One for Kelly, Mike et al - Radio Communications.

Lol the similarities are striking I wonder if they ran there own radio station maybe something like cave FM  or radio Flintstone makes you wonder doesn't it??

And indeed the company I work for, once long ago part of the Plessey group, sometimes makes and installs something very like the monopoles on the outside ring of that photo.   We do joke about stone age technology, but that is not what we mean...

Which in turn looks very like this sort of thing   

Portable, well luggable, versions exist for those sunnier "holiday destinations"

Mapj1 that is an impressive system I had no idea so much use was made of HF radio for commercial purposes  I have heard some data signals just to the edge of the broadcast bands  it's amazing what goes on out there

The RAF certainly had both ground and airbourne HF direction finding capabilities. Also VHF and UHF down to airfield control towers.


I assume this capability is retained in one of these, but that is just I guess. 

https://www.raf.mod.uk/aircraft/airseeker-rc-135w-rivet-joint/

I remembered that a radio navigation aid fitted to a lot of aircraft is known as Non Directional Beacon (NDB). A LF radio signal is transmitted from airfields and airports in morse and aircraft have a receiver when tuned to the required beacon gives directional information on a cockpit instrument. I tuned up my nearest airport which is London City on 322kHz and heard LCY pumping out in morse.

Near many centres of population in the UK the HF band is quite badly jammed by leakage from telephone lines carrying ADSL and VDSL , and in many houses also from poorly suppressed electronics such as electronic transformers or LED lights etc.. As the 'DSLs in particular sound quite noise like to the untrained ear, it is often mistakenly assumed that HF is unused, and that  the noise floor is very high. (For those so equipped, specialist software, Lelantos, is available that can automatically  distinguish VDSL noise from other sources, but it is not a trivial thing to set up, and requires the right sort of digitising receiver.)

As you get further out of town and away from the Open Reach wide area jamming networks, the noise falls away and you realise that at the sub microvolt per metre E field level it was indeed quite busy out there, and there are lots of interesting things going on, not just local Amateurs and a few  really loud broadcasters like Voice of America or China Radio International and Radio Taiwan trying to drown each other out.

If you are ever lucky enough to have a HF directional array at your disposal that does elevation and Azimuth is quite fun to see what you can pull out from under the noise coming in from the quiet directions and indeed also sobering  to see where the noise is coming from and how much of it there is too.

Hopefully if broadband moves to using fibre to the house this will clean things up in the coming years.

Using rings of antennas with an antenna at the middle,  and  combining the signals with the right phases and amplitudes to allow the user to select (or null out) a  signal  from a particular direction receive . This is 'old hat'.

A wide band coherent receive chain and high data rate digitisation and storage on each antenna allows recording, and then potentially many hours after some event, the recorded signals can be re-combined with some desired  amplitude and phase to look at arbitrary signals of interest from one or more a specific directions.  This is the 21st century  game changer, as you can in effect go back and listen to something over again, but concentrating on (or removing) signals from a different angle.

There seems to be a selection of antennas on the top of the doughnut https://www.historytoday.com/sites/default/files/GCHQ-2_0.jpg 

I wonder what is inside? The same could be said for my receiving antenna http://ancient-mariner.co.uk/public/2008.08.28%20Antenna.jpg ?

Clive

Clive


What is that drain pipe looking thing outside your house? What type of Rx is it connected to? Can you use it to transmit?

John

The business end is an e-probe antenna designed by Roelof Baker PA0RDT which covers from 10 kHz to HF. A good set of photos is at https://www.merseyradar.co.uk/uncategorized/hf-receiving-antenna-pa0rdt-mini-whip/   I bought mine - a bnc version - direct from Roelof some years ago. After a good rub down with glass paper! It is at the top of the pipe, sitting on a length of 20mm uPVC conduit.  The Receiver is a RF-SPACE SDR-IQ again about 15 years old and sadly now discontinued (I believe one of the ic/s became unobtainable). This rx only has three connects, a bnc aerial i/p a USB and a 9-pin which is used for external receiver control to tap-off from the IF. In turn, the SDR-IQ connects to a  Silex SX-2000U2 USB network adapter connected to a network switch in the room the other side of the wall. My pc has a program SpectraVue http://rfspace.com/RFSPACE/SpectraVue.html which in the case of an SDR-IQ, lets me observe or record a 190 kHz spectrum. Demodulation is  carried out within the software. The reason for external receiver control is to use an SDR-IQ as a panoramic adaptor.


My interests tend to be VLF/LF.


The only problem I have had is capacitor failure in the linear 5v psu - switch mode psu's often being being noisy.


As an aside, one morning I thought that I had discovered a new, unknown VLF transmission. A rock steady signal pulsing on and off in a regular manner a couple of times a minute.  Got excited and went into our kitchen to hear the washing machine in action in our utility room. Washing over, so was my "new" station...


On VLF, I am a follower of Grimeton Radio/SAQ This is their CW Morse message on 1st July 2018 on 17.2 kHz from a high frequency alternator.
http://ancient-mariner.co.uk/public/2018.07.01%20-%20SAQ%20Alexanderson%20Day.bmp


Here is a screen shot of the leap second on 31st December 2016 http://ancient-mariner.co.uk/public/2016.12.31%20-%2023-59-60%20Leap%20Second.pdf  SpectraVue is showing the 60 kHz time signal from Anthorn and the window on the left is showing the UTC time as 23:59:60  which was the leap-second.  This is from my Trimble 10 MHz GPS frequency standard, now neatly cased

 http://ancient-mariner.co.uk/public/IMG_1364.JPG rather than wires all over my bench.

Sadly due GPS rollover, that piece of software now shows the wrong date, but the 10 MHz is fine. There is other software which corrects the outputted data. Trimble "meanly" decided not to supply updated firmware.


Besides QRM from VDSL, I am about 250 metres from 132 kV overheads, so reception not too bad.  I have never seriously tried the above combination on HF, must get round to it.


So, no good for transmitting!


You can get PA0RDT mini-whip kits, but I have one where the circuitry had either been strangely modded, or something had gone wrong when laying out the pcb tracks.. The actual metalic antenna, is about the size of a large postage stamp.

73's Clive