Even for 6M moonbounce, there is rarely a need for a mast mounted
preamp. The sky temperature is higher than the noise figure of any
commercial preamp than one could justify spending, even when elevated and
in a quiet, rural location. Some will disagree with this. Now, if you
have excessive feedline loss, mast mounting may be advantageous, but most
people living in residential areas are external noise limited, so an
in-shack preamp is fine. I have worked about 25 stations on 6m EME (none
with the 5K yet).
ICE makes a BCB HP filter that handles 200w and is around $35, so put that
in your TX line and use the RX loop for 6m or possibly put the BCB filter
after the 6m preamp. My setup has the BCB filter in the HF transmit line
and a 200w 6m BPF in the 6M TX line and soon a 3kw BPF on the output of the
8877.
At 02:15 PM 7/27/2009 -0700, Jim Barber wrote:
If we were talking 432 or even 144 I would agree completely, but is there
any real advantage to going mast-mounted at 50? I don't have a problem
with it, but a QRO-capable mast-mounted preamp and T/R sequencer is not
just a little expensive these days.
--jim
Tim Ellison wrote:
Consider using a mast mounted preamp for 6 assuming you have a dedicated
antenna for 6m and not using a preamp in the RX loop. It is always
better to do the pre-amplification at the antenna to improve the S/N ratio.
-Tim
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Jim Barber
Sent: Monday, July 27, 2009 5:00 PM
To: 'FLEX USERS'
Subject: [Flexradio] 5000A - BCB filter and 6M preamp in combo?
For my uses (and until the 2M goodies come along) a BCB-blocking highpass
filter and a 6M preamp are about the only things the 5000A really needs
added to the front end. The receiver is otherwise truly shiny.
In order to address both needs without manual gadget-switching, it seems
to me you could go about it one of two ways:
(1) Put the BCB-block highpass in the main feedline and an unswitched 6M
preamp in the RX1 loop. This has the advantage of being simple, but the
disadvantage/expense of requiring the BCB filter to be able to handle
transmit power.
(2) Put the BCB-block highpass and a *switched* 6M preamp in the RX1
loop. (single box?) Advantage being cheaper/smaller components in the BCB
filter, disadvantages being the expense/complexity of bypass relays in
the preamp stage and the requirement to switch the relay power off/on
when changing bands HF-6M.
Opinions on which would be "better", or perhaps other alternatives?
Thanks,
--jim
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