Another bandswitch consideration is heating. RF has skin effect
which concentrates current on the surface, thereby increasing ESR.
As a result, a switch that will safely carry 20a at 60Hz can probably
carry 5a safely at 28MHz. Heath apparently realized this and
compensated for it by paralleling two switches and forced air cooling
them. Congrats to the SB-220s designers for getting it right.
end
On Jul 2, 2006, at 2:22 AM, Frank Goenninger wrote:
> Tom,
>
> Am 30.06.2006 um 16:17 schrieb Tom W8JI:
>
>> Measured voltages breakdown of sample switches:
>>
>> Centralab JV-9000 series single pole
>>
>> contact to rotor 8.5kV
>> contact to contact 6 kV
>> rotor to shaft 7.5kV
>>
>> Progressively shorting Centralab:
>>
>> contact to rotor 9.5kV
>> contact to contact 7kV
>> rotor to shaft 4.4kV
>>
>> RSC Model 80
>>
>> contact to rotor 8.5 kV
>> contact to contact 10kV
>> rotor to shaft 5.5kV
>>
>> The most troublesome breakdown voltage in an amplifier is contact
>> to rotor breakdown. That's always the highest voltage on any band.
>> The lowest circuit voltage is rotor to shaft. Maximum contact-to-
>> contact is generally around half the value of contact-to-rotor
>> voltage.
>>
>> 73 Tom
>
> Thanks for providing measurement data. Comparing for example to
> information from Multi-Tech Industries
> (as found on http://www.multi-tech-industries.com/ - thanks, Will !)
> I seem to need at least a model 90 switch ...
>
> As indicated in another post there isn't enough data for making
> choices/recommendations for selecting a particular switch. Now, of
> course, my question is what that info might be you'd base a decision
> for a band switch on?
>
> Thx es 73 de Frank DG1SBG
>
>
>
>
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>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
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