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Author Topic: Preamplifier limitations  (Read 3294 times)
WD4ELG
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Posts: 875




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« Reply #15 on: December 29, 2012, 05:26:32 PM »

Thanks, Steven.  So for lossy antennas (like receive only antennas, there is some benefit).
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G3RZP
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Posts: 4619




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« Reply #16 on: December 30, 2012, 12:17:16 AM »

There MAY be some benefit. When I used a tuned loop (2 turns, 1 metre each side of the square) I used a push pull cathode follower on it. Had to be a tube, since I got 80 volts on tx from the vertical 70 feet away! But no preamp was necessary there.

The K9AY 'EWE' I found very quiet, and that didn't need a pre-amp, either. But you DO need to make sure that if using a separate rx antenna, you don't get enough pick up on it to cause damage, such as blowing the fuse bulb in some Yaesu rigs. A relay slaved to the PTT line drive to the amp is usually good enough if it's fast small one. Maybe even a PIN diode switch, although for 160, you need some 10 microsecond lifetime PINs. I have used 1N4008 for that, but not all makes of 1N4008 will  necessarily have a long reverse recovery time.
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