Wednesday, 20 February 2013

My Fantasy VHF Band 2-FM SDR Receiver

After chatting to DX friends about the potential for a Super-DX Receiver for the VHF FM broadcast band (band 2) we accepted the fact that we're not quite close in getting that ideal DX machine. No, we're not quite there yet, but the technology is already here now. We just need the right software.

A good example of good hardware might be the Perseus FM+ add-on to the excellent Perseus SDR receiver. This piece of genius might have the necessary specification and performance a band 2 DXer needs, but the software, as good as it may be, doesn't quite meet our needs. So what do we need?

Speaking personally, I want a receiver which is able to scan up and down the band by itself, automatically storing instances of RDS PI and PS data. I need to be able to set various parameters such as: Continuous recording; Timer recording; Audio triggers for auto-recording; Date; Time; Frequency; Fully programmable scan/search and the ability to 'tick boxes' to select the specific data you wish to 'capture'. Above all, the RDS decoding MUST be highly sensitive and accurate at low signal levels.

Taking this a step further, there will be an internet connection to an online DX cluster such as FM List, where the captured data is automatically uploaded. This data will be cross-referenced to station lists and matched to automatically create loggings, thus producing an online logbook.

There's nothing like sitting in front of the receiver and tuning live, catching the DX as it happens, but during times when I might be away from the receiver or away from home, I would like to have the option to set the receiver recording the band and DXing for me. Before you say anything ... No, I really don't believe this is cheating!

I want to be able to play back the recording of the IF at my leisure so I can DX in real-time. Yes, I know, technically that's not "real-time", but you know what I mean. Such things are already happening in the world of amateur radio with many data modes. With current technology it is possible to record a maximum IF bandwidth of 4MHz of IF, but the VHF band 2 broadcast range is 20MHz wide. Two possible solutions would be: 1. To have the receiver scanning in blocks of of 4MHz, rapidly, like a kind of switched multiplex; 2. The software should be capable of running several instances of the software, simultaneously, without making my computer fall over. SDR# can already achieve the latter with the Climax DTV300 dongle!

Sadly, the DTV300 has fallen short on performance for some DXers, however. looking at the various SDR-control software packages currently available, one would assume the future looks quite rosy for us band 2 DXers. We still have to remind ourselves that this is a very niche little interest in what is already quite a niche hobby. There would be little financial incentive for a company to produce anything suitable on a small scale. In the meantime, we'll just have to rely on those clever programmers in our hobby who might be able to come up with something which exactly suits our needs! I hope we don't have to wait too long before such a fantasy DX machine will be readily available to us.

There might be a few bits and pieces I've forgotten and so I will add things along the way. For now, this is just a quick summary.

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