Topband: Help for Preamplifier

Ralph Matheny mathenyr at
Thu Mar 23 10:38:38 EST 2006

The preamp shown in ON4UN's book (latest ed.) from the work of IK4AUY is
a very good one.  A word of caution, however--there is a discrepency
between the bias resistor values from the ON4UN book and the article by
IK4AUY.  I believe the values in the original article are correct.  The
preamp is quiet and hard to overload--and in my experience terminates
filters properly.

Another comment.  Make sure you NEED a preamp.  If everything is well
matched and you have controlled any leakage into the system by decoupling,
grounding, etc. you may find that you actually have enough signal without
any gain.  I used a preamp here for a long time, but when I went to work
on shield RF pickup/re-radiation problems and the like I turned the preamp
off and now I don't seem to miss it.  Of course if you have miles of
feedline and a low-gain receiver your case may be different.

Ralph Matheny
207 Gibbons Place
Marietta Ohio  45750

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