On Sat, 10 Apr 1999 02:37:57 -0700 Rich Measures <measures@vc.net>
writes:
>
>
>
>>
>>SNIPPED
>>
>>>>Simple I believe. The voltage is not an issue in the SB-220 but the
>>>>current is. I have examined almost 200 bandswitches and amps that
>>>have
>>>>been run hard on 10/11M show a loss of contact tension.
>>>
>>>Ä So it is the loss of contact tension that indirectly causes the
>>>resistance of the suppressor resistors to substantially increase
>>>without
>>>showing an outward sign of resistor overheating?
>>
>>
>>On 10M which comes first, the cart or the horse?
>>
>>It was agreed by most, (sorry if you were not invited,) that many
>common
>>suppressors do run hot on 10M and extended use will result in an
>increase
>>in R. This in itself does not guarantee the wrath of the parasite
>god.
>
>>>
>>>>This soon leads to overheating and eventual failure.
>>>
>>>Ä only open bandswitch contacts arced.
>>
>>Yeah sure. You already stated that the arcs are on 10M. In the SB-220
>>case that means there are NO open contacts.
>>
>? I did not state that the arcs occurred during 10m operation. I
>stated
>that the arcs occurred at the open 10m contacts. The photo of the
>toasted bandswitch in the QST article "Parasitics Revisited" Sep.,
>Oct./1990) shows a bandswitch that was damaged during 40m and 80m
>operation, when the 10m, 15m and 20m contacts were open. In the
>photograph, the 10m contacts are those with the most damage. The 20m
>contacts are the least damaged.
>- later
Was this one of the mailed in switches? How can you assume the prior
condx of any contact before the final failure?
There are many reasons for switch failures but parasitics are not one of
them IMO. According to yourself and others the path to ground for VHF
energy is thru C-Tune and not thru the tank coil/switch.
I hope we are not going to go all thru this debate again. Its getting to
be a bore.
73 Carl KM1H
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