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Re: initial reflections on AO-40 24GHz

I am certainly not a 24GHz expert but have a few thoughts, probably more
along Antonio's line (i.e., trial balloons)...

Kc2hax@aol.com wrote:
> Hi Folks,
> I visited again Michael's OH2AUE amazing web-site (tnx Michael) and heard the
> K band signals from AO-40, wow!!!!
> Next and as part of my 24GHz endeavour I went trough my microwave books
> (basically those from ARRL and RSGB) and start digesting info on the topic.
> Also visited some other repected sites in the net (e.g.. W1GHZ and others).
> Based on this preliminary review of information below are my initial
> reflections on AO-40 24GHz. I am writing this because I would like to share
> them with you, so you can challenge, agree or disagree and most important
> contribute with info and your knowledge and suggestions on how to walk the
> path from 2.4 to 24.
> 1. 24GHz is going to be a real challenge for those of us that are microwave
> illiterate (I guess a bunch of us here at the bb). BTW, I am refering to
> 24GHz narrowband (SSB, CW) rquired for AO-40 vs wide band FM (WBFM). Yes, I
> know we have been doing 2.4 GHz Rx for a while and that technically speaking
> this is microwaves, but from X band up things are very different (that's why
> I consider myself illiterate).

Yep.  Someplace where an entire wavelength is just 1/2" means
trial-and-error is going to be a lot of error.  Even my trusy 8410B
network analyzer won't make 24GHz :-(

> 2. At this point I really don't know how though the learning curve is from
> 2.4 to 24 without stopping at X and WBFM. Theory is not that though, but form
> the practical point of view it does not seem easy to me (even going the way
> as per #4 below).  I was expecting to cut my teeth on the high freq microwave
> bands with X band on AO-40 and move from there to K, but it seems it may not
> be the case. It also seems to me that X band would be easier, more fun (and
> cheaper) than K mainly because of the availability of a variety of equipment
> from different sources (surplus included). The later takes me to point #3
> 3. There is not much 24GHz gear out there (consumer's worst enemy, no
> choice). I have not been able to identify sources of equipment other than
> Khune (DB6NT), and wish we had some other options, do we?

Not too much.  There are some older 23GHz common-carrier microwave
radios out there that might be found surplus.  Those would make fine LOs
with a simple diode mixer.  
A few companies are starting to make semi-affordable 23GHz low-noise
transistors too, for LNAs.

> 4. Yes, you could do almost one stop shop (willing to spend some real money
> 1K3 DM in EU, $xxxx in US) and get a beautiful state-of-the-art DB6NT preamp,
> mixer, LO, etc... another stop (and toll) to get a 24GHz band pass filter,
> horn and antenna and assemble all together. However, I wonder how much fun
> and learning is in there (am I wrong?). Please do not misunderstand me,
> probably this would be my ultimate goal but would like to walk the path if
> possible (I really love junk ;-)). As an example of this I had much more fun
> modifying and improving my TSI AIDC 3733 D/C (now a great performer, tnx to
> Bob) than installing my SSB UEK2000 in the antenna mast.

Yeah, at least you can get on the air, but I can't afford that myself.

> 5. Even having and willing to spend the money, some items may be difficult to
> very difficult to get (e.g. RHCP, a WG band pass filter, etc)

Those don't strike me as too bad.  There is a 23GHz dual-mode feed horn
in one of the UHF/Microwave manuals made of copper plumbing fittings. 
WG filters I think are straightforward to make, but what do you measure
them with?

> 6. All the previous makes 24GHz a very attractive proposal

Boy, the S/N ratios just look marvy with a 2' dish.  Besides the
coolness of saying you're mode UK.  Hmm...sounds geographic.

> 7. We could discuss this also in Atlanta, would be very nice to have
> somethign like a working breakfast (don't see much space in the program right
> now) in which some 24GHz experts would enlight the illiterate crowd.
> Best 73 de antonio, kc2hax/ea4le
> <A HREF="http://www.qsl.net/kc2hax";>http://www.qsl.net/kc2hax</A>
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