Homebrew USB port powered 30 metre WSPR transmitter

Testing a simple USB-powered WSPR beacon transmitter from a local beach.

As with my previous homebrew WSPR equipment, this one is double sideband. The transmitter (no receiver) has 3 transistors and puts out about 100 milliwatts. The USB power makes it much more compact as no external battery is required.

Stations hearing this so far have been VK4ZE and VK2DDI.

Check W3PM's website for the inspiration behind this and some circuits to start off with.

UPDATE 22/3/2011: Testing from home resulted in greater success - spots from ZL2FT, VK4ZBV and VK5ZAG.

Category:

Science & Technology

Tags:

• amateur
• ham
• radio
• digital
• WSPR
• portable
• QRP
• homebrew
• K1JT

[peterbmarks]

The WSPR2 documentation says "Be sure that your computer clock is correct to within about ±1 second". I guess if you sync before going out into the field you'd be ok for some hours but it probably wouldn't do for a camping trip with temperature fluctuations.

[vk3ye]

@peterbmarks Thanks Peter. One of the disadvantages of WSPR - but with such low power something's got to give.

[vk2tpm]

Great stuff Peter. Nice video production too! One reason for the lack of spots might have been clock drift - I wish there was a version of wspr that wasn't as critical of accurate time.

[vk3ye]

@vk2tpm Peter - I'd be curious how much clock drift affects things. I remember reading somewhere that 5 sec out was the limit, but surely drift can't be that much. Especially as I synchronise the computer's time before leaving home, so there's not too much time to drift.

[vk2ig]

Hi Peter, very impressive given your portable set-up and power from USB port of the laptop computer. My XYL and I liked your analogy of checking the WSPR spotting page with opening the chook shed door to see if there are any eggs - the latter is part of our daily routine here. :-) Cheers, Mike VK2IG/QRP