Classic 10m DSB TX

There was an article, in 73 Magazine back in the early 1970s, about a simple crystal controlled, 1W 10m DSB transmitter. This was reprinted in a Dutch magazine and in RadCom. The schematic had at least one error (one diode in the mixer wrong way around, that I have corrected here), but it is a useful "ideas" starting point for a DSB transceiver. This circuit used PNP transistors. Today I'd use NPN 2N3904 devices and T37-6 toroids everywhere.

ON/F6CNI on 500kHz

This evening, conditions have been very good on 500kHz with almost continuous reports from GM4SLV up in the Shetland Is 896kms to the north. Also tonight, a new reporter ON/F6CNI in JO20 square at 424kms. His reports were very strong (-2dB S/N). This brings my total to 48 unique reports on 500kHz WSPR.  Tonight I've been using the new version of the transverter on the small, tidy, board (see picture on earlier blog entry today). This should be boxed tomorrow.

SAQ (17.2kHz VLF) reception

This link takes you to a recording of SAQ on 17.2kHz as heard by M0LMH in IO93 square.  It is quite strong when the signal starts. I listened on the Dutch online SDR and SAQ was not as strong there as I would have expected at 1600z. This is a recording of SAQ in Connecticut USA made by Jay W1VD earlier today.

Netherlands to get 500kHz

Full licence amateurs in The Netherlands can opt for an experimental permit to conduct experiments in the band 501-504 kHz with a maximum power of 5 W EIRP and a maximum bandwitdth of 100 Hz. The experiments will start on 1 January 2010 and will continue for one year maximum. News came via Rik OR7T and the RSGB LF reflector.

500kHz transverter rebuilt (and working)

This morning I rebuilt the 500kHz transverter in readiness for putting it in a small case. It fits comfortably on a 4 inch by 3 inch single sided piece of copper laminate built "ugly style". The unit worked first time and it has already received 4 WSPR spots from G3ZJO at lunchtime today.  The car keys give some idea of how small this unit is.

SAQ (17.2kHz) - on line receiver

Dec 10th the transmitter at SAQ (Sweden) on 17.2kHz is transmitting a special CW message. Also there is a transmission on Dec 24th. An on-line SDR in The Netherlands that can be used to listen to this. See  http://websdr.pa3weg.nl/ .  Alternatively, try listening with a simple up-converter or simple VLF receiver. 

Extra transmission on 10th December
In order to celebrate the 100th anniversary of the Nobel Prize to Guglielmo Marconi and Karl Ferdinand Braun, we plan to be on air on 10th December at 08.00 UTC and 16.00 UTC. No reports are required and no QSL-cards will be given.

Traditional transmission on Christmas Eve 24th December
SAQ will be on air on 24th December at 08.00 UTC. The frequency is as usual 17.2 kHz CW. Reports are welcome and will be confirmed by QSL-cards.

Latest sunspot predictions (from NOAA)

The very latest table of predicted sunspot numbers for cycle 24 have just been published on the NOAA website. They show a peak of 90 (+/-10) in May 2013. According to the table, the sunspot count will have risen to 45 by this time next year, so we should be assured of some regular USA contacts on 10m next autumn.

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.