On Sat, 19 Sep 98 09:33:34 -0800 Rich Measures <measures@vc.net> writes:
>
>*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...
Are you still harping on this subject Rich? I havent noticed any
naysayers on the AMPs reflector since I reattached 5 weeks ago.
Reminds me of the horsecrap I got from a few "experts" about the use of
very slightly inductive 5W MOX resistors as I use in parasitic suppresor
circuits on 6M along with MuMetal as the inductor.
Many experts split their time with their head in the sand and their
thumbs up their ass ... some are known to do both at once.
BTW, I work on Millimeter Wave stuff daily in my real job and you better
believe we even have parasitics at 40 GHz ! The cure is often a very
small application of solder on a gold plated trace at the input or output
of one of the TX stage amplifiers. It has almost no effect ( about .2dB)
at the desired TX frequencies but certainly shuts down all those little
spikes on the HP-8565E Spectrum Analyzer.
73 Carl KM1H
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