Icom R20 as SDR?

[Gasmansteve]

HI folks
I`m wondering how/if the R20 can be used as an SDR receiver at all?. Software seems to be a bit sparse for controlling this receiver which to be fair to the R20 it seems quite an old model now and maybe not really designed for pc control although I have been reading good things about its use with Ham Radio Deluxe and also KE7ATE. The specs for the R20 seem to be top knotch for a HH type and I`m hovering over the `Buy` button to get one even though they are still quite pricey over here in the UK and there doesn`t seem to be an R30 in production as yet. I understand HF reception is fair to ok with the right antenna and some guys on youtube have decoded satellite images with it so all in all it seems an exceptional piece of kit!
regards
Steve

 

[LesWurk]

I'm sure you would have to get the soldering iron out. On a new under warranty receiver that might not be the best idea. The Alinco Djx-11 can do SDR with limited bandwidth. Third party software needed of course.

 

[Gasmansteve]

Hi LW
I did wonder about that at first but have been in contact with the author of KE7ATE and he assures me just a lead like this Cat programming Cable for Icom radio IC-R20 scanner CI-V CT-17 with audio output | eBay is all thats needed (with a usb to serial lead if no serial socket on pc!) .
best
Steve

 

[Token]

Are you confusing the terms SDR (Software Defined Receiver) and SCR (Software Controlled Radio)?

The R20 is a traditional superhetrodyne receiver, by definition not an SDR. Just like any superhet radio made you can, of course, tap the IF and put the signal into a digitizer (SDR), resulting in a hybrid system, with the traditional radio as the front end and the digitizer performing the demodulation. That would NOT make the R20 an SDR, but rather a downconverter or upconverter for an SDR.

Some radios are delivered with the IF already buffered and brought out to a jack. This practice far predates SDR, but as long as the IF is before any filtering this is a great way to make a relatively low end SDR become very wide ranged in frequency.

Some radios, like the Alinco DJ-X11 and the DX-R8T, include an added feature of bringing the I/Q data out to a port, then you can put that data into a digitizer and have the affect of an SDR. That does not make either of these radios an SDR as such, but does blur the lines between a traditional radio and an SDR. When you combine these radios with a digitizer (your sound card in your computer is a dandy one) and appropriate software you have created an SDR.

T!

 

[Gasmansteve]

Ah! thanks for the explanation T. Forgive the newb logic but I thought what I was doing with the Funcubedongle was SDR and assumed that using/controlling an R20 with a pc was also SDR. I found it interesting using the Funcube dongle with software such as SDR# and Spectrum lab etc to observe meteor scatter with my Yagi pointing to the Graves beacon in Dijon France at 143048kHz. So using the R20 for stuff like decoding satellite data for instance would not be classed as SDR because its not IQ data just simply audio...right?
So looks like the R20 is not the ideal receiver to go down the SDR route, I`ll check out more of the others you suggest.
thanks again
Steve

 

[Token]

Ah! thanks for the explanation T. Forgive the newb logic but I thought what I was doing with the Funcubedongle was SDR and assumed that using/controlling an R20 with a pc was also SDR.

The Funcube is definitely an SDR. However many conventional radios can be controlled by computer, and just because the radio is controlled from the computer does not make it an SDR.

Exactly what an SDR is can mean different things to different people, however the basics are that certain stages done in hardware with a conventional receiver, things like mixers, filters, demodulators, and detectors, are done instead in software (or firmware) with the SDR.

Some SDRs are “true” SDRs, everything is done digitally, this is a relatively new realm. A high speed A/D is attached to an antenna and the output of the A/D is then handled in software. This is sometimes called Direct Digital Conversion.

More common (because of cost) is the use of a local oscillator and a mixer in front of the A/D to bring the desired tuning range down to something a lower speed A/D can deal with. The Funcube Dongle and the RTL SDRs fall in this class. An extension of this technique (and probably the oldest hobby SDR family) is the sound card family of SDRs, like the SoftRock series. They mix the signal down to baseband and process it to I/Q data, and then the users PC sound card takes that baseband I/Q into the right and left channels, with software doing the rest. This moves the A/D out of the receiver and into the PC, the soundcard is the A/D in this case.

The next logical extension of this (and the technique that has been in use the longest) would be to use a conventional superhetrodyne design and replace only the final IF or AF detector stage with a digitizer. This technique has been in use for many years and was generally called “DSP radio” before the term SDR really caught on. Radios like the Yaesue FTdx-5000 (IF) and Kenwood TS-2000 (AF) use this technique. If the signal is ever digitized before it is detected it is probably valid to call it SDR, although at a personal level I don’t think DSP radios should be called “SDR”.

I found it interesting using the Funcube dongle with software such as SDR# and Spectrum lab etc to observe meteor scatter with my Yagi pointing to the Graves beacon in Dijon France at 143048kHz. So using the R20 for stuff like decoding satellite data for instance would not be classed as SDR because its not IQ data just simply audio...right?

Using the R20 is not SDR, regardless of how the data comes out, because the R20 does everything in hardware before putting out the detected signal. And then, yes, the detected signal is put out as audio.

Simply taking that detected audio and running it into spectrogram software does not turn the whole thing into SDR. However it is still a valid way to detect such things as meteor scatter and Doppler shift caused by motion.

For example, if I take an Icom R8500 (or any other RX with appropriate tuning range and modes) and monitor the pilot tones of LA TV stations (LA is a good ways away, but still works for me) I can detect aircraft in flight by their Doppler shift of the pilot tone. But that does not mean I am using an SDR or SDR techniques. Picture below:

So looks like the R20 is not the ideal receiver to go down the SDR route, I`ll check out more of the others you suggest.

Since the R20 is not an SDR I would have to say it is not a good radio to go down the SDR route What are your goals? What is your target set?

T!