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Old 03-02-2014, 08:48 AM
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CO Hunter CO Hunter is offline
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Join Date: May 2010
Location: Colorado Springs
Posts: 106
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The weather has kept me from playing around this weekend. I posted the UHF SWR behavior in the FT857 yahoo group and got this response.

"Dear Sir: I repaired a radio with same similar symptoms. Get a Service Manual. Follow the RF trace from the VHF/UHF finals to two PIN Diodes leading out to the low pass filter section and from there going out to the antenna SO-239. In my case it was the first pin diode, which you can check from the ((((((circuit trace to the diode))))))) and then the diode itself. Mine was not soldered from the factory, but worked for some time before the symptoms appeared. When I touched it with the DVM probe the pin diode went flying over my head. It's a 25 watt pin diode, I replaced it with a 50 watt pin diode. Your SWR intermittent is caused by the Foward/Reflected sensor is seeing the loss of connection through the LPF, and antenna conn. Good Luck"

I have the circuit diagrams. This looks like it may be a bit above what I am able to do. I may open up the case and take a peak to see if I can identify the area of the PA circuit involved.
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