First, I have never seen in single case in all the hundreds
of relays I have tested at high power RF where the contact
RF behavior is an issue. Sometimes the contact support,
which can be steel or an alloy with high resistance or
exaggerated skin effect is an issue with heating, very often
the flexible wire leads are an issue with heating, but I've
yet to see a contact heat issue if the contact is OK at low
frequency and the same current. I have tested many relays!!
On your switch, my feeling is you are going through far too
many relays and the connection lengths will be too long. I
understand what you are doing to make it safe, but I'm
afraid with so many relays and so much connection length
isolation and SWR will not be so good.
You could compensate for this with capacitors (like the 47pF
you show) and with selection of layout and materials, but
large numbers of large relays in the path makes isolation
and SWR more difficult above a few MHz. If you find that not
a problem, then all is well.
Watch your groundplane! It carries as much current as the
center conductors do, and is just as responsible for
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