30 May 2010


Just decided to do a little 6m WSPR beaconing this afternoon and evening. So far no reports of my signal, but I'm copying EA4BMG quite well. There are many more signals weakly visible on the WSPR screen but these have Doppler shift which must confuse the software decoder as only EA4BMG has been repeatedly decoded.

29 May 2010

Concorde to fly again?

There are moves afoot to get Concorde, the supersonic jet, flying again on memorial flights and it is possible it may yet fly over London at the 2012 Olympic Games opening. The only time I've been on Concorde was at Duxford Airport in Cambridgeshire in a static display. My wife's brother used to work for BT and fly to the USA and back in a day using Concorde so he could hold meetings in New York on a day trip - how times change!

See http://news.bbc.co.uk/1/hi/world/europe/8712806.stm

The latest VLF receiver

Here is a picture of the latest version of my VLF 1-2kHz receiver for use with my 80cm loop. The version before this (Wednesday) had one less Sallen-Key active high pass filter and was able to copy my 4W grounded electrode transmissions "by ear" at 0.5kms. This latest version now has 2 sections of 50Hz active high pass filtering so should offer better S/N at the limit of range. The audio above 2kHz is attenuated by the passive LPF.

28 May 2010

RockMite 20 QRP build video (N2JMB)

Just came across this video showing the build of a Small Wonder Labs Rock Mite 20 QRP transceiver.

27 May 2010

Portable crystal set DXing (in 1922)

Wonderful silent movie from 1922. See http://www.britishpathe.com/record.php?id=2616st5

Building a wax cylinder player

A band called The Men That Will Not Be Blamed For Nothing is putting one track of their next album on a wax cylinder available from 1 June. Don't ask me why! This is about an attempt to make a wax cylinder player to play the new record when it becomes available, the first commercially produced cylinder in 100 years.

See http://news.bbc.co.uk/1/hi/technology/10171206.stm

0.5km on earth-mode with 4W

This evening I achieved my best results so far with 1kHz earth mode TXing on a 20m base electrode pair and receiving on an 80cm loop and listening by ear. Even this range I think can be bettered with yet more 50Hz rejection. With a PC at the receiving end I think 1km is certainly possible now.

26 May 2010

Computer mouse problem

You must read this http://myweb.tiscali.co.uk/wgtaylor/FM.pdf . It is a true account of a PC problem that really did turn out to be a mouse problem ....a real mouse inside the PC that is.

25 May 2010

Resonating the VLF receiver loop

Today I've been resonating my receiving loop to see if this improved things. Well, I tried it - no better. Then I improved the active high pass (50Hz) filter which got the mains hum down some more, removed an audio gain stage in the RX just leaving 2 common emitter stages. With this, 4W TX, and the loop resonated around 2kHz I did a further walk-about test. 0.42kms was the limit of range. S/N better and 50Hz hum not a problem even close to cables. The RX needs some more gain and narrower selectivity.

24 May 2010

More earth mode experiments at 1kHz

This evening I extended my TX electrode spacings by connecting one end to the copper pipes in the house, almost doubling the effective TX baseline to about 20m. With this, my "earth mode" signals were much stronger and I was able to cover further than before in a "by ear" walk-about test around the fields locally.  Ultimate range tonight was 0.4kms using 4W (probably less as the TDA2003 was hot and probably turning down the power) and receiving on an 80cm 30t loop, active HPF, small AF amp and crystal earpiece.  Range was limited by 50Hz mains hum and background sferic noise. I must retry this set-up with my HF up-converter and FT817 this week, which has good rejection of 50Hz (and its harmonics) as well as a narrow CW filter.

San Marino on 6m QRP

Just worked T77C on 6m Es with QRP SSB. I think I've worked this station some years ago but it is one of the less common Europeans and a first for this season.

23 May 2010

6m Es

Only had a brief chance to operate today as I was busy in the garden then out at a BBQ in the hot sunshine, but managed to work some 6m QRP Es this afternoon. Although I worked some DX last week when out pedestrian portable, this was the first 6m Es QSO this season from home. In the coming weeks we can expect 6m to be open for DX most days.

22 May 2010

Tame Robin

Whilst out portable in Devon last week I was "visited" by this very tame robin who came so close he ate an ant from my hand. I was able to take a really close-up picture from about 20cms away. In the USA the American robin is a totally different, and larger, thrush sized bird. In the UK it is not uncommon for robins to be so tame they will come very close to you when gardening and they can be trained to eat from your hand. There was a good book called "The Life of the Robin" by David Lack published by Fontana in their New Naturalist series. This is no longer in print.

21 May 2010

Pedestrian Portable webpage added to site.

See http://sites.google.com/site/g3xbmqrp/Home/portable for my thoughts and tips on portable HF SSB DXing. If you have further thoughts or tips please let me know. Also, I'd be interested to hear about results YOU have had with true handheld HF DXing.

