The next QRP project?

Having finished the 500kHz transverter to my satisfaction I'm mulling over the next project "big idea" to keep me amused on a winter afternoon. I do want to build some homebrew gear for 28MHz as this remains one of my favourite bands: antennas are small and unobtrusive, DX is not hard to work with QRP when the band is in good shape, and the frequency is low enough to be able to make gear, and get it working, with my limited test equipment. Maybe I should do it in stages:

1. A direct conversion mixer and back end with CW/SSB filter bandwidths.
2. A direct-conversion 28MHz front end mixer and RF filter based on an SBL1 or NE612/602.
   
3. A stable mixer-VFO covering the CW and SSB part of the band.
4. A driver and PA for up to 5W.
5. A DSB mixer module to use with the above to use in a simple DSB transceiver.

Scottish DX on 500kHz

After no luck on CW I returned to 500kHz WSPR and was immediately rewarded with 3 spots including one from GM4PMK in the west of Scotland in IO66 square some 615kms to the north west of me. He's spotted me before but this is my first report from him in several weeks. He is reporting Andy G4JNT some 20dB stronger than me, which is consistent with the difference in ERP (Andy is running 200mW ERP and I am running around 1mW ERP).

500kHz CW activity tonight

Several DX stations on tonight on 500kHz CW. OR7T was calling LA3EQ (recently allocated the band in LA) and OZ8NJ was a good signal working G3DXZ. So far tonight, with all this excitment, no-one has heard my 1mW ERP signal on the key! WSPR is much easier!

500kHz full transceive transverter with 5 extra parts only ..and no relays!

I've now modified my WSPR tx up-converter to a full TX/RX tranverter suitable for WSPR, QRSS and CW  in a very simple way, making use of the FT817 split facility which allows you to RX on 500kHz and TX on 28MHz. By adding a series LC between the TX PA and the FT817 input/output RF connection (with back-to-back diodes at the L and C junction, this allows "pass through" from the 500kHz ATU to the FT817 on RX (tuned to 500kHz). On TX, the diodes conduct and the C part is in parallel with the first cap in the TX low pass filter. This scheme is now working really well with good RX sensitivity and no change in TX power out.

500kHz WSPR summary (1-2mW ERP or less)

After about 3 months on 500kHz WSPR, I've now been decoded by 44 different stations in 19 grid squares in 7 countries with best DX still SM6BHZ at 951kms.

Today I got some reports from Sam G4DDK, better known for his RadCom microwaves column - nice to see him listening on 500kHz.

10m/40m WSPR

This afternoon, for a change, I've been putting out a signal on 10m WSPR as my vertical on 500kHz can be resonated on 28MHz using the Elecraft auto-ATU. So far nothing heard here and no reports.

All was quiet so I moved to 40m where instant reports at 5W, then 500mW, from all over Europe. Now testing at 50mW output.

New grid square and station report on 500kHz

Just got my first WSPR report from Brittany, France from F5JNV in IN98 square at 427kms. This is now my 41st report so far on 500kHz. A 42nd report was received from a G SWL a few minutes later.

SAQ (17.2kHz): extra transmission Dec 10th 2009

There will be a CW transmission with the Alexanderson alternator at SAQ on 17.2 kHz on Dec 10th 2009 at 08:00 UTC and again at 16:00 UTC the same day.

The reason for the extra transmission is a centenary commemoration of the Nobel Prize given to Guglielmo Marconi and Karl Ferdinand Brown. SAQ does not want QSL-reports this time and will not verify. They still intend to continue with their annual transmissions on Christmas Eve (morning), Dec 24, at 08:00 UTC with tuning up from 07:30 UTC.

This is always a great opportunity to try your hand at VLF CW reception either with a simple up-converter, direct conversion RX or even a software receiver totally implemented on a PC.

Back on 500kHz WSPR (TX)

Having just got some more IRF510 FETs from the GQRP club I've rebuilt my 500kHz PA and got it working properly towards class E. As long as the antenna is close to 50 ohms the PA hardly gets warm (on a WSPR TX cycle at 5W RF from the PA) as the efficiency is now so good.

Will run the 500kHz WSPR beacon overnight tonight then plan to modify the PA and ATU to 136kHz for a few days. 136kHz WSPR tests will run over the weekend if things go to plan. ERP will be even lower than on 500kHz, but I'm hopeful of some reports. If you get a chance to listen and report (via the WSPR database) I'd be most grateful.

The new TX PA is working well: I've had a 0dB S/N WSPR report from F6CNI near Paris!

RXing on 500kHz this evening

Although I cannot TX on 500kHz at the moment (should be back on next week), I am listening again this evening and hoping to copy G3ZJO who is testing his station on WSPR. Not heard him yet but will keep listening.