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To: <>
From: "k7fm" <>
Reply-to: k7fm <>
Date: Sat, 3 Jun 2006 17:44:24 -0700
List-post: <>
> Rich said:
> "I  do not agree.   Rotating the bandswitch in a properly tuned 220
> results in a reduction in peak-V across the Tune-C and the
> bandswitch.  in my opinion, SB-220 bandswitches typically arc from
> the intermittent parasite at 110mHZ.  The arc is the result of 110MHz
> energy not being able to reach the load through the low-pass tank and
> running amok."
> I reapired a SB-220 a few years ago that suffered bandswitch failure when 
> the owner did exactly that - turned the bandswitch instead of one of the 
> tuning controls.  I mentioned it at the time and Rich questioned my 
> veracity.  I was not there and only can convey what my friend told me and 
> I observed.
> It seems to be human nature to pass the causes of damage to one's own ham 
> gear as the fault of the design of the gear or the fault of someone else 
> rather than an error of the operator, so I cannot believe that a friend 
> would admit the he made a stupid mistake rather than blaming the equipment 
> design - if he had the opportunity.  Now, he could have lied to me because 
> he thought it was better to make a mistake in tuning the rig than to admit 
> he purchased an amplifier that was not adequately protected from 
> parasitics - or to admit that he was operating an SB-220 without the Rich 
> Measures protection circuit - but I am more inclined to think that his 
> statement that the damage to the bandswitch occurred at the exact moment 
> that he turned the bandswitch instead of the tuning control was true.
> My observation when I received the amplifier was that the bandswitch was 
> indeed damaged.
> I also have an observation on the statement by Rich about "Rotating the 
> bandswitch in a properly tuned 220".  There is an assumption that may not 
> be valid in his statement.  If the operator turns the bandswitch by 
> accident instead of the tuning control, that is an indication that the 
> amplifier is not properly tuned.  If it was properly tuned, the operator 
> would not be tuning it.  So, the basic assumption of Rich's statement is 
> based upon a fact which is not likely true.
> Colin  K7FM

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