|To:||"[email protected]" <[email protected]>|
|Subject:||Re: [EXTERNAL EMAIL] Re: VLF: GOTA|
|From:||David Hine <[email protected]>|
|Date:||Fri, 11 Jan 2019 18:05:25 +0000 (UTC)|
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Hi Paul R.,
My objection was the proposed (GOTA) infrastructure use, such as motorway guards, fences, railway lines etc., and pylon towers as makeshift VLF antennas. This has the potential to upset signalling, and other infrastructure communications, as well as placing wires
and other 'junk' that could also prove a physical hazard. Such activity is strictly illegal, and will lead to a jail sentence if caught on camera. That must be far more important than radio experiments that won't work anyway.
My Wikipedia Project Sanguine reference was adequate for purpose here, and shows how inefficient these obsolete ELF TX antennas really are.
As you know, VLF TX antennas must be vertical polarised -that is vertical masts to be able to radiate a signal, and these have to be
around 1000 feet high to launch a VLF signal effectively. A low horizontal structure at ELF / VLF would have dismally low efficiency, no
better than a wire Beverage VLF receiving antenna, and that's why I mentioned the Beverage.
Anyway, the main point is never be tempted to use any utility structure (including metal bridges) as any sort of radio antenna.
If you still disagree with my post, ask what the RSGB or Ofcom thinks of this, and report back here their reply.
From: REEVES Paul <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Friday, 11 January 2019, 10:56
Subject: RE: [EXTERNAL EMAIL] Re: VLF: GOTA
Several points of contention here – your description of Project sanguine is incorrect in some details (but you can blame Wikipedia for that). It was, in fact, rather like the antenna you so strongly object to. I would suggest you obtain a copy of ‘ELF Communications Antennas’ by Burrows. It is a bit dated now but is a good beginners text.
While VLF antennas tend towards vertical polarisation (I note you change from ELF to VLF here….) vertical polarisation is not a specific requirement for propagation but does make a rather more easily constructed (relatively compact) antenna for the frequencies concerned. I would also disagree with your description of the Beverage but why introduce it?
Discussion about whether or not to connect to infrastructure belonging to other entities is another matter entirely.
My background, by the way, is in antenna and comms system design for submarine systems so feel free to ignore me – I have a rather narrow viewpoint!
Hi Neil, Then only published info that I'm aware of is the ELF antenna used by the USA to transmit ELF signals on 76 Hz to submarines. This was 'Project Sanguine'. It used about 15 miles of power cable suspended on 30 foot poles above ground and was earthed at each
end. A TX of around 5 Megawatts, about half way along this cable supplied the 76 Hz at a few hundred Amps. The radiated power was around 3 Watts, and was just sufficient to travel the globe. Project Sanguine was abandoned some years ago, as it fell obsolete as new sophisticated comms replaced it, such as satellites etc.. It was very expensive, only one way comms, and the 15 mile of cable was constantly being attacked by vandals and metal thieves. Russia still uses a similar system on 82 Hz (Zevs), and they shoot to kill anyone tampering with their cable!!!
There is an excellent Wikipedia page on Project Sanguine. Basically, it was a very inefficient monster narrow loop.
Otherwise, conventional Marconi vertical masts tuned against ground are used for VLF TX'ing the vertically polarised signals, at any
VLF frequency up to the LW broadcasting band.
From my experience, long low metal structures of any kind do not make good VLF / ELF TX antennas, and for that reason are never employed.
Also, they do not generate a vertically polarised signal, which is very necessary for VLF and ELF propagation. The historic 'Beverage' type of horizontal wire antenna is long, but only suitable for reception (very inefficient as a TX antenna).
Vertical balloon suspended wires do work, but you must observe the maximum height restrictions allowed in any particular location.
I hope this is useful.
Kind regards, David
This sounds interesting. Can you point at any published results to explain what technique was used, what power was used to obtain those results, and how the signal was launched? I imagine lots of people are considering the use of long lengths of metal infrastructure (on private land, with the express permission of the landowner), so if there is a solution which is demonstrably better, it would save a lot of unnecessary trouble for experimenters.
Do you have any numbers comparing the technique used in these experiments against those obtained from using long lengths of armco or metal fencing or huge bridges, (putting aside any arguments about the rights and wrongs). It would be good to see a documented comparison to show by what margin the experimental technique used is superior to using low steel structures with a large horizontal extent.
On 10/01/2019 18:37, David Hine wrote:
... TX connexions to motorway
guard rails, railway infrastructure, electric / gas supply utilities and fences etc. are totally unnecessary for the transmitting of ELF
These DO NOT make good VLF / ELF TX antennas ..
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