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From: =?ISO-8859-15?Q?Horst_St=F6cker?= <horst.stoecker@web.de>
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Subject: Re: AW: LF: AW: 8.97kHz - Near field and radiated signals?
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Hello Stefan,
yes, you understood right: I am preparing for a test with a big earth base=
 of some 100m. I will announce it here.
For my first tests with an audible signal in about 100m distance I used no=
 TV transformer but an audio transformer.
Now with the TV transformer the signal is much louder.
Once again: Mode: CW, TX 300W > TV transformer > 10h/20t T-antenna; RX AAT=
IS VLF-RX with whip antenna.
The mean problem and also the reason why I am at the really beginning of=
 my experiments is that now everything has to be tested under better condi=
tions than inbetween houses and trees - and also with QRSS and Laptop. I=
 hope I can tell yomething more this week.
vy73 Horst DO1KHS/DI2AN


-----Urspr=C3=BCngliche Nachricht-----
Von: "Stefan Sch=C3=A4fer" <schaefer@hst.tu-darmstadt.de>
Gesendet: 24.05.2010 23:27:34
An: rsgb_lf_group@blacksheep.org
Betreff: AW: LF: AW: 8.97kHz - Near field and radiated signals?

>Hi Horst,
>=20
>I remember the times in Februar (or was it Januar?) where you gave us tha=
t little information about your test on VLF that caused all the following=
 things ;-) Nice to read the mails that came after taht time and what happ=
end in the following weeks :-)))=20
>So, you also have used a TV transformer on your vertical antenna? Pse, wh=
at was the voltage you achieved? And what was the distance? What was your=
 RX mode? (QRSS...?).
>=20
>Have i understood that right, you want to try a 800m (or 2x 800m?) ground=
 electrode antenna? That would be very nice! :-)
>=20
>73 es gl
>=20
>Stefan
>
>________________________________
>
>Von: owner-rsgb_lf_group@blacksheep.org im Auftrag von Horst St=C3=B6cker
>Gesendet: Mo 24.05.2010 19:18
>An: rsgb_lf_group@blacksheep.org
>Betreff: Re: LF: AW: 8.97kHz - Near field and radiated signals?
>
>
>Hello Roger, Dreamers,
>if we define near field as < 2 lambda we are talking about everything bel=
ow 60 km.With this distance I woul be extremely lucky.
>I also do "walkaround tests" near my garden. But I bet only in the flat=
 field one can see what is possible with small antenna an without a big lo=
ading coil.
>Out from my garden I tried my 10h/20t Marconi as well as a 30m earth base=
. The Marconi worked better, but not good enough. A TV transformer (must=
 be flyback of course) made it much better.
>But all the trees and houses are coupling the radiated signal to earth an=
d also the AATIS-RX is very much influenced by them.
>I also assume that the horinontal parts of a wire do the same. So only a=
 vertical should work.
>For operation in city environment smaller antennas at the roof top (old=
 CB antennas) will possibly work better than the bigger vertical in my gar=
den between trees and houses at ground level. It might be worth a test.
>One of the next tests will be with my gig earth base. I have collected ab=
out 800m of surplus wire. Possibly this is another way to even radiate mor=
e then near field. But I would be very surprised it this was good for any=
 DX.
>I bet Stefans kite antenna will at least be the only way to DX operation.=
 Unfortunately this is just portable and just temporary.
>vy73 Horst DO1KHS/DI2AN
>
>
>
>________________________________
>
>   Von: Roger Lapthorn <rogerlapthorn@gmail.com>
>   Gesendet: 24.05.2010 18:36:28
>   An: rsgb_lf_group@blacksheep.org
>   Betreff: Re: LF: AW: 8.97kHz - Near field and radiated signals?
>  =20
>   Thank you for your fast reply Stefan.
>  =20
>   In answer to your questions:
>  =20
>
>   *   Currently, my TX electrode spacing is 10m, which is the best I can=
 manage in my small garden. Both electrodes are as far away from the mains=
 and other utility services as I can manage.=20
>   *   I have not tried /P transmit testing yet.=20
>   *   My nearest ham who will listen/look is 3kms away, but using beacon=
