting saturated with some stray RF, or the transistor has a bias issue (too high) and it's not "turning off" quick enough. Any one of those three or a combination of those can cause the issue you have. Glad you got it solved. :)


~Cheers~
 

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