Indeed!
Most eme'rs encounter this issue some point in their operation.
I started out on 144-MHz with only 100w on CW. Then began use of
digital in 2003. But it was not until I started running above 800w
in 2011 that I began to see preamp failure. I like my preamps to not
see RF over 0 dBm (1mw) so that implies the need for 61.8 dB
isolation if running 1500w. Initially I was using a coax relay with
only 45-dB isolation. So I upgraded to better relays (spec >
80-dB). But there are two other paths for RF to reach the
preamp: 1) thru the dc power leads (solved by using RG-58 for my
power leads), 2) poor shielding in coax jumper from relay to preamp
(solved by using double-shielded RG-142).
I also use a sequencer for controlling relay and amp transfer to
transmit (to avoid hot-switching the relay).
These are probably good arguments for using the internal preamp in a
K3S or PR6 at the K3. Internal TR switching protects them.
73, Ed
but the 6M antenna on which I would use it is within 10 ft of two
antennas with which I run legal limit, and I have concerns that it would
survive up there. :) My compromise is 7/8-in hard line for those
antennas, which minimizes the loss, and thus the advantage of a
mast-mounted preamp.
73, Jim K9YC
73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
dubus...@gmail.com
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