The T/R switch can be a point of concern, as you pointed out. The problem
with a knife switch, however, is after the operator has had too much Corona.
Best solution is to eliminate the T/R switch altogether and use separate
antennas for receive and transmit. Stacked beams are good on the higher
bands, with the taller beam going to the receiver. Then, adjust transmitter
power so the the transmitter and receiver have an equal range.
On the lower bands, if you cannot afford stacked beams, you can use back to
back terminated rhombics. One problem with this arrangement is that your
receiver will have a high rf level from your transmitter. Overload can be
prevented, however, by using a tube rf amplifier and mixer that are immune
from overload. A 4-1000A receiver rf amplifier biased at 436 ma will work
up to +186 dbm. A pair of 4CX5000 tubes running as a balanced mixer seem
to work well. The vfo needs 186 volts of rf.
Colin K7FM
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