Update 27-Feb-2020: Tnx to PA0VAJ Jan we discovered a huge fault in the diagram. I guess I need to solder wires to other places. I'm curious if you as smart reader will discover this huge fault. Hint: transformer. Of course, more to follow...
Original idea from the MFJ-989D to S-match conversion by PA0FRI. First tests are not promising.
The problem is room...
The coil needs to be isolated from "earth". It is, but it is probabely too close to the alu box floor causing a kind of capacitive loading. I'm also not shure the earth connection through the core of the S-match transformer is a wise choice. I will make some mods and test again.
For those that are interested:
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| MFJ-948 conversion to S-match scehematic diagram |
Note: You cannot switch the transformer independable to 2 antenna's. You connect coax to the PL connector (coax 2) or open line to the coil or the capacitor(s). Not both at the same time! Switch is also used to connect second capacitor in parallel for low bands.
3 comments:
Hope you use ft240 core, instead T68 /t300-2 types, : https://www.dg0sa.de/smatch.pdf or : http://home.scarlet.be/on9cvd/S-match.htm
73s Peter PG3N
I use T200-2 like PA0FRI. That's not the problem...73, Bas
However I agree changing the transformer core could be a nice upgrade...73, Bas
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