*Proceedings of the Institute of Radio Engineers*,
September, 1935.
"PARASITES AND INSTABILITY IN RADIO TRANSMITTERS"
by G. W. FYLER, General Electric Company, Schenectady, New York.
" ... Methods of locating and eliminating parasitic circuits are
discussed.
"A PARASITIC in radio work is any spurious oscillation taking place in a
vacuum tube circuit other than the norrnal oscillation for which the
circuit is designed. ... ... "
... ... ...
- "Conclusions:
In the elimination of parasites from a transmitter, the circuits should
be kept as simple as possible to prevent complex resonance conditions.
Radio !requency choke coils and shunt-feed circuits should be kept at a
minimum. Wide band neutralization circuits are desirable. The grids of
vacuum tubes should be effectively by-passed capacitively to the cathode
through a capacity and inductance added next to the plates of the tubes
to eliminate shortwave (VHF) parasites. If necessary, the plate or grid
parasitic circuits should be damped with resistance. ... ... "
--------
In the 1926 and 1927 Radio Amateurs Handbook, F. E. Handy recommended the
use of resistance wire to reduce parasitic oscillations. In Oct., 1988,
an article about the use of resistance wire to reduce parasites apeared
in *QST*. In 1996, tests were performed with a HP Z analyzer which
indicated that, all other things being equal, VHF suppressors made from
resistance wire provide an improvement of roughly 40% compared to
copper-wire suppressors.
. Where's the beef?
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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