Power output decreases as a function of frequency? #bitx40


John McFadden <johnamcf@...>
 

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;

7295, 1.0, 0.66;

A graph of the above is attached.


During RX, the power supply's meter reads 0.14A. When I hold the PTT down, the meter reads 0.34A.

When I did a signal report with a friend in the same town on 7249khz today, he reported he was unable to hear my voice and could barely make out my key from the noise.

Any suggestions on what I should check first?


Thanks!

John

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