Most Beverages don't require a preamp of any type, in my estimation. The
shorter ones may need a bit of a boost but those over 500 ft seem to do
quite nicely on their own most of the time. If you do believe that some
amplification is necessary then 6-10 db is about all that you should
consider using lest you overwhelm your front end and introduce more noise
and garbage.
Now, IF you need a bit of a boost, consider killing two stones with one
bird. If you have a need to eliminate some noise, the MFJ 1025/1026 noise
reducers have a bit of a preamp built in. It is just a few db but it might
suffice.
When I need just a bit of amplification I use the preamp built into my
radios (PRO2 and K3). The preamps in both these radios appear to do a good
job in my application (though I have no real idea what the REAL noise figure
is).
For loops and other RX antennas whose gain is -12db and beyond, an external
10-20db amplifier is desireable and there are a lot of choices out there,
from the simple but effective W7IUV and KD9SV designs ( both of which I have
built and use) to the more "exotic" designs by the likes of W8JI.
I am referring only to amplification above. If you require selectivity in
front of the RX antenna for any reason then that is a completely different
situation and one of the commercially manufactured preamps with tuned input
is desireable.
IMHO anyhow.
Bill VE3CSK
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