Re: PA transistor Heatsinking of a uBITX #ubitx

Jerry Gaffke
 

That looks pretty good!
Was it otherwise a stock rig, so these are the only changes?

Jerry


On Sat, Jun 9, 2018 at 03:21 pm, Ralph Mowery wrote:
I made several modifications as designed by others.  I am not an engineer,but can do the 'mechanical work'.
 
I installed 330 pf capacitors across r87/r88, feedback reisitors r261/r261 to 820 ohms, the output transformer was changed ot a BN43-202 core with 2 turns primary and 3 turns secondary.  I think I should have used a 33 pf across the primary of the new transformer,but used a 150 pf.
That was with the change of the output transistors.
 
Here is my power out with the drive pot cut back some.
 
Freq   output watts
 
3.7 MHz  11.9
5.33         10.5
7.2           11
10.1         10
14.2          8
18.1         10.1
21              6.8
24.89         8.3
28.2           8.7
 
Not totally flat, but except for the dip at 21 mhz it is not too bad.
That was made with an IFR 1200s service monitor and a 13.8 volt 50 amp  Astron supply.

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