>
>
>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.
>
The article was not directed at any particular tribe. The IRE article
was recently received by yours truly and I thought some folks might be
interested. It would have been nice to have had the article during the
grate parasite debate.
>Reminds me of the horsecrap I got from a few "experts" about the use of
>very slightly inductive 5W MOX resistors
It wasn't equine feculence. I bought a few of those resistors and they
were pretty inductive.
> as I use in parasitic suppresor
>circuits on 6M along with MuMetal as the inductor.
Mu metal is more resistive than copper, however, there are much more
resistive alloys.
>.......
>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.
>
Interesting, Carl. Tin/lead certainly has more R than gold.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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