But my feedline I use is a run of Cat 5 ethernet cable, with one pair carrying the signal and the
other 3 pairs sharing the +V and 0V load. So I need to reconfigure the amplifier's T6 output
transformer for separate power feed, and balanced 100 ohm coming out.
It's actually fairly simple, and can be accomplished with a few modifications. First, break the connection
between T6 and C20, then connect your power line to C6, Q6, etc. to complete the supply connection. Done.
Looking at the output side of T6, break all of the shown connections. The upper terminal of the upper
winding is your + output, and the lower end of the lower winding is your - output. Connect the lower end of
the upper winging and the upper end of the lower winding to ground. Done.
The collectors of Q3 and Q4 will now see load impedances of 200 ohms instead of the original 400 ohms, so
the power gain will be reduced by 6dB.
Thanks Chris!
Hopefully the 6dB reduction won't be too much of a penalty. I would have to go to a different design for T6 to get the gain back?
Not easily and it wouldn't be worth the effort, but you could add an additional 3:2 autotransformer after it that would raise the collector load impedances to 450 ohms, which is reasonably close and would actually raise the gain by about 1.0dB. I don't have a drawing set for that readily available as I've never had to describe one, but it's fairly simple.
Chris Trask
N7ZWY / WDX3HLB
Senior Member IEEE
