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cobra 29 black chrome rfx75. Hum

wilson04

Member
Nov 29, 2009
31
4
18
I just installed the RFX 75 in a new cobra 29 BC. I followed cbtrick instructions to a T. When I transmit I get a "hum" behind the audio and when the mic gain is up all the way the ANT light comes on (only when I talk). My SWR in the truck is about 1.4 - 1.5. Any help would be appreciated.
 

The SWR was checked with an ext. meter. I have a galaxy 99v that works perfectly in the truck. Could it still be a bad ground or maybe lack of power if other radios perform perfectly? I'm new to playing with radios and I dont have a dummy load yet. The only way I check them is in my semi. I will check the swr pot or remove it. Thank you for your help
 
Did you replace the power cord? the factory power cord on the 29 will not handle the needs of the RFX-75 29...
 
The power cord is 10 or 12 ga. with a dc filter in line. It is all in one, I bought it that way. It was not an splice job. would the filter matter?
 
Yeah, I would think that it should be 10 ga wire.
But I don't think that is the problem that makes the hum. If it were me doing this RFX conversion; I would go carefully over each step from the instructions and re-check everything. I would even do it three times to be sure. I would also reheat all solder connections I made, to be sure that I didn't make a cold solder joint. If that proved to be all done correctly, I would take it to a nearby tech and see if there isn't a fault with the RFX unit.
But that is me...
 
I tried a new power cord and it still had the hum. The hum wasn't constant though. It is always there but will get louder and softer. It doesn't seem to have any rhyme or reason to it. I have also checked and resoldered all the connections. I think my next step is to try it in a different truck and then a tech.
 
ITS A BAD EARTH CREATED BY THE RFX 75 WHICH IS CAUSING THE HUM ON TX KEY UP....................TRY LOCATING THE RFX 75 TO A DIFFERENT LOCATION IN THE RADIO AWAY FROM THE OUTPUTS
 

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