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Monday, March 2, 2009

Homebrew WSPR from W3PM

Recently I've been reading with envy the WSPR reports from K6HX. Mark tells how he walks into his shack each morning and is greeted with signal reports from around the world. Beautiful maps are presented, with lines arcing from Southern California to distant islands in the South Pacific. I burn with envy. I want to WSPR too! But I have no SSB gear for 30 meters, and unlike our beloved visual MEPT QRSS, WSPR requires SSB gear.

I had mentioned all this on SolderSmoke, and this morning Gene, W3PM, came to the rescue. He sent info on a really interesting and very simple SSB transceiver. Take a look at the block diagram. On transmit it is essentially a DSB rig with a filter at the operating frequency to knock down the unwanted sideband. On receive it is a Direct Conversion receiver preceded by a narrow filter that allows the WSPR frequencies through. It uses the familiar SBL-1 mixer. The filter has only one crystal. And --icing on the cake -- Gene built his version in modular form, with each module in an Altoids tin. Clearly, this is the WSPR rig for us!

Gene provides a very nice write up on his project here:
http://www.knology.net/~gmarcus/WSPR/wspr2.pdf

1 comment:

  1. I am a long time WSPR fan, esp interested in VLF WSPR...and 10m. Been hoping to find 10m open more than "advertised", but still no decodes or reports of Beacons this Feb 2011.

    ...so moving down to 24.9261 MHz, I am often suprised to hear more activity and my first decode (below speaker copy!) was from
    W3PM. I soon located your info and am now going to build a similar xmiter...puting my 137 KHz project on hold. Antennea will much easier to deal with at this HF frequency !

    W3PM's 1 watt beacon travelled 1213KM to reach my QTH at a -15dB SNR...not bad for 1 watt, eh?

    WSPR sure has made radio fun again!

    73
    Greg
    VE3FAX
    FN04fc

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