If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #43294
Joined: Mon Feb 24 2014, 06:40PM
Location: Near Walsall in the UK
Posts: 11
Paul Nicholson wrote ... There are no amateur radio allocations below 9kHz but in some countries you are allowed to transmit. In the UK you need a 'Notice of Variation' to your licence.
I enquired as to the standing of this area of experimentation in the UK with OFCOM. The response was as you said, you need an NOV.
Also I was told that no portable operation was allowed. The NOV I was informed might not be issued at all even if OFCOM was supplied with the fullest info that they requested. If the NOV was granted it would be for an initial period of 6 months and then would be reviewed, but they would offer no guarantee of renewal.
The main 'user' in the UK I was informed was the Met Office. They apparently monitor lightening down there.
OFCOM were concerned that my small battery powered audio oscillator fed into two metal tent pegs in our back lawn would interfere with reception of 10+ megawatt lightening discharges...
Registered Member #47220
Joined: Fri May 30 2014, 12:20AM
Location:
Posts: 4
Does polarisation matter?
Yes, only vertical polarisation will propagate more than 100km or so. The other polarisation is strongly attenuated.
Surely what's good for the transmitter is also good for the receiver? Or is it the case that environmental noise exceeds practical device noise, so antenna/LNA matching is moot?
Natural radio noise comfortably exceeds the typical device noise floor, although to ensure this, you need to make sure that the front end device is chosen appropriately for best noise match with the antenna impedance. That's down to having the right ratio between device voltage noise and current noise. op-amps work well, eg AD823 for high impedance E-field probe and LT1028 for low impedance magnetic loop.
I can't imagine the vertical that would not create lots of corona with 240 kVrms at 9 kHz
Would be quite difficult to cope with on a wire antenna. Amateurs are using up to about 30kV on the wire and tend not to use corona rings, etc. Higher voltages ought to be possible, especially by the HV and Tesla experts on this forum.
The NOV I was informed might not be issued at all even if OFCOM was supplied with the fullest info that they requested. If the NOV was granted it would be for an initial period of 6 months and then would be reviewed, but they would offer no guarantee of renewal.
That about sums up the NoV situation. Only about three UK amateurs have followed that process. It is much easier in Europe and there are several active stations. Yes the Met Office are the main VLF user in the UK and there are a few university VLF receivers used for research. OFCOM are obviously concerned to protect those operations. In Germany, VLF is also used for weather tracking, in the band 8.3 to 9kHz and amateurs operate below 8.3 kHz because of this.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
What about folks who set up electric fences? Would these not be a significant noise source, as most of these use fairly high loss (eg wood) poles to support the HV ropes and no doubt a significant amount of power leaks into the ground in this way.
Registered Member #43294
Joined: Mon Feb 24 2014, 06:40PM
Location: Near Walsall in the UK
Posts: 11
Conundrum wrote ...
What about folks who set up electric fences? Would these not be a significant noise source, as most of these use fairly high loss (eg wood) poles to support the HV ropes and no doubt a significant amount of power leaks into the ground in this way.
If the radiation is incidental, or accidental, very often a blind eye is turned towards it (unless major interference were to result).
Most of the VLF/ULF systems I have seen over the years have antennas that are so inefficient you would be lucky to get anything from them at all.
It would be quite easy for the 'powers that be' in the UK to allocate a spot frequency for Hams to experiment sub-9khz, and that way all of the lightening monitors would know what to ignore (how difficult is it to set up a DSP notch filter in this day and age?)
By the way, a very good source for ideas and designs for low frequency reception can be found at www.vlf.it
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
High voltage amateur radio - VLF