M0BMU's latest complete 8.97kHz Portable Receiver

Jim Moritz M0BMU has updated his loop/preamp circuit for 8.97kHz turning it into a complete direct conversion receiver for 8.97kHz. He posted this on the LF reflector in the last few days. I have added this to my sub-9kHz website (scroll down for Jim's description and schematic on the webpage. See http://sites.google.com/site/g3xbmqrp/Home/10khz

Further 8.97kHz DX tests from Germany

DK7FC conducted more tests on 8.97kHz last weekend. Best DX was 300kms mainly because the noise levels are now higher than in the earlier tests. However it allowed Stefan to test some new equipment successfully.

Portable clifftop DXing

No updates for the last week as I was on holiday and out of internet contact. This last week I had a couple of chances to do some handheld SSB DXing with the FT817 from a Devon clifftop near Thurlestone. Although I think I stood a chance working LU2DO last night (I called and called and no-one else seemed to be hearing him), I did manage some European QSOs on 15m (HB9CVQ and a DL) and 6m SSB (IW0HLE) when running just 2.5W to a small whip antenna. I use an 8 foot long dangling wire counterpoise which helps a lot. On 6m I was just using the short helical supplied with the rig and only about 20cms long! Clifftop portable sites are magic with a decent low angle take-off, not that this matters so much with sporadic-E. In the past I've worked South America and the USA with handheld SSB.

13 May 2010

IC7000 reliability

Some people have had issues with the reliability of the IC7000 driver transistor which gets too hot and can self-destruct. SV8YM has some modifications to help, putting improvised heatsinks on the effected devices so they run cooler. See his blog at http://sv8ym.blogspot.com/.  This is a rig I've considered purchasing but I have been concerned about the heat in such a small box and consequential reliability.

New 500kHz beacon in Norway LA1ASK/B

A temporary beacon LA1ASK/B will be operational during May until mid-June from the island of Toftöy near Bergen, Norway (locator JP20LL).  Frequency 509 kHz, mode A1A (CW), transmitter power 5 W to a 35 m vertical antenna. Reports to <post@bergenkringkaster.no> or QSL via the LA Bureau or direct, info at www.la1ask.no

12 May 2010

30m QRP transceiver from GJ7RWT

Andy GJ7RWT has sent me his schematic for a 30m QRP CW transceiver which has some similarity to the XBM80-2 and the transceiver from K4TWJ. He gets 150mW out and the receiver can copy signals down to around 10uV. He has made the circuit on strip board (veroboard) and the layout he used is attached.

Further tests on 1kHz using conduction and induction

Today I continued "by ear" testing local induction and conduction communication using my 4W PA at 1kHz with 10m spaced grounded electrodes. Using the 80cm loop, HPF and audio amp I was able to achieve 0.3kms today, slightly less than on Monday. Everything else is unchanged, so I'm wondering if the effective TX loop area formed by the 2 earth rods in the ground changes with soil moisture? I.e. when the soil is damp is the loop smaller? Logically this makes sense. Copy using my 80cm loop and VLF up-converter was disappointing: I was unable to get further than 0.2km. This system needs further work as this should be every bit as good or better than the audio amp receiver.

Also today I checked the resistance of the TX grounded electrode system using an audio oscillator and potential divider method: it measures approximately 50-60 ohms from 1-10kHz, which is not too bad. I also tried receiving my signal 0.2km away using another pair of grounded electrodes spaced by 10m. Although copy was just possible, the signal was buried in mains hum. Mains hum pick-up on the loop is much lower. This again suggests that the main means of communication is induction, not conduction through the soil.


Stefan DK7FC posted the 300W PA used in his historic tests on 8.97kHz on the LF Reflector today. He's been copied by at least 10 stations in 5 countries using this PA with best DX 902kms.

11 May 2010

4W TX for sub-9kHz experiments

Attached is a picture of the "transmitter" I'm using for my ground and induction communications tests. It uses a TDA2003 audio IC into a toroidal step-up transformer that can match from 10 to 150 ohms. Not sure of the transformer type which came from an old Pye Telecom PMR radio, possibly an M206, Whitehall or similar (it was used on the audio stages). I haven't yet tried listening with an active probe antenna to see how that would perform. Time is limited, so further tests may have to wait until the end of the month. Best range so far, receiving "by ear" on a loop antenna, with no clever selectivity or signal processing, is 0.35km.

VLF loop and up-converter ready for tests

This is a shot of my receiving loop antenna for sub-9kHz local earth-mode and induction comms testing. The loop consists of 30 turns of wire on a wooden frame. This feeds into my SBL1 based VLF-to-HF up-converter (the small blue box on the frame). The output of the converter feeds into the FT817 receiver.

