24 GHz Beacon by OK1EM

OK1EM 24 GHZ hamradio beacon for radio amateur microwave

Edvin OK1EM made a beacon for 24GHz band based on DMC oscillator. Here you can read a story translated to English, for more pictures and to see the original article please visit a Maják pro pásmo 24 GHz

24 GHz Beacon

I needed to make a small beacon for the 24 GHz band. As a basis, I used oscillator type DMC – 110368 operating in the range 23.684 – 24.853 GHz. The crystal in it was replaced by 107.358 MHz.

Frequency stability in the original DMC was not optimal. That’s why I made OCXO DF9LN.

The stability has already improved and is satisfactory for my needs. The DMC module is powered from a power supply ( – 5 V and + 8,4 V ). The DMC module itself has a power of about 8 mW. For further amplification only the amplifier from the DMC UP converter is used. This is keyed by a simple keyer bastle made on a pcb with holes programmed with a PIC16F88A. The beacon was permanently keyed during setup. The output power of the beacon is 30 mW.

I was looking for a slot as an antenna. The drawing was provided by Pavel AIY. See his stalker:

I was looking for some information, see some links. I found out that Jirka RA made the SLOT for his lighthouse by hand. He drilled and filed the files. I didn’t want to do it as a bastle, but somehow properly.

I was looking for different companies that deal with sparking or other electrical discharge machining. Most of them were very expensive. I finally chose PeRoz EDM. I supplied them with a WR42 waveguide. Mila UFL drew me a plan, see picture.

The company made it and I’m happy with it. See photos:

Testing the beacon and setting the SLOTU in home conditions:

First I wanted to set the SLOT using my measuring instruments. Their results did not satisfy me. Next, I tried the initial setting and listening of the beacon in the laboratory, when the signal passes through two walls.

The receiving part of the transverter is on a mast about 150 m away from the house. The IF signal is routed to the lab. The height difference of the laboratory is 30 m in relation to the mast. In the lab, the signal was heard but the S meter did not move. I have another beacon there with less power, it was also heard even weaker.

I set up a workstation overlooking the mast. See photo:

Nejdříve jsem s dolaďovacím pístem nastavil na maximální signal přechod WR42/SMA. Nastavení odpovídá popisu dle WA5VJB.

It was quite wide at the top piston. When the piston was fully extended, the signal was – 10 dB weaker. The setting value is optimal as indicated in the AIY drawing. See photo:


Signal with double window closed / 50 years old/ 599 + 20 dB

Signal with open window 599 + 35 dB.

The SLOT antenna was set to about 45 degrees due to the elevation difference between the transverter and the beacon.

I also tried some kind of SLOT cover not only for attenuation but also to be able to withstand altitudes above 700 m/m. I found a plastic wrapper from some soda, some pipe from a dismantled printer, and a Pe tube for water. All these materials did not visibly reduce the performance of the beacon. So I decided to put the Pe tube in. So all that’s left is to put the beacon in the box.

Translated with www.DeepL.com/Translator (free version)

Picture: from original article OK1EM

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