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Old March 23rd 06, 06:16 AM posted to rec.radio.amateur.antenna
K7ITM
 
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Default SMT Inductor(RF choke) with SRF about 3GHz

So, why is it that you need "tens of microhenries"?? Having built
(after doing some redesign on it) a doppler-scanning antenna before,
I'm having a hard time seeing why you would need that sort of
inductance in your antenna switch. I guess you better use some low
capacitance PIN diodes, and resonate them with inductances to reflect a
high impedance back to the "off" antennas...and I can see a need for RF
chokes that represent a couple hundred ohms reactance at 2.4GHz, but
that's only a few nanohenries, not tens of microhenries.

You should be able to have one diode forward biased and the rest
reverse biased by the remainder of your logic voltage level...if you
want more (why?), use high voltage open collector gates as drivers, or
just four discrete transistors.

Layout: make it very symmetrical, so each antenna behaves the same
way. Standard microstrip techniques should work fine. If you're not
used to working with this stuff, I highly recommend enlisting help from
someone with experience, at least to give you occasional guidance.
In-person help will be much more useful than what you get on r.r.a.a.

Cheers,
Tom