Topband: PREAMP/PRESELECTOR

[Bill and Liz]

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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