85 unique reports now on 500kHz with 1mW ERP

With a report yesterday from PA3EGO, the number of stations who've reported my signal on 500kHz WSPR and CW has now risen to 85 so far since last September. It's pleasing to see new DX reports coming in despite the less effective antenna now in place i.e. the 10m halo and its 5m of feeder coax. I'm actually finding the reports are not that much down, if anything, on the top spiral loaded vertical.

iPOD - 1940s style

This was posted on the QRP newsgroup today. Wonderful idea.
http://www.retrothing.com/2010/03/vacuum-tube-radio-hat.html

VKs coming through on 10m CW

VK6DXI was a good signal (579 at times) in the BERU contest this morning on 28.006MHz CW. I called several times with my 5W QRP but did not get through. Conditions on 10m are on the up!

8.97kHz VLF grabber on-line in Germany

DF6NM in Nuernberg, who has been successfully experimenting with sub-9kHz communications now has a temporary grabber on-air to capture any amateur signals on 8.97kHz.  See http://www.mydarc.de/df6nm/vlf/vlfgrabber.htm

500kHz CW QSO this evening

For a change I went on 500kHz CW and managed to get a 579 report from Chris G3XIZ. Chris then went on to work PA0WMR although the Dutch station was only about 559 with me. I called him but he did not hear me.

Useful American sub-9kHz experimental VLF site

VLFradio.com is a most interesting site. Among the stuff there are the results of some induction communications tests with a 90m circumference TX loop out in the desert away from man-made interference. Using just 0.5W a range of 1 mile (1.6kms) was achieved at 1.8kHz and with higher power up to 2 miles (3.2kms). These signals were copyable by ear, so further still would be possible with weak signal techniques. Also on the site lots of recordings of these tests as well as other VLF noises and man-made transmissions

Another country using the "degraded" (?) 500kHz antenna set-up

As I mentioned a few days ago, I took down the main 500kHz vertical so I could re-erect the 28MHz wire halo with coax feeder. I'm using this, with feeder inner/outer strapped, as the antenna on 500kHz now. Actually the reports aren't much worse! This evening I got +1dB S/N from F6CNI which is a typical report from him at 418kms on WSPR.

Sub-9kHz induction comms resource

John F5VLF/G3PAI has brought a very useful website about induction mode communications below 9kHz to my attention. This site is mainly about cave location and beaconing systems, but there are some neat schematics for local coverage (thousands of feet range) TX and RX circuits that would be suitable for QRSS and similar experiments in the "Dreamers Band" as some have called it. See http://radiolocation.tripod.com/

Sub-9kHz Induction Field DX?

With all the discussion recently on the LF Reflector about how to radiate a signal on sub-9kHz I'm left wondrering how far, practically, one could expect to get simply with sub-9kHz electromagnetic induction using multi-turn loops at each end.

It's quite easy for anyone to generate 50-100W or so and feed this into a largish diameter multi-turn loop. Correctly aligned and with a similar loop at the far end and using decent weak signal processing just what range might be possible using modes like QRSS or WSPR? Has anyone tried this to see just what is practical, simply using induction fields?

The Cave Radio Group (CREG) may have some answers but I'm not a subscriber so can't read any of their documents.

LATER: Jim Moritz M0BMU did some sums (see my webpage on sub-9kHz radio) and reckons that about 4.4kms is the best one could do with 100W and a 10m diameter loop and purely inductive communications. More power and bigger (low loss) loops could get a bit further still.

9kHz band receiver front-end (M0BMU)

Jim M0BMU has produced a neat loop/preamp design suitable for listening on the 9kHz band for which we hope NoVs will be available shortly in the UK. His design has sufficiently low noise to provide a state-of-the-art receiver for this band when used with the many excellent software based VLF receivers such as Winrad and Spectrum Lab. This circuit was posted on the LF Reflector this evening.