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RE: 24Ghz Gunns



Hello James

I'm by no means an expert but Gunn assemblies I believe are OK for wideband
FM operations like ATV but for narrowband operation the oscillators are way
too out of control. Even if this were not the case the sensitivity of these
devices is probably rather lacking. And I'm afraid AO-40 is weak signal
judging from some of the audio on the web on the K band downlink.

The frequency stability is apparently quite an issue at these frequencies
with narrow band stuff, so the cheaper ATV equipment which uses lower
stability DRO oscillators would probably not be good enough either.

You can build a solution off the shelf from DB6NT parts except for the
antenna and waveguide filter. You don't have to use a filter, but you'll
suffer noise from the unused IF image if you don't.
http://www.db6nt.com/oscar.html

This is serious stuff which will send tidal waves into your credit card
account... I've not been brave enough myself yet.

I get the impression that the pioneers on AO-40 K band live and breath this
stuff in their day jobs, and so have access to a plethora of machining
equipment and 5 figure sum test equipment etc. But then that's what I
thought about 2.4GHz until I pulled my finger out.

Hopefully I'll be proved wrong and one of us on the BB will come up with a
solution made out of elastic bands and copper pipe: after all I have seen
waveguide transitions made from standard plumbing copper pipe. Although I'll
have to get my machining skills improved.

73 Howard G6LVB

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