What Mike says is true in his case. However it
depends, I think, upon your system and it's
isolation during the TX On cycle. RF can
sometimes sneak around a RX Isolation relay, into
the LNA's input and also into LNA box through the B+ lines.
In my 1296 EME system I'm seeming to have better
luck turning off the preamp during TX. On this
band, there are various techniques and methods of
trying to achieve circular polarization. I
believe that the RX/TX isolation can go to pot if
either port is not terminated in 50 Ohms when
it's not being used. The PA output circuit and
it's coax to the feed will not be good enough.
BTW, G4DDK, who provides V(very)LNA kits and is
an active EME'er, I believe. recommends LNA OFF during transmit.
GL es 73,
At 04:29 PM 6/29/2011, Mike KL6M wrote:
I'll put the 432 feed in for you for this weekend.
My preamp is always on. There are X schools of thought on it (from a lot
of folks who are in to theory and have minimal EXPERIENCE). When I ran my
AMSAT stuff years ago my MGF1302s were blowing like popcorn due to
switching them on and off. I've never turned my LNA off since and have
never blown one.
Mike, KL6M BP51dc http://www.qsl.net/kl6m
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.Â Â Is it better to leave power to the
preamp on, or turn it on/off with the sequencer when switcihng between
If all goes well, I should have 64 elements, 500 watts, and 25 db of
preamp ready to try some eme.
Moon-Net posting and subscription instructions are at
Moon-Net posting and subscription instructions
are at http://www.nlsa.com/nets/moon-net-help.html