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How to reduce uBITX output power?

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?

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

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