PR40—9
TESTING AND ADJUSTMENT
With your preamp installed between antenna and receiver, the only adjustment needed is the
obvious one: peaking L1 for maximum signal strength. This may require more patience than
most of us would think, because the adjustment should be made on a weak signal
transmitting long enough to permit the adjustment. You can adjust L1 by gently spreading or
squeezing the coil turns. Use a non-metallic tool or a small toothpick. This coil does not use
an adjustable coil slug because such coils are not suitable at this frequency due to the small
inductance required. Since this is a low noise preamp, don’t look for an imaginary increase in
noise level or waste time trying to make a strong repeater signal seem stronger!
CAUTION
Under no circumstances should transmitter RF ever be applied to the input or output of this
preamplifier. Even though this sounds like unneeded advice and common-sense knowledge,
we should remember that most of today’s receivers are in transceiver configuration, and that
all it takes is one accidental push of a button out of habit, or an inadvertent bump of a keyer,
to destroy a preamplifier.
