>
>> I didn't know relays would wipe from normal current flow through them. I
>> thought wiping was strictly a mechanical operation arising from the
>> closing and opening of the contacts. How does it do this from normal
>> current flow?
>
>Different contact materials have different hardness and even
>shapes. High current contacts are harder materials with wider
>contact areas,
? For high-current RF applications, vacuum relays use copper-contacts.
> while low current contacts are softer materials with
>smaller contact areas.
>
>High current contacts rely on a bit of voltage and current flowing to
>"burn away" any film or non-conductive deposits, while low current
>contacts have a softer surface of a material that doesn't
>contaminate as easily. The pressure is also higher in a small area,
>allowing mechanical wiping to have a larger effect.
>
>This is a common problem with high current relays used to switch
>receive lines, and why a few low power "hot switches" will clean up
>a high current relay. Vacuum relays of course avoid these
>problems.
>
>The ideal amplifier open-frame relay would use low current small
>surface area contacts on the receive side, with high current
>contacts on the transmit side.
>
? Open frame relays are not ideal to use in conjunction with modern
radios because the switching times are so slow that hotswitching is
likely.
>
cheers, Tom
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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