Homebrew 30m DSB WSPR transceiver under test

Testing a homebrew direct conversion double sideband WSPR transceiver on 30 metres.

WSPR is a slow-speed narrow bandwidth digital mode that can be decoded even if signals are below the noise level.

WSPR takes 2 minutes to send two words. This is too slow for conversational purposes so it finds most use as a beaconing system for propagation testing and research.

Milliwatts of WSPR can be decoded thousands of kilometres away and the transmitting gear needed is very simple as this video shows.

The transceiver, which plugs into a laptop computer, has just four transistors. One is in the crystal oscillator, another in the receiver audio amplifier and two in the transmitter driver and final. The balanced modulator is used as the receiver product detector and uses two IN4148 diodes.

This is a very bare-bones rig. The concept is similar to the W3PM rig (see website below) but it's only double sideband (not SSB) and uses manual transmit / receive switching.




The receiver is prone to false spots and requires further work (possibly due to interference from the computer). However the transmitter is working very well, as the long-distance reports indicate.




Anyone wishing to build something like this is should start with W3PM's transceiver for a well-designed but simple design with good performance (link below).

This project was inspired by an item on the Soldersmoke podcast/blog about DSB WSPR. Even better was that 30 metre activity was around a frequency whose crystal I had in the junk box (although popular WSPR frequency crystals are cheaply available from oveseas). Following links led me to W3PM's site which describes a simple WSPR transceiver for 30m.

More info on WSPR below

* See whose hearing whom at http://wsprnet.org/drupal/

* Download K1JT's free software: http://www.physics.princeton.edu/puls...

* Soldersmoke http://www.soldersmoke.com

* W3PM's homebrew SSB WSPR rig: http://www.knology.net/~gmarcus/

* M0XPD's homebrew WSPR: http://m0xpd.blogspot.com/2010/05/homebrewed-whispers.html

* G3XBM's QRP and homebrewing: http://sites.google.com/site/g3xbmqrp/

Category:

Science & Technology

Tags:

• WSPR
• amateur
• ham
• radio
• QRP
• digital
• modes
• homebrew
• direct
• conversion
• DSB

[Lingubot]

Good job Peter!

Qoud you provide the schematic of this setup on your page please?

[CX2ABP]

Awesome, Peter! 73 de CX2ABP.

[GeoN0JRJ]

Very cool. I am going to build the Genesis G59 QRP transceiver and want to run WSPR on it once completed.