Re: Power output decreases as a function of frequency? #bitx40


John McFadden <johnamcf@...>
 

Raj,

Could you suggest a method for bypassing L1-L3? I'm not sure how I would do that with any temporary change, any approach I can think of would be permanent and then attempting to reverse the damage later.

And where is the output filter on the board?

Something is definitely off center, I set the Raduino to transmit out of band and the power tails off in a rather symmetrical pattern centered on 7000khz, with another attachment showing the output power vs frequency.

Thanks!

John

On 12/29/2017 11:20 PM, Raj vu2zap wrote:
Could be something with L1-3. Temporarily bypass the filter and try another test.
I have one board with the filter centered a bit and gives less power higher up the band
but we work only till 7.2MHz.

It could be the output filter also.

Raj


At 30-12-2017, you wrote:
Bottom line up front:

I am having a problem with my Bitx40 where the power output decreases as I increase my frequency across the 40m band.


I completed all of Allard's 1.27.3 mods, plus RX/TX lights, and the spurious emissions capacitor, with it transmitting through a SWR meter into a 50W/3.5ghz dummy load. Power is from a variable power supply set to 12.0V, which includes powering the PA.

I'm receiving the following readings from the SWR's forward power gauge and the power supply's current meter as a function of the tuned frequency when using my straight key for ~1 second:

Frequency, SWR meter forward power, power supply current;

7005khz, 4.5W, 1.15A;

7050, 3.8, 1.06;

7100, 3.0, 0.98;

7150, 2.5, 0.91;

7195, 1.9, 0.82;

7250, 1.3, 0.72;

Join BITX20@groups.io to automatically receive all group messages.