19 March 2012

Extremely High Frequencies

Some hams are breaking new frontiers by going up to extremely high frequency bands. In Sweden, Per, SM0DFP is one of the few. Last autumn Per set a new Swedish distance record on 47 GHz. The distance was 55 km over the Baltic Sea with 599/599 reports taking advantage of sea level ducting. The wave length is only 6 mm. The day before the first QSO between SM (Sweden) and OH0 (Åland Islands) took place on 47 GHz. The distance was then 44 km. On the other side on Åland Islands was Pertti, OH2AXH located with his 60 mW QRO (!) portable station. Per is a very skilled technician and also a contester on 1296 MHz and up. On this occasion also the first SM-OH0 QSO on 24 GHz took place. I do not have any info about Pertti´s background, but I suppose he can be ranked in the same division as Per. What took place at Per´s locations can be seen in the video below.



SM0DFP fixed station (JP90jc)
24 GHz: 0.5 W, 40 cm dish, 40 m a.s.l.
47 GHz: 0.2 mW, 25 cm dish, 8 dB NF, 40 m a.s.l.

SM0DFP portable station (JP90jc)
47 GHz: 20 mW, 20 cm offset dish (TX), 25 cm dish (RX), 5 m a.s.l.

OH0/OH2AXH portable station (JP90sf and JP90vc)
24 GHz: 1 W, 40 cm dish, 2 m a.s.l.
47 GHz: 60 mW, 25 cm dish, 8 dB NF, 2 m a.s.l.

Per is a member of SK0CT, an Ericsson Amateur Radio Club, located in Kista 10 km NW of Stockholm. Please visit Per´s interesting pages on the SK0CT web site, the section SM0DFP/Propagation for further reading.


I never reached higher frequencies than in the 1.3 GHz band. This was my setup in the living room (!) in beginning of 1978. I managed to have one QSO with the 1.2 m dish. The transmitter end stage was a homebuilt diode tripler. The diode consisted of at least 20 together soldered 1N4148s. The output power must have been in the range of only 1 mW. I think the QSO distance was ca. 40 km. Please note the 1 5/8" coaxial cables running over the sofa. Of course my wife did not like this setup, but my kids seemed to do that.


This is a terrible dish construction from the same year! It never worked. Now looking in my old logbooks I found that I had a QSO on 1.3 GHz on 15 June in 1978 with Per. I was on a hilltop and the antenna was of a helix type. My distance record on 1.3 GHz is 600,000 km set on 12 October, 2008, but this was via the Moon! The antenna then was a 1.8 m mesh dish and with 70 W at the antenna input.
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