Shall We Upgrade From Short Wave Listening to ‘Microwave Listening’?

Most of us radio amateurs have nostalgic memories of short wave listening and we were called SWLs by radio amateurs. I still remember my SWL days in 1970s, listening to powerful ham radio stations in this region on amplitude modulation like VU2TG and VU2JN using my home broadcast receiver Philips Prestige, a four band vacuum tube radio.

In those days only microwave activity in this region were the microwave towers which we used to see here and there, relaying long distance telephone calls. I used to visit as many towers as possible and once I got the chance to have a telephone call from one of those tower locations. Microwaves are radio waves in the range of 300 MHz to 300 GHz in broad sense. But there is variation in definition in that some consider it between 1 to 100 GHz or even between 1 to 3000 GHz. Anyway, the term microwave does not imply waves in the region of micrometer length, rather they are smaller than conventional radio waves. So microwaves may mean anything from Ultra High Frequency to Extremely High Frequency, depending on the definition which you follow.

Coming back to ‘Microwave Listening’, when I was an SWL, I was not even aware of the possibility of amateur ‘Microwave Listening’. When I became an amateur radio operator, some of the richer hams had VHF radios, which do not come under microwave category by any definition. Some time later, I noticed UHF hand held radios being mentioned in the catalogues of amateur radio dealers in this region. Those radios intrigued me as they were smaller and had smaller whip antennas, compared to VHF hand held radios. But I never had an opportunity to use one. When I returned to amateur radio after a long hiatus in 2023, things had changed a lot.

Many in this region had started operating on the QO-100 Geostationary Amateur Radio Satellite, located at about 36,000 km altitude, which was rather mind boggling for me! I was wondering how to listen to them, obviously in the microwave band with downlink on 10 GHz band. It was VU2NSL, who told me about the Qatar-OSCAR 100 Narrowband WebSDR by British Amateur Television Club (BATC) hosted at Goonhilly Earth Station. WebSDR is a relatively recent invention which allows us to listen to radio transmissions using a web interface in your smart phone or computer. It can be tuned to different frequencies simultaneously by multliple users located in any place with access to the internet. I started off by listening to the QO-100 India Morning Net on 10489.690 MHz between 7.15 am to 7.30 am IST (UTC+5.30) and I could hear VU2NSL controlling the net on most days. As it was from a geostationary satellite received with a 1.3m dish antenna at Goonhilly Earth Station, the audio was quite clear and I used to enjoy listening to the net daily till I got a new VHF/UHF dual bander radio a few months later. So that was my introduction to ‘Microwave Listening’!

If you go by the wider definition of microwaves, even my VHF/UHF dual bander radio is useful for listening to the so called ‘microwaves’ in the wider sense, the UHF radio waves, though I do not consider them as really ‘microwaves’. In that way you may consider that listening to the downlink frequency of Amateur Radio on International Space Station on 437.800 MHz as a lower level of microwave listening.

Recently I have started using VU3ZNG Open WebRX for listening to amateur radio satellites. V/U satellites with uplink on VHF and downlink on UHF like the Space Station can be listened to in this widened definition microwave region. You can also listen to U/V satellites with uplink on UHF and downlink on VHF like AO-91 using this Open WebRX. There are bookmarks for several satellites availble there for locating the frequency easily.

Unlike the QO-100 which is geostationary and can be accessed at any time, Low Earth Orbit satellites are available for only about 10 minutes during a pass in the region of the Open WebRX. You have to find the timing from sites like N2YO.COM by entering the Maidenhead grid location of the WebSDR. In case of VU3ZNG Open WebRX, the grid location is MK82tw.

On a side note, a very popular WebSDR for shortwave listening is the University of Twente Wide-band WebSDR. When I checked just now, there were 514 simultaneous users.