>
>
>
>On Thu, 8 Apr 1999 11:13:44 -0700 Rich Measures <measures@vc.net> writes:
>>
>ALL SNIPPED
>
>>>>
>>>> This is somewhat of the principle behind a load pull test. You
>>either
>>>> short out or open circuit the output of an amp and then rotate it
>>around
>>>> the Smith chart (via Ctune). Also, the tank inductor generally
>>provides
>>>> a large enough reactive impedance to VHF energy that it likely
>>doesn't
>>>> matter wether you have a load on or not.
>>
>>Ä amen. In parasite-arced bandswitches, damage occurs primarily on
>>the 10m and 15m taps. .
>
>
>Completely subjective and unproven Rich.
>
? the photographs lie?
>
>Another option which I subscribe to is Peters/Ians version when it comes
>to parasitics.
>
>In a real amp that is 100% stable to start with, the switch failures are
>primarily due to the mfg trying to save a few $$ and using a poor
>initial choice .
? The TL-922 and SB-220 bandswitches have a withstanding potential of a
bit under 6000v at sea level. The peak RF potential in both amplifiers
is around 2900v. (see arced bandswitch photos on my Web site and in
"Parasitics Revisited", Sept./Oct. 1990 *QST*)
? If such bandswitch arcing is not vhf-related, why is it common to see
>100% increases in R-supp after bandswitch arcing?
>Before the doubters wind up in a snit I suggest that they take a real
>look at the specs of the commonly used switches and try to understand
>exactly what they are spending money on.
>
? Better yet, use a high-potential tester and evaluate the bandswitches
yourself.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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