Re: LF: VLF_8.79 kHz

[riese-k3djc@juno.com]

werent there some tests using the sewer pipes as antennas ?

the cast iron increase in IR losses would be off set by the diameter

of the Pipe  ?? I kinda remember something about that some years ago

 

Bob K3DJC

 

On Tue, 23 Feb 2010 00:12:03 +0100 Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> writes:

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: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens M0FMT [m0fmt@yahoo.co.uk]
Verzonden: maandag 22 februari 2010 23:43
Aan: rsgb_lf_group@blacksheep.org
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 <Rik.Strobbe@fys.kuleuven.be> wrote:

From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
Subject: RE: LF: VLF_8.79 kHz
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
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: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens M0FMT [m0fmt@yahoo.co.uk]
Verzonden: maandag 22 februari 2010 19:19
Aan: rsgb_lf_group@blacksheep.org
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 <james.cowburn@virgin.net> wrote:

From: James Cowburn <james.cowburn@virgin.net>
Subject: RE: LF: VLF_8.79 kHz
To: rsgb_lf_group@blacksheep.org
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: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Warren Ziegler
Sent: 22 February 2010 16:23
To: rsgb_lf_group@blacksheep.org
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 <alan.melia@btinternet.com>
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
<Stefan.Schaefer@iup.uni-heidelberg.de> wrote:
>
>> From: Stefan_Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>
>> Subject: LF: VLF_8.79 kHz
>> To: rsgb_lf_group@blacksheep.org
>> 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
>> <schaefer@hst.tu-darmstadt.de>
>>
>>   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: owner-rsgb_lf_group@blacksheep.org
>> im Auftrag von Horst Stöcker
>>
>>
>> Gesendet: Mo 22.02.2010 09:29
>>
>>     An: rsgb_lf_group@blacksheep.org
>>
>>
>> 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
>>
>> schaefer@iup.uni-heidelberg.de
>> Phone: (+49) (0)6221 546387
>> Fax: (+49) (0)6221 546405
>>
>> www.iup.uni-heidelberg.de
>>
>>
>>
>
>

 

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