10 May 2010

Japanese Hamsat off to Venus

On May 17 Japan's Space Agency plans to launch a mission to Venus. It will also be carrying a 35cm cubed nano-satellite developed by universities and colleges. This nano-satellite will go into a Venus encounter trajectory and will become the world first university satellite which goes beyond the moon. It will perform technology experiments and test long-range, inter-planetary communication using amateur radio frequencies:
Downlink Frequency: 5840.000MHz, band width 20MHz
Transmission Power: 4.8W/antenna, 9.6W total
Antenna: 2 Microstrip patch antennas
Modulation: AFSK/FM 1200bps during LEO flight
CW 1bps during Interplanetary flight

DK7FC's 8.97kHz VLF grabber active antenna

DK7FC runs a grabber on 8.97kHz so he can monitor signals testing on this VLF frequency. He feeds the signal from this active antenna into his PC's soundcard. This is a sketch of the schematic that Stefan posted on the LF reflector today. He has since added some additional C between the drain and ground to reduce the intermod products from LW/MW broadcasters that otherwise produce a strong line on 9kHz.

VLF up-converters and MOSFETs

Today I built a MOSFET up-converter, converting 7-9kHz VLF to around 20MHz. However, I was disappointed with the results: low conversion gain and sensitivity when using either a 3N211 and a BF981 device. I used an 82mH choke with a 4n7 cap as the tuned circuit on G1 (tapped capacitance for max sensitivity with 50 ohm input) with LO injection on G2. Despite optimising everything I couldn't better the sensitivity achieved with the SBL1 based up-converter that appears on my website.

Filter Calculator (and other calculators)

When designing a simple Sallen-Key active filter yesterday for my VLF receiver I found several useful web resources. One of the best is http://www.calculatoredge.com/index.htm#electronics that has a lot of useful calculators for electronics. I like the fact that when designing filters it asks you, and gives you, values in "real" numbers like nF and kohms. Some calculators ask you to give values in Farads and ohms to the power E-09 and similar and are obviously written by a college professor and not a real engineer who finds it hard to work these out!

9 May 2010

Sub-9kHz NoV - still awaiting Met Office OK

I chased Rod at OFCOM this weekend to see if there was any further news on the NoV application to TX below 9kHz. The hold-up is still the Met Office, from whom OFCOM are awaiting approval. I'm carrying on with sub-9kHz earth-mode and induction tests at 4W meanwhile as I can't imagine anyone will object. My transmissions last about 10 minutes and the radiated power is picowatts!

Earth mode and induction testing at 1kHz

Today I restarted my earth-mode and induction communication tests at VLF using with my 4W transmitter and 10m separated earth electrodes. After some false starts, I ended up by field testing a simple receiver consisting of 30t of wire 80cms square into an active high pass filter followed by 3 stages of audio gain into a crystal earpiece. 2N3904 transistors were used at each stage. With the loop over my shoulder I set the TX sending 1 second "beeps" at 1kHz and went walking....

Even with 20-30dB of 50Hz rejection it was still an issue in many places. Walking across the field behind my house, and well away from cables and pipes, the signal could be heard in the earpiece at RS53 to a distance of 0.35km. Mains hum and LW/MW interference (the RX is not in a screened box) rather than signal level  limited further range. This week I'll add more high pass filtering, put the RX in a screened box and make the whole thing more immune from BC breakthrough. As I can hear this signal by ear at 0.35km with essentially no narrow filtering, then I'm confident that twice as far will be possible with QRSS/WSPR and a PC based receiver. Not bad for 4W at 1kHz.

10m Es

Put the 10m QRP WSPR beacon on early today and already there are spots from the G, CT and OY. The sporadic-E season is gathering pace.

8 May 2010

The Spirit Level - a book I recommend

"The Spirit Level" is a book by Richard Wilkinson and Kate Pickett published in the UK by Penguin showing hard evidence that almost everything - from life expectancy to mental illness, violence to illiteracy - is affected not by how wealthy a society is, but by how equal it is. Societies with a bigger gap between rich and poor are bad for everyone in them, including the well-off. It is a book full of positive solutions and shows how we can move towards a happier and fairer future.

7 May 2010

The Limerick Sudden receiver kit

The GQRP club has launched a new kit called the Limerick Sudden. This was the message from George G3RJV today on the GQRP Yahoo Group:
"Limerick Construction is an exciting new way of construction. Conceived by Rex Harper, W1REX, of Limerick Maine it offers a simple and attractive way of building equipment. Based upon the Manhattan construction method (surface mounted parts on insulated pads) it also lends itself to the production of easy to build kits.

For some months G3RJV, G3MFJ and W1REX have been looking into producing a basic receiver kit in Limerick format. The resultant project, based on the G3RJV Sudden is now available in kit form. See http://www.gqrp.com/sudden.htm . It is complete in every way ... all parts... board ...case...no coils to wind ... even a battery! We hope members will enjoy our new Club Sales offering. "

Shoe power source (from Elector Newsletter)

A novel way of generating a small amount of power using a piezo-electric generator within a pair of shoes is shown in the latest Elector Newsletter.

6 May 2010

Useful Simple Signal Generator

Dom Baines has a useful blogsite and today I noticed this NorCal circuit on his page for a multi-band S9/S1 signal generator. It uses a switched crystal oscillator with 2 well-defined output levels at 50uV and 1uV, so is ideal to test receivers.

More VLF DX TX tests by DK7FC planned

Stefan DK7FC is applying for permission from the German authorities to erect a 300m long kit supported antenna for his next transmitting tests on VLF. Before this is possible he hopes to test with a 200m long kite antenna. The main concern now is summer noise levels on VLF and the effect this will have on DX possibilities. Some ionospheric propagation simulations by SQ7MPJ suggest that attenuation over an 800kms+ distance would be a few dB less if the TX frequency was reduced to around 5-6kHz instead of 8.97kHz because of the effect of the D-layer.

OY1OF on 10m WSPR - Doppler shifted

OY1OF was already receiving signals from me and G3ZJO at 0724z today on 10m WSPR. His signal with me had very distinct Doppler shift on each transmission suggesting that the E layer is moving or at least is unstable. The sunspot count (unrelated to Es I think) was at a very high 77 today. I've now reduced my TX power back to 1W as 5W is probably too much. I must try WSPRing on 10m with very low mW levels soon.

5 May 2010

My shack in 1977

Thumbing through some old family photos in a box tonight, I found this one of my shack as it was in 1977 when my son was about 1.5yrs old.  It was interesting to see what gear I had then. On the far right  of the table is the Liner-2 144MHz 10W pep SSB transceiver. Next to it is a 28MHz 1W crystal controlled CW TX (xtals on the log book) and below that I think it was a 15W PA for 28MHz that I used briefly. On the left of this is the Eddystone EC10 receiver which was used with a down converter to RX on 28MHz. I had more space then than now!

The Heathkit Lunchbox on 75m AM

K6KWQ has just built a Small Wonders Lab "Retro-75" QRP AM transceiver kit into an old Heathkit HW30 (Lunchbox) case. The Retro-75 puts out 2.5W AM on 80/75m and is a nice way of getting back on AM on the band. AM is quite popular in the UK with stations active around 3615kHz.  Dick has made a very neat job of re-labelling the old Heathkit box so it looks like a genuine Heathkit rig, but for 75m AM.

4 May 2010

Photo of a man born in 1746

Looking through my old photos I found this today. This appeared in a newspaper some years ago and it shows a man who was 102yrs old when the photo was taken in 1848. This means he was born in 1746, 10 years before Mozart was born and was a middle aged man when the Bastille was stormed in Paris. The calotype photo was taken by William Collie who I believe was a photographer on Jersey in the Channel Islands. See also http://www.all-art.org/history658_photography5-2.html

Sunspot count 61

Although conditions have been a bit disturbed lately, the sunspot count reached 61 today. This is a decent sunspot number and conditions are certainly on a generally upward trend now. This autumn should see conditions very much better on the higher bands than for many years. Whoopee!

3 May 2010

10m WSPR - real DX

Here's a shot of the shack since it's been repainted. All is back in place and I've just been rewarded with a WSPR report from CX2ABP at 11127kms by F2 TEP mode when running 5W to my 10m wire halo Homebase-10 antenna. I wonder if this is a combination of Es and F2 TEP as I'm also getting WSPR spots from Spain.

10m WSPR - interesting short skip

This morning and lunchtime I've been running 5W WSPR on 28MHz. There was some Es propagation but the most interesting reports were from Holland with two reports at around 450kms. Now this is usually too short for Es propagation, so I wonder if this was tropo?

2 May 2010

8.97kHz noise levels

DK7FC has delayed further DX tests on 8.97kHz because of thunderstorms in Germany. Stefan comments that the noise levels appear to be rising as thunderstorm activity increases as we move towards summer. He is wondering if further VLF DX tests should be postponed until the autumn when the noise will lower again. You can check UK thunderstorm activity on the Nowcast website.

QRP AM TX for 12m or 10m (ON6MU)

Just spotted this little circuit on ON6MU's website: it's a small 100mW QRP AM transmitter for either 12m or 10m using a single stage modulated crystal oscillator. AM can be quite a lot of fun on 10m around 29-29.1MHz.

Back on the air and 10m Es

This evening I finished repainting the bedroom shack and got all the radio gear back in place. Connecting the antennas I noticed sporadic-E on 10m this evening with a CN8 audible on SSB: the Es season's started, so I'll be looking out for some QRP DX on both 10m and 6m. As mentioned before, I'll be using WSPR on 6m when not active but in the house.