24 GHz

24 GHz

Postby w7qq » Thu Feb 01, 2018 6:27 pm

Wooo! It was a great day today!

I've been working on establishing capability on 24 GHz for over a year. It's been a challenge. This started with a fascination with Wide Band FM rigs on 24. The community has a pair of those radios made by Advanced Receiver Research. They use 10 mW gunnplexers and I wasn't very impressed with their performance. I expressed some interest and before I knew it the microwave specialists emerged and started throwing extra equipment my way. That stuff was very nice but I still needed a local oscillator and a pre-amp. The pre-amp required an enclosure integrated with WR-42 waveguide to get the signal into and out of the pre-amp. Thinking I might screw up one enclosure I decided to make two and quickly found I wasn't limited to screwing up just one.....

By that time the 24 GHz bug had bitten because I had made a couple of nice long QSOs on 10 GHz. The idea of elevating the challenge to 24 GHz was settling in. I would have been fine if I had kept it to myself but that just wasn't part of the plan. So fast forward (through the spending money part) and I decided that a 24 GHz station made up of parts connected with semi rigid coax would be easier.

Even that approach required some tedious integration, fabrication and a little bit of testing. So the maiden voyage didn't go well. I made a short distance QSO with K5RHR and another longer one with N0IO. Signal strength was weak and troubleshooting determined that the TR relay, which I thought to be a latching relay was in fact a "momentary on" type relay. So I had built a system with no transmit or receive signal path to the antenna! Sheeesh! After carefully testing insertion loss of all semi rigid coax, and the new TR relay I pronounced the 24 GHz station ready for a second try.

That was today. Mark, N0IO had lent a second 24 GHz station I could use for some performance testing and I began the big event by having lunch with KK6MC Duffey then moved to some station setup and finally some testing. We made solid contacts across a parking lot, then extended the distance to about a mile and later about 9 miles. It was right there where Duffey discovered the IF radio (FT 817nd) on his end was set on split, which explained why we were ratcheting all over the band during previous tests. The final test was an attempt at a QSO from my home QTH in DM75ao to Sandia Crest (DM65sf); about 39 miles. After preparing for a weak CW contact after a difficult "find each other" grope on pointing and freq tuning we were both surprised to point antennas, dial up 24.192 Ghz and we had a nice S9+5 QSO at 39 miles. Duffey said it was like a rag chew on 2 meter FM and I had to agree. Cool! It was a great fun day.

So onward and upward. There are a few nits to improve but I think I'm on 24 GHz finally. I'll be headed to Lake Superior next August during the 10 GHz and up contest. At last count there will be four NM VHF Society members there and we hope to make dozens of contacts on microwave bands!

I'll be presenting this adventure and a more complete story at the New Mexico Tech Fest on February 24th.

73 Bill W7QQ
Posts: 44
Joined: Fri Jan 01, 2016 11:22 am

Re: 24 GHz

Postby K8TE » Sat Feb 10, 2018 2:32 pm

I look forward to attending your presentation Bill!
Posts: 5
Joined: Mon Jan 04, 2016 11:38 am

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