Low Frequency Radio Transmission

Can you provide explicit instructions as to what to do with the length of wire?


Andy Betteridge

As much of it spread as wide as poss as far away from terra firma as possible, and away from sources of interference like power lines, VDSL lines etc.

Over some trees is good. You have no chance of getting a resonant length at these freqs so just try and get some tens of metres out there.


The alternative is to try a tuned loop, to get the H field rather than the E. Still needs to scoop up several square metres.

Presumably there has to be some sort of connection from the wire strung over your garden and the sound card.


Remember that when I was a kid we had such a length of wire from the house to an oak tree attached to the valve radio to improve the reception of Radio Luxembourg and the pirate stations, so I have done that bit, as well as setting up a CB radio stick antennae on top of a length of steel pipe with a ground plane using a SWR meter, so have done that side of it.


Andy Betteridge

and crystal sets, as well as Jamboree On The Air with borrowed short wave gear.


But I cannot say I have kept up with it and gone beyond the very basic stuff since then and it feels like a long time ago.


Andy B.

a germanium diode OA91 if memory services,  a variable cap, long high bits of wire (as kids we scrounged odds and sods of wire).earth was a wire wrapped around a water pipe and high impedance headphones or a crystal earphone.No battery required.  Radio 4 (The Home service) . Happy days.


Yes do you connect your antenna to the sound card? how? cap coupling with ali foil?

I would hazard a guess at a fairly high value cap (due to the low frequency) to the mic input? but the demodulation... is that done in software or hardware, enquiring minds!

For this transmission you do not need the diode - it is not AM on a supersonic frequency like the home service would have been.


As a historical aside.

During the war the many regional transmitters were given common central programme content, and all retuned to transmit on one of two frequencies (to confuse any enemy use of radio direction finding) 668kHz (South chain) and 767 kHz (North chain), later augmented by fill in transmitters ("Group H") 1.474 MHz.

1967, the BBC split the Light Programme into a pop music and entertainment network. The Light Programme became BBC Radio 1 and BBC Radio 2 long wave. The BBC Third Programme became BBC Radio 3,  Home Service was renamed BBC Radio 4.

In 1978  radio 4 moved to a longwave channel  on 198khz, and radio 2 moved back to medium wave.

The easiest to receive on a crystal set would be longwave and the longer end of the medium wave.

This transmission is  quite different,  being at a frequency so low 17kHz, that it can be fed directly into the microphone input to a soundcard, after all, it is generated by a rotating genset, not a valve in sight..

Connect one end of the wire, any insulated wire, to the centre pin tag of a 3.5mm jack plug. Via a capacitor if you wish, a 1.8µF capacitor as can be found in a BT master-socket etc should be ok. Plug into the Mic input of the pc or laptop. Try and get the wire up as high as you can, or say from an upstairs window to a shed roof or similar.


I found that with the SAQrx program running, but without the wire connected, whistling into the built in Microphone will produce activity on the screen.  Once the wire is connected, there are other Very Low Frequency signals around which you should see on the screen. Most of these are phase-shift keying, just a warbling noise, but there is a Russian station which sends Morse using frequency shift keying. Which even to a professional ear is not easy.


I use a high impedance e-probe as an aerial. The actual aerial being a piece of copper foil about the size of a standard UK postage stamp. This has two transistors, one to impedance match the other to drive the coax cable to the receiver which is a Software Defined Receiver, an SDR-IQ manufactured by RF-Space which I bought from the USA about 13 years ago and associated software which gives me a spectrum of the range of frequencies that I am "looking" at.
http://ancient-mariner.co.uk/public/2018.07.01%20-%20SAQ%20Alexanderson%20Day.bmp  You can see the Morse code running vertically beneath 17.2 kHz and at 60.0 kHz The UK MSF radio time-signal and similarly at 77.5 kHz the German DCF77 radio time signal. Either of these are used by radio controlled clocks and watches to maintain an accurate time display.   The other transmissions are all naval. (VLF penetrates water, LF less so; say no more!)

I did actually think, do you just connect the long piece of wire to a jack plug and insert it into the microphone socket.


Then I thought that just sounds too easy and refrained from saying it out loud ?


Andy Betteridge

A nice interference and static free signal on 17.2 kHz this morning at 08:00 utc giving nice easy copy.

CQ de SAQ SAQ SAQ =
THIS IS GRIMETON RADIO/SAQ IN A TRANSMISSION USING THE ALEXANDERSON 200 KW ALTERNATOR ON 17.2 kHz.


WE WISH YOU ALL A MERRY CHRISTMAS AND A HAPPY NEW YEAR.

= 
SIGNED: THE WORLD HERITAGE AT GRIMETON AND THE ALEXANDER-GRIMETON VETERANRADIOS VAENNER ASSOCIATION +

FOR QSL INFO PLEASE READ OUR WEBSITE: WWW.ALEXANDER.N.SE

= DE SAQ SAQ SAQ VA  


Clive