Peter, Why load it and try to feed it as a current fed extremely short aerial.
Would it be easier to calculate a parallel tuned circuit and feed it off the
top....voltage feed. You could then use a much smaller inductance and a few
farads and have a very narrow bandwidth. The efficiency would still be minute
but the firework display after dark would be a wonder to behold! :-)) a later
day Tesla.....
Actually you would get a much "bigger" aerial by putting two stakes in the
ground. This gives a loop because the skin depth at these freqencies can be 10s
of metres probably more than the height of your inv "L". It is also easier to
feed via a transformer like a loop. (from the book I referenced)
Alan G3NYK
--- On Mon, 22/2/10, M0FMT <[email protected]> wrote:
> From: M0FMT <[email protected]>
> Subject: RE: LF: VLF_8.79 kHz
> To: [email protected]
> Date: Monday, 22 February, 2010, 22:43
>
> Yep Rik
>
> So how do I load it?
>
> I agree there is about 780 Watts being disapated in
> the coil so it would act like a one bar electric fire while
> the wire held out before melting.
>
> I have other options of about 400 watts, 250 Watts and
> about 100 Watts of audio to try out.
>
> I need a plan that does not contain unobtainum like
> most of the RSGB designs in the LF Handbook.
>
> I want to use an air core transformer if at all
> possible....... there is a lot of pontificating on
> this reflector about this subject but I am looking
> for a practical method of loading a wire antenna and need
> help, ideas-wise.
>
> If I can load it with any of the power levels
> above there are LF stations who may cooperate in
> doing an RX test like G7NKS about 6.5 km away possibly
> G3xiz or M0jxm roughly 10km away.
>
> May be trying to load a piece of wire, which is a
> miniscule fraction of a wave length, in the
> conventional way is not the answer.
>
> So I am open to ideas (practical ones)......
> anyone??
>
> 73 es GL petefmt
>
> --- On Mon, 22/2/10, Rik Strobbe
> <[email protected]> wrote:
>
>
> From: Rik Strobbe <[email protected]>
> Subject: RE: LF: VLF_8.79 kHz
> To: "[email protected]"
> <[email protected]>
> Date: Monday, 22 February, 2010, 21:24
>
>
>
>
>
> Pete,
>
> 2.5km Cu wire
> of 0.2mm has a resistance of 1345 Ohm.
> So even if the
> coil doen't get hot by the HV it certainly will by the
> dissipated power.
>
> 73, Rik
> ON7YD - OR7T
>
>
>
> Van:
> [email protected]
> [[email protected]] namens M0FMT
> [[email protected]]
> Verzonden: maandag 22 februari 2010 19:19
> Aan: [email protected]
> Onderwerp: RE: LF: VLF_8.79 kHz
>
>
>
>
>
>
>
>
>
> Hi Group
>
> Using software to calculate what I would need to load
> my inv "L" on 8.9 kc/s with my 8 Ohm
> O/P 800 Watt audio amp I get :-
> A coil/transformer of about 1 Henry which with my air
> cored former is 1400 turns,
> 2.5 km length, of 0.2mm diameter wire.
> A coupling loop of about 2 turns.
> Creating an antenna current of about 1 amp being
> driven by about 60kVolts. Making a coil that will be
> getting pretty hot!!!!! Probably red hot.
> Any suggestions??
>
>
>
>
> 73 es GL petefmt
>
> --- On Mon, 22/2/10, James Cowburn
> <[email protected]> wrote:
>
>
> From: James Cowburn <[email protected]>
> Subject: RE: LF: VLF_8.79 kHz
> To: [email protected]
> Date: Monday, 22 February, 2010, 16:31
>
>
> All we need is a wire strung between
> K2 and Everest summits and fed from
> base camp below?
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]
> On Behalf Of Warren Ziegler
> Sent: 22 February 2010 16:23
> To: [email protected]
> Subject: Re: LF: VLF_8.79 kHz
>
> No license is required in the US below 9kHz.
>
> I agree with Mal its very difficult to radiate a signal on
> 137kHz, let
> alone 9kHz!
