Discussion in 'Software Defined Radio (SDR)' started by N3AWS, Dec 22, 2018.
Great article in Jan 2019 QST by Ron W5RKN.
Must read for those who work the birds!
Since I don't get QST, I've not read the article. BUT, I do use an SDR to listen in on the various satellites. They work GREAT.
Yes, a good article. W5RKN wrote a similar article a few years ago for the AMSAT Journal on the same topic. It's nice to see an updated article with his current setup.
In 2015, I wrote articles that were published in the AMSAT Journal and AMSAT-UK's OSCAR NEWS about using an SDR receiver for the satellite downlinks. Unlike W5RKN, I don't have Flex radios - I use an FT-817 for my uplink radio, and the SDR receiver was working with a small Windows tablet for the downlink radio. When these articles were written, Windows 8.1 was the operating system on the tablets. The articles still apply with the current crop of tablets with Windows 10.
I went with Windows tablets for SDR in the field, as I didn't want to carry a larger laptop with me, and the other tablets with iOS or Android didn't have the options for software as Windows. Unfortunately for the tablets, the touch screens really don't help with using some of the functions in the software, but a Bluetooth mouse helps with that (and doesn't take up a scarce USB socket, like other wireless mice). Maybe future software/apps will take advantage of touch screens, but the mouse has one thing that helps with SDR software - the mouse wheel can be configured to act like a VFO knob.
It's great to be able to see the entire transponder from a satellite. You see all signals that are coming through, and simply clicking on the trace in the waterfall takes you to that frequency. SDR software like HDSDR can be controlled by other software like SatPC32 to do Doppler fine-tuning automatically, and - if the uplink radio, like my FT-817, is connected to the tablet - SatPC32 can also control that radio at the same time. Subject to available storage, the SDR software can record the entire transponder, and not just the frequency you are working. It is nice to be able to go back and see who else was on a pass, stations I might have missed.
Thank you for advancing the state of the art in our hobby. Merry Christmas to you and yours!
SDR receivers are an option for those trying to build a station capable of working satellites in SSB or CW. Many start with using a pair of FT-817s, or an FT-817 and something capable of receiving SSB/CW at 2m and 70cm. Two FT-817s (or, now, FT-818s) aren't a cheap proposition. Some radios like the Kenwood TH-D74 HT include an all-mode receiver that works well for satellites, but a TH-D74 isn't cheap either.
I first tried an inexpensive RTL-SDR dongle for receiving amateur satellites. There isn't any front-end filtering to speak of in these dongles. Moving up to something like the SDRplay receivers or the FUNcube Dongle Pro+... now those have front-end filtering that works. Not as cheap as an RTL-SDR dongle, but I don't want to use the inexpensive dongle and then have to use external filters that the other receivers include from the factory. Some have been successful with the RTL-SDR dongles, and have used them to receive telemetry from various satellites, but that's a different use case than receiving on one band with a nearby radio transmitting on another band.
Merry Christmas, and 73!
Very true. I haven't worked satellites for years, but my last station consisted of an FT-817 (not the D model) for the uplink and an Icom 706 MKIIG for the downlink. Made my share of contacts, I suppose. Maybe when I retire next September I'll get back into that aspect of the hobby.
You can listen or talk to anything or band with SDR. In commercial radio markets, Super-Het and analog is on life support and not expected to survive.
Better still is the fact you see the noise floor come up as the pass begins, and if you need to, use that time to be ready for when you can actually use the bird.