500kHz transverter (breadboard) photo

This is a photo of the 5W 500kHz transverter breadboard in its "raw" state. In the next couple of days it will be rebuilt tidily into a small aluminium project box and should look a lot neater. Still, isn't it amazing that something this rough on the bench top can work so well and be heard 951kms away!

Power harvesting IC - runs off 20mV produces 5V

This week's Electronics Weekly has a link to Linear Technologies new power converter IC (LTC3108) that can run from 20mV and deliver 5V. It is designed to be used with Peltier effect devices and similar sources of low voltages, but it could be used with the DC power derived from a crystal set.

Weather and 500kHz antenna matching

It surprises me how much my antenna matching changes depending on weather, temperature etc. I use my simple ferrite rod ATU for the main antenna tuning (tapping down the coil for best antenna and TX connection but I make final adjustments using my little Elecraft auto-ATU at the shack end of the feed coax to the remote ATU in the back bedroom near the antenna. If it rains or the weather is cold, I need to rematch the T1 ATU to get best SWR.  I guess this is all due to the ground losses changing in wet weather as a result of changes in soil conductivity.

A new report from Germany on 500kHz

Last night I was copied, just, at -30dB S/N, by Veit DL7ET in JO31 square at 468kms. This is now my 47th unique station report on the band (well 49 if you include 2 CW contacts). At some point soon the antenna for 500kHz will have to come down so I can re-erect my 28MHz antenna, but maybe not for a couple more weeks.

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.