> --
> 73 Warren K2ORS
>
> WD2XGJ
>
> WD2XSH/23
>
> WE2XEB/2
>
> WE2XGR/1
>
>
>
> On Mon, Feb 22, 2010 at 11:10 AM, ALAN MELIA <[email protected]>
> wrote:
> > Hi as far as the Uk is concerned it is not allowed.
> You probably need to
> contact Andy G4JNT for details he did approach the
> regulator at one time
> maybe around 2001/2 when Geri was doing his tests the
> answer as I remember
> was:-
> > Frequencies below 10kHz are not allocated by
> International Treaty but we
> control all frequencies between DC and gamma rays, and no
> we will not be
> issuing any licences for that region.
> >
> > I believe that was the RadioCommunications Agency
> things may be different
> now
> with Ofcomm. The best person to know whether an approach
> would be
> worthwhile would be John Gould G4WKL who nursed the 500k
> stuff through.
> >
> > Alan G3NYK
> >
> > --- On Mon, 22/2/10, Stefan_Schäfer
> <[email protected]>
> wrote:
> >
> >> From: Stefan_Schäfer <[email protected]>
> >> Subject: LF: VLF_8.79 kHz
> >> To: [email protected]
> >> Date: Monday, 22 February, 2010,
> 11:32
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> Ok Roger,
> >>
> >>
> >>
> >> And do you know if f<9kHz is free for other
> countries in
> >> europe as
> >> well? What about the UK?
> >>
> >>
> >>
> >> If such a grounded dipole is best, than it is easy
> to build
> >> a big
> >> antenna without the problems we have on LF
> (getting the
> >> wire high above
> >> ground). So we also could try big/long antennas.
> Waht do
> >> you mean with
> >> amateur levels? Power range is clear, something
> arround
> >> 500W+-6dB. But
> >> the antenna? Sure, if you think about building an
> antenna
> >> in the
> >> garden, say 2x20m, is not very effective but what
> about
> >> 2x500m in a
> >> forrest, perhaps with the loading coils (which
> will be on a
> >>
> ferrite
> >> toroid i think) mounted 300m apart from the
> center? That
> >> could be
> >> interesting and easy to try. No tower, no earth
> radials,
> >> just 2 wires
> >> hung up on some trees and measured the impedance
> at the
> >> feed point,
> >> that would be a first step.
> >>
> >> This antenna will still be bad but what we are
> doing -on LF
> >> it is the
> >> same- is beeing fascinated to reach a good
> distance and
> >> make some
> >> contacts at very low frequencies, although it
> would be much
> >> easier on
> >> 40/80m...
> >>
> >> And so, if one would reach 50km with such a short
> dipole,
> >> the
> >> fascination would be enormous, isn't it? ;-)
> >>
> >>
> >>
> >> Has anyone, except Horst, tried such experiments
> as well?
> >>
> >>
> >>
> >> With the ground wave,
> one could reach the whole europe, i
> >> expect. But
> >> that are dreams...
> >>
> >>
> >>
> >> Stefan/DK7FC
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> Am 22.02.2010 11:03, schrieb Roger Lapthorn:
> >>
> >> At this frequency, widely
> spaced, grounded
> >> electrode pairs are
> >> probably the best "antenna". There
> are
> >> references to how these work in
> >> the literature (for example NATO AGAARD papers
> from the
> >> 1960s,
> >> available on the internet I believe) and on one of
> the
> >> German ham sites
> >> (DK8KW) - see http://www.qru.de/#vlf ;.
> >>
> >> Don't expect great ranges: up to 10kms
> is a fair
> >> aim with modern
> >> signal
> processing technology and reasonable (amateur
> >> levels) available
> >> power. Project Sanguine achieved worldwide
> coverage to
> >> submarines at
> >> 76Hz (yes Hertz!) but used enormous power and
> antennas
> >> stretching for
> >> 100s of kms.
> >>
> >> 73s
> >> Roger G3XBM
> >>
> >>
> >>
> >>
> >>
> >> 2010/2/22 Stefan Schäfer
> >> <[email protected]>
> >>
> >> Hello Horst,
> >>
> >>
> >>
> >> That sounds really nice. If it would be easy to
> find some
> >> motivated OMs
> >> in the near field (31km) ;-), that would be an
> interesting
> >> field to
> >> test.
> >>
> >>
> >>
> >>
> Yesterday i have thought about possible antenna
> >> configurations for that
> >> range and got the idea that one could use a
> forrest as an
> >> antenna
> >> tower. There, you could hang up 100s meters of
> wire, in
> >> series and in
> >> parallel. You do not need to have that area beside
> your
> >> house. Nobody
> >> will see the wire and nobody will care about it.
> >>
> >> Since summer 2007 i have a horizontal loop antenna
> mounted
> >> in some
> >> trees on my hill with excellent results on all HF
> bands and
> >> also 160m.
> >> The loop has 130m and is mounted up to 12m above
> ground.
> >> Perfect
> >> matching from 160m to 10m with my symmetric tuner.
> I even
> >> tried
> >> matching on 2200m without a problem but with bad
> ODX
> >> results, of
> >> course. But if one would try 2x 10*100m on VLF,
> the ODX
> >>
> would be
> >> interesting...
> >>
> >>
> >>
> >> JO30OT is abt 160km from JN49IS and thus a little
> far i
> >> think ;-)
> >>
> >>
> >>
> >> What is your RX antenna and have you already
> catched some
> >> commercial
> >> VLF stations in that range? Are there some?
> >>
> >>
> >>
> >> 73, Stefan
> >>
> >>
> >>
> >> PS: One can be sure that there will never be SSB
> operation
> >> ;-)
> >>
> >>
> >>
> >> ________________________________
> >>
> >>
> >>
> >> Von: [email protected]
> >> im Auftrag von Horst Stöcker
> >>
> >>
> >> Gesendet: Mo 22.02.2010 09:29
> >>
> >>
> An: [email protected]
> >>
> >>
> >> Betreff: RE: LF: AW: Beaconing on 8.79 kHz in
> QRSS
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> Hallo Stefan,
> >>
> >>
> >>
> >> there was a notice in Funkamateur 12/05, S. 1287,
> that in
> >> DL the range
> >> <9kHz is free.
> >>
> >>
> >>
> >> I could not believe that so I asked the BNetzA and
> after a
> >> while I got
> >> a letter which confirmed that.
> >>
> >>
> >>
> >> So there nothing you've got to do for getting
> a
> >> licence. You do not
> >> need one.
> >>
> >>
> >>
> >> There is no limitation of technical parameters
> like
> >> bandwith or
> power.
> >>
> >>
> >>
> >> Hard to believe in german, but obviously true.
> >>
> >>
> >>
> >> My QTH is Siegburg JO30OT
> >>
> >>
> >>
> >> Horst
> >>
> >>
> ___________________________________________________________
> >>
> >> NEU: Mit WEB.DE DSL über 1000,- ¿ sparen!
> >>
> >> http://produkte.web.de/go/02/
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> --
> >>
> >>
> >>
> >> http://g3xbm-qrp.blogspot.com/
> >>
> >> http://www.g3xbm.co.uk
> >>
> >> http://www.youtube.com/user/G3XBM
> >>
> >> G3XBM GQRP 1678
> ISWL
> >> G11088
> >>
> >>
> >>
> >>
> >>
> >>
> >> --
> >> ----------------------------
> >> Dipl.-Ing. Stefan Schäfer
> >> Institut für Umweltphysik der Universität
> >> Heidelberg
> >> Im Neuenheimer Feld 229
> >> D-69120 Heidelberg, Germany
> >>
> >> [email protected]
> >> Phone: (+49) (0)6221 546387
> >> Fax: (+49) (0)6221 546405
> >>
> >>
> www.iup.uni-heidelberg.de
> >>
> >>
> >>
> >
> >
>
>
>
>
>
>
>
>
>
|
