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How to reduce uBITX output power?

vick.perry@...
 

Hi, 

I have had success with the WSPR beacon mode using Dr. Lee's uBITX firmware. On each WSPR band, I matched my antenna for low SWR as best as I could. On some bands, the finals get VERY HOT so I would kill power to the uBITX hopefully before I destroyed the finals. I do realize that digital transmission modes are high duty cycle loads. 

In an attempt to reduce output the uBITX RF power, I turned RV1 clockwise 1/8 turn to reduce output power on the finals - that helped prevent overheating. 

Is adjusting RV1 the best way to reduce output power with a stock uBITX build?

Regards,

Vick KG7UNJ

Tom, wb6b
 

I have a small mains powered fan. Placing that near the heatsinks keeps them cool. Right now I just turn it on when needed. I'l use a 12v fan when I finally put the uBITX in a case. Rather than add the extra complexity of temperature control, I'll just hook the fan to the 12v from the uBITX transmit relay contact.

Tom, wb6b

Jerry Gaffke
 

Adjusting RV1 is the best way to reduce power.
You might also go to a bigger heatsink someday, but note that the IRF510 tabs are at 12 volts
so be careful you don't ground them.  Tom's fan is also a good idea.
You do not want the IRF510's getting so hot you can't hold your finger on them.


On Tue, May 29, 2018 at 08:51 pm, <vick.perry@...> wrote:
Is adjusting RV1 the best way to reduce output power with a stock uBITX build?