Sunday, 7 March 2010

Whispering on 40m




I've been interested in K1JT's "WSPR" mode since hearing about it on (I guess) Soldersmoke - but it wasn't until Mike, G4VSS, spoke about it at the club recently that I was moved to action.

I download the software a few weeks back and I tried listening on my pre-historic FT101ZD.

Unfortunately, that rig doesn't have the sort of accuracy (nor stability) in setting frequency required for WSPR operation (the band is only 200 Hz wide), so I decided I needed something better and put the idea on hold.

Well, whilst in HB-land last week I was planning "something for the weekend" - I decided to revisit WSPR - this time using my SoftRock RxTx v6.2 Software Defined Radio.

It has all the features required...
1) stable, controllable tuning (especially with the USB synthesizer from Jan, G0BBL)
2) flexible Rx filtering
3) Appropriately QRP output

The first thing to do was struggle back up the learning curve with my SoftRock - it is one of those things where there are so many details that I forget them if it hasn't been used for a while. Here's the hardware...



The SoftRock is to the left, with the case lid off as I still haven't got around to packaging up the USB-synth (right) yet.

Previously I hadn't got past using Rocky with the USB Synth - this time I wanted to use PowerSDR (as it has much more flexible Rx filtering. I first downloaded the latest version for use in Rx...



I've used Eugene Muzychenko's "Virtual Audio Cable" to connect WSPR and PowerSDR - works well.

Yesterday I started receiving on 40m and got the following spots...



Today, I loaded the special version of PowerSDR for SoftRocks - "PowerSDR-SR40". I tried transmitting and I could put out 500mW on my G5RV - but was getting nowhere fast, until I checked the frequency of the USB Synth. This was slightly out and - once adjusted - I quickly got spots over Europe...



This has been great fun - I'll be doing more whispering in the future!

...-.- de m0xpd

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