Hello Paul, There is another issue to consider for power on/off the preamp. The noise figure and the gain of an amplifier (preamplifier) are not a fixed and a stable values. They vary with temperature. That's why, after switching on an amplifier there will be a time period to stabilize those parameters. In other words, if the LNA is switched off during transmission, each time when it'll be switched on back on the reception sequence, it will experience the same noise and gain deviation! Saying you have a LNA with 20dB gain and Nf = 0.4dB on a stable state (working more than 1 hour). When you switch it on, you'll have about 22dB gain and Nf = 0.6dB (Nf depends also by your matching network!). Usually, the Nf should be less at start-up than on stable state but due to thermal deviation of the matching network components, could be worse. time. 73 de YO3FFF Cristi ________________________________ From: Paul Decker <kg7hf(a)comcast.net> To: moon-net(a)mailman.pe1itr.com Sent: Thu, June 30, 2011 2:07:46 AM Subject: [Moon-net] preamps Hi all, OK, I have a 432 MHz preamp, tx sequenceer, bypass relays, all ready to go for this weekends antenna work. Minor question for the group. Is it better to leave power to the preamp on, or turn it on/off with the sequencer when switcihng between rx/tx? If all goes well, I should have 64 elements, 500 watts, and 25 db of preamp ready to try some eme. thanks, Paul