SAQ transmission on Dec 24th (17.2kHz)

The historic VLF alternator transmitter SAQ in Grimeton, Sweden will be transmitting next on Dec 24th at 0800z on 17.2kHz with tune-up some 30 minutes before. QSL cards will be issued for reports of successful reception if sent by email  to info@alexander.n.se or the SM QSL bureau (I think). This is a good chance to try out your VLF receivers. The antennas at Grimeton are a bit bigger than mine on VLF!

Long duration VLF test on 8.7608kHz yesterday

Yesterday I ran my 5W 8.7608kHz beacon into the earth electrode antenna on a quasi-continuous basis with transmissions of 30-60 minutes interspersed with 30-60 minute breaks. The tests lasted from 0900-2200z. Several stations between 25-70km were looking for my signals and Paul Nicholson up in Yorkshire has still to analyse his recorded files. So far, no station has detected any sign of the signal, which was not surprising considering the radiated ERP would have been in the pW level.  I was hoping that a few stations 10-20km  from JO02dg might have been looking as these would have had some chance of copying something. So, an unsuccessful test this time.

Paul Nicholson (Todmorden) advises me to use a GPS locked source so that the TX frequency is known with great precision. Then he, and others, can look for statistically significant weak signals at precisely the times and frequency of transmission. My HF crystal and divider source would not have been sufficiently stable to allow this sort of "digging in the noise" over any great time period.  For QRSS3, the current stability is fine. For the record, these were my transmission times: 0840-1000z, 1029-1229z, 1330-1500z,1531-1600z, 1630-1800z, 1830-1900z,1930-2207z on 15.12.10.

Yaesu FT450D (new version of the FT450)

Stateside magazines and websites are talking about a new version of the FT450 from Yaesu.  See the Universal Radio page about the FT450D. Apart from differently styled knobs and a couple of fold down feet - the original did not have a stand - I cannot really see what has changed. The FT450 has consistently got good reviews as a relatively inexpensive 160-6m 100W rig. As someone who has always been very pleased with Yaesu products right back to the FT7 days, I would consider this if buying a new HF radio for general use.

CamBeam Dec 2010

The latest edition of CamBeam the magazine of the Cambridge and District Amateur Radio Club (CDARC) is now available giving notice of future club activities and projects and of the upcoming AGM.  Currently I am a lapsed member of the club, although back in the early 1970s I was very actively involved when I first came up to Cambridge.

10m transatlantic F2 propagation today

Just got a -7dB S/n report from N4AU on 10m WSPR at a distance of 6976km. I believe this is my first 10m F2 report in many years. Not a bad report for 5W as it suggests the signal would have been copyable with about 25mW.

VLF very long carrier period tests Dec 15th

This Wednesday, Dec 15th, I will run tests on 8.7608kHz with very long continuous TX periods of several hours interspersed with gaps of 0.5 to 1 hour. Transmissions will start at 0900GMT and finish at 2300GMT. I will reveal the TX pattern after the test so the test is done "blind".

I'd be most grateful if suitably equipped stations could look for any possible signs of the signal, even though I shall only be using the 20m spaced earth electrodes and 5W as used for my local earthmode tests. Those able to screw the bandwidths right down may just be able to detect something, although I think it is unlikely at any great distance.

15.12.10    
0900-2300z 
8.7608kHz   
Carrier "on" periods of 30mins or more

Good luck to anyone having a go.

73s
Roger G3XBM

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How far is possible with earth mode on the Dreamer's Band?

A further observation from the test today: with 17dB above the noise signals at 5.1km using QRSS3 there is plenty of (theoretical) range still to be had with utilities assisted earth mode and just 5W.

Assuming 18dB loss every time distance is doubled (an inverse cubed attenuation rate for induction/conduction - is this right?) then almost 10km should be just possible, assuming the utilities that are aiding propagation are still there in the ground. Going from QRSS3 to QRSS30 should give another 8-10dB (see http://www.qsl.net/on7yd/136narro.htm#QRSS). Increase power from 5W to 100W gains another 13dB, so QRSS30 and 100W could give a range of some 20km by utilities assisted earth mode in favourable locations.

So, in some locations using the utilities buried in the ground all around us could offer some quite decent ranges with an earth electrode "antenna" at the TX end that requires minimal matching and no large loading coils, just a step-up transformer.

What is less clear to me is what exactly is the signal being carried along? Water pipes (often these are plastic now), overhead mains cables, gas pipes (usually non-metallic), phone lines, rivers even?

8.76kHz tests with loop + earth electrodes on RX

Today I did a test at 5.1km to compare reception of my 8.76kHz 5W transmission using (a) an 80cm loop antenna and (b) a small earth electrode antenna (14m spacing) using a variety of preamps.  Although quite solid reception (17dB S/N in 0.18Hz BW) was achieved using the loop laying flat on the ground, there was absolutely nothing detected using the earth electrodes, which was both surprising and disappointing. I used the very same preamp in both cases and also tried the lo-Z input tuned preamp with the earth electrodes that successfully copied DK7FC at 648km last weekend.

Several possibilities for the failure with the earth electrodes:

• The electrode spacing was far too small
• The barbecue skewers used as electrodes were too short and not making decent soil contact
• The soil was too wet, so the pick-up was lower than with dry, low conductivity soil. The test site is in the fens where the soil is a dark peat.

Next step is to repeat the test up on the chalk uplands to the south of the QTH where soil conductivity will be lower and to try a larger earth electrode spacing on receive.

A Homebrewer's Lab

VU2ESE's workbench - not unlike mine!

Ashhar Farhan VU2ESE has an interesting page setting out what basic equipment he considers a QRP homebrewer needs. See http://www.phonestack.com/farhan/lab.html. The only additional piece of equipment that I have found really useful is a small box to measure inductors and capacitors. The LC Meter kit produced by the Cambridge and District Radio Club has proved invaluable. A small spectrum analyser would also be useful, but these do not come cheap, although there are designs on the internet to make simple ones.

500kHz WSPR with earth electrodes

This evening I tried WSPR on 500kHz again using the earth electrode "antenna". 4 different stations reported hearing my sub 1mW ERP signal with best DX 417km to PA0A. Tomorrow I may try 500kHz with the vertical antenna to see how it compares, although I have to rebuild the ATU first.