Hi Stefan, I am not sure about your aluminium foil idea. I worry that this will
form a lossy capacitor because the dielectric a think film of ali oxide will
break down in places at this voltage and also there is the inknown of the
contact with the ground. I would rather use some UR67 it can be a length
unsuitable for real feeder work (I uses coax as a capacitor in an HV pulse
generator many years ago and though the spec is 6kV it certainly survived 15kV
with no burns though the dielectric. Rik and I discussed this format at length
many years ago for 136kHz but I dont think either of us did any tests.
I would suggest an HV capacitor might be the alternative old TV EHT type??
Actually grounding the remote ends is a lot easier and a lot less to carry if
you are operating "portable"
Alan G3NYK
--- On Mon, 22/2/10, Stefan Schäfer <[email protected]> wrote:
> From: Stefan Schäfer <[email protected]>
> Subject: AW: LF: VLF_8.79 kHz
> To: [email protected]
> Date: Monday, 22 February, 2010, 23:36
> Rik, Alan,
>
> I think we think about the same: using the inv-L as a
> vertical loop by using the ground.
>
> Wouldn't it be easier to use a aluminium foil to get proper
> C (to ground), especially when talking about high voltages
> and high currents? Just covered with some soil and easy to
> adjust/modify...
>
> Stefan
>
> ________________________________
>
> Von: [email protected]
> im Auftrag von Rik Strobbe
> Gesendet: Di 23.02.2010 00:12
> An: [email protected]
> Betreff: RE: LF: VLF_8.79 kHz
>
>
> Pete,
>
> what about putting a large (1..10nF) cap from the antenna
> base to ground ?
> It would reduce the required inductance with a factor 10 to
> 100 and at the same time transform the high loss resistance
> (I gues 1kOhm or more) to a more convenient value.
> Of course the cap needs to handle the high antenna voltage,
> so power should be more modest than 780 Watt.
> A ready available source of HV caps is RG8 / RG213 or
> similiar coax cable that can handle many kV's. At 101pF/m
> you would 10 to 100m cable.
>
> 73, Rik
>
> ________________________________
>
> Van: [email protected]
> [[email protected]]
> namens M0FMT [[email protected]]
> Verzonden: maandag 22 februari 2010 23:43
> Aan: [email protected]
> Onderwerp: RE: LF: VLF_8.79 kHz
>
>
> 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]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
>
> [mailto:[email protected]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
> ] On Behalf Of Warren Ziegler
> Sent: 22 February 2010 16:23
> To: [email protected]
> <http://uk.mc281.mail.yahoo.com/mc/[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]
> <http://uk.mc281.mail.yahoo.com/mc/[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]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
> > wrote:
> >
> >> From: Stefan_Schäfer <[email protected]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
> >
> >> Subject: LF: VLF_8.79 kHz
> >> To: [email protected]
> <http://uk.mc281.mail.yahoo.com/mc/[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 ; <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]
> <http://uk.mc281.mail.yahoo.com/mc/[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]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
>
> >> im Auftrag von Horst Stöcker
> >>
> >>
> >> Gesendet: Mo 22.02.2010 09:29
> >>
> >> An: [email protected]
> <http://uk.mc281.mail.yahoo.com/mc/[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.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]
> <http://uk.mc281.mail.yahoo.com/mc/[email protected]>
>
> >> Phone: (+49) (0)6221 546387
> >> Fax: (+49) (0)6221 546405
> >>
> >> www.iup.uni-heidelberg.de
> >>
> >>
> >>
> >
> >
>
>
>
>
>
>
>
|
