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Wednesday 26 September 2012

M1KTA version of ARRL 50W PA

I have a Dx trip I am about to go on and I have been asked if I can try LF and the ARRL 50WPA challange looks like one option as it will do 160/80 and 40m.

Drive will be from KX3.

I had a Microwave Modules 25W 2m pa doing nothing...

So time to remove the guts...

 Interesting 12v relays I might find a use for them another time... The main transistor is junk so it will no longer work but I'll save the board in case I want if for later.

Cut a piece of FR4 and slid into where the original used to be and cut two 'panels' for TO220 IRFZ24N transistors. I have a dual IRF510 PA that might do in case this one doesn't work.

This is the input side... I used a BN43-202 and not the FT37-43 as originally spec'ed as I had seen from PIC-A-STAR that the VSWR in input was better wih the binocular core, I note that in the original Donald W6JL used one anyway!

Input stage:

I am building mine Manahatten style with pads (cut from a sheet with harbour freight punch) all the parts except the PA transistors and the output toroid were all from the 'junk box'. I had ordered a few of the transistors and the BN43-3312 a while ago.

Output stage added:

I used a couple 1000pF poly caps temporary and I put them into the RG58 out sleave off cut.

I will replace with a single 2000pF (c2n2) cap.

The space top left will be for an RF sense and QSK relay. See N6BM Miniboots PA for an idea of that.

The random extra manhatten pads in the centre I'll remove.

I will add a fan on the top of the heatsink.

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