31 Dec 2010

VLF success at last for G3XIZ (37km on 8.97kHz)

Chris G3XIZ achieved some VLF success today when his 50m high balloon supported vertical driven with around 50W was copied at up to 15dB S/N by M0BMU at a distance of 37km. Mode used was QRSS600. This is a new UK record for an amateur VLF transmission and is the first confirmed "far field" radiated signal. Well done Chris.

M0BMU estimated the ERP as follows (from a posting to the LF-reflector by Jim):
"I made an estimate of the field strength of your signal by injecting a test signal at a known EMF into the loop antenna, and comparing with the level of your signal. The received FS at the strongest point (around 1330utc) worked out to be 1.8uV/m. Taking the distance between our locations as 37km, your ERP would have been 87uW. The SNR at best was around 15dB, making the noise level 0.32uV/m in the FFT noise bandwidth of 2.1mHz, or a noise density of 7uV/m per sqrt(Hz)

Assuming a 50m vertical wire (heff ~ 25m),  Rrad of your antenna at 8.97kHz would be 880micro-ohms. Assuming 2.62dB directivity for an electrically short monopole compared to a dipole, and Iant of 200mA, the calculated value of ERP would then be 64uW. So there is reasonable agreement between these two calculations, the difference only being 1.3dB."

29 Dec 2010

Night time SAQ VLF transmission - Jan 4th 2011

There will be an extra transmission with the Alexanderson alternator on 17.2 kHz primarily for listeners in North America, the times shown below. QSL cards will be issued for correct reports. These can be sent via post, email or via the SM QSL bureau.

16:00 PST (Pacific Standard Time) in USA. Monday, Jan 3rd, 2011 
19:00 EST (Eastern Standard Time) in USA. Monday, Jan 3rd, 2011
00:00 UTC (Coordinated Universal Time) Western Europe. Tuesday, Jan 4th, 2011
01:00 CET (Central European Time) and local time in Sweden. Tuesday, Jan 4th, 2011

28 Dec 2010

Diurnal Variation in Dreamer's Band Noise

Over the next 24 hours I am doing a test to measure the change in VLF noise floor between 0-24kHz. DK7FC has let me have a suitable .usr file for Spectrum Lab to allow this to be recorded. You can see the results on the G3XBM VLF grabber which is updating the plot every 15 minutes.

Surprise late afternoon 10m opening to the USA

WSPR reports 10m on 28.12.10
Late this afternoon I was surprised to see that 10m opened up to the USA and that my QRP WSPR beacon was being received well at up to 6991km with reports at 5692km from K3ZV as late as 1800z with my reports of USA stations being the last ones to appear, meaning I was receiving stations when others were no longer doing so. Power was 5W and the antenna the Homebase-10 wire halo.

27 Dec 2010

G3XIZ on 8.97kHz today

Chris, G3XIZ was testing on the Dreamer's Band again today and I was monitoring some 34km to the east. Unfortunately, this attempt was also unsuccessful with no copy here in East Cambridgeshire.

Iceland get big 500kHz allocation

493-510 kHz has been granted on a secondary basis to amateurs in Iceland with a power limit of 100W. In addition, 60m and 4m allocations have also been confirmed.

26 Dec 2010

Dutch hams lose 500kHz (for now)

Stations in The Netherlands who were active on 500kHz will have to stop transmitting at the end of 2010 as their permits have yet to be renewed. It is expected that this will happen within 4-6 weeks.

25 Dec 2010

Christmas WSPRs

Very quiet on 10m WSPR today, Christmas Day. Just G3JKV coming through from 123km to the south of me on tropo. WSPR is an ideal mode for Christmas day as one can set it running, go eat the turkey and trimmings and periodically check results.

24 Dec 2010

Merry Christmas everyone

Whatever your circumstances I hope you have a peaceful and happy time this Christmas shared with the people you love.

22 Dec 2010

G3XDV on 136kHz QRSS

Getting a very strong signal this evening from G3XDV on 136.177kHz QRSS60 receiving Mike on the earth electrodes fed straight into the deaf (at 136kHz) FT817. He is sending "XDV" preceded by G3XDV in normal speed CW.

19 Dec 2010

160m QRP DX on WSPR

WSPR reports - 160m 5W QRP
Last night I used my 5m long vertical feeder to the 10m halo as a TX antenna on 160m WSPR, matching it with a few turns on a ferrite rod on the bedroom table and the Elecraft T1 auto-ATU. Results were very encouraging for 5W and an indifferent antenna with best DX reports from Norway and Spain. On RX the best DX was RA3LW at 2036km.

18 Dec 2010

160m DX on WSPR

Last night I decided to take a look on 160m WSPR to see what could be heard/seen with my strapped feeder up to the 10m halo as an (untuned) vertical. 21 unique stations copied and best DX was K9PAW (running 2W) at 0222z who is 6370km away. I may now try some overnight TXing with this antenna properly tuned and matched to see how far away my own QRP WSPR signals can be heard.

17 Dec 2010

13cm handheld "DX" QSO

My iPod Touch 4g has the free Echolink app installed and last night, when I went to bed, I decided to give it a try. I managed to work a mobile station in Brisbane, Australia using the Brisbane repeater. In effect, the iPod Touch is used as a 13cm QRP handheld transceiver (using the 802.11 wi-fi functionality). Fun, with simple operation and good audio reports. I continue to be amazed by the iPod Touch 4g which is a truly amazing piece of kit for around £160. There are very many useful amateur radio applications including a free oscilloscope and audio spectrum analysers and spectrograms for a few pounds only.

16 Dec 2010

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.

14 Dec 2010

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.

12 Dec 2010

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.

Carrier "on" periods of 30mins or more

Good luck to anyone having a go.

Roger G3XBM


10 Dec 2010

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.

9 Dec 2010

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.

8 Dec 2010

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.

7 Dec 2010

DK7FC's report on his 9th VLF experiment

DK7FC with his VLF loading coil
Stefan has summarised the results of his latest tests on VLF. This is well worth reading with best DX 2873km and lots of new stations receiving his transmissions for the first time.

This picture was taken by a friendly visitor and there are more pictures at http://mkorbit.de/2010/12/05/weltrekord-signalubertragung-auf-einer-langstwelle-vlf/

USA on 10m

At 3pm this afternoon KC2GMM was coming through on 10m WSPR at -25dB S/N when running 10W. Another example of the power of WSPR to spot the fleeting openings.

6 Dec 2010

Realtime Propagation Charts

G0KYA has a most useful page offering realtime propagation predictions in the form of maps showing exactly where signals should reach on a given band at a given time of day. It uses the latest available solar data so should be a very good guide. The maps assume 100W and a dipole at medium height, so for a QRP station the results to be expected will be less good.

5 Dec 2010

VLF real DX: 2873km on 8.97kHz

Yesterday, Sat Dec 4th, DK7FC's VLF signal was copied by 4X1RF at an astounding distance of 2873km. Signal levels suggest that transatlantic reception may indeed be possible in the near future. Many other stations also copied Stefan's signals on various VLF frequencies yesterday. Congratulations to Stefan and everyone else who managed to copy his signal.

4 Dec 2010

Full QTH locator square? Find it here

Just discovered that my full QTH locator is JO02DG85VD . This was found using a website I'd not come across before http://no.nonsense.ee/qthmap/ .


For the first time I tried WSPR on 2m this evening. G4IKZ at 18km was a VERY strong signal but with a huge amount of Doppler shift which meant he did not decode. I've just seen G4IKZ has spotted me at +3dB S/N though, so perhaps it was just a passing plane.

DK7FC's 8.97kHz signal copied today (and in Israel!)

Weak signal around 8970.0Hz
Today I managed to weakly copy DK7FC's latest test transmission on 8.97kHz using my 20m spaced earth electrode and small FET preamp. Spectrum Lab, locked to a VLF MSK transmission helped by allowing me to look at precisely the right frequency. Distance is 648km. Stefan's signal was also copied in Israel, quite remarkable DX.

3 Dec 2010

My VLF grabber on for DK7FC's tests on 8.97kHz

My frequency locked VLF grabber using Spectrum Lab software, running at QRSS600 speed (i.e. slow and narrowband),  is now active until Saturday evening in the hope I may see a trace of DK7FC's 9th VLF "kite antenna" transmission on 8.970kHz on Saturday. He will be using both QRSS and DFCW. He hopes to run up to 100mW ERP this time.

2 Dec 2010

DK7FC on 8.97kHz this weekend

Stefan DK7FC is making preparations for a further test transmission on 8.97kHz this weekend. Saturday is his preferred day but if winds to support his kite antenna are too low, it may be Sunday. As usual, he will use very slow QRSS and DFCW.  During his last transmission he was received at 1310km and in a number of European countries.

1 Dec 2010

8.76kHz field testing in the snow at 1.5km

With a temperature around 0 deg C I did a field trip today TXing on 8.76kHz VLF to test two things: (1) to check the rebuilt 4-5W TX based on the TDA2003 could be copied at moderate range and (b) to try out the new tuned preamp with earth electrode receive antennas and see how these compared with a loop. The usual first test site, a National Trust car park about 1.5km from home was chosen. Today it was totally deserted with more sensible people curled up in front of warm fires. Using the 80cm receiving loop or with the earth electrode antenna (electrodes placed about 13m apart) decent
copy was achieved in QRSS3, using Spectrum Lab this time rather than Spectran on the PC.  For the earth electrodes I just used barbecue skewers pushed in about 10cm into the very cold ground. Reception was also possible with the two earth electrodes just 2m apart. The first picture shows the signal received with a loop. The second is with the earth electrode antenna on receive. The ground was covered in a thin layer of wet snow and results when the soil, and soil surface, are dry should be better on earth mode conduction using earth electrodes at each end. The roads in the Fens were too icy to try reception at a more distant point 5-6km away. Also, I need a much longer baseline earth electrode pair in the car in case this is needed at greater range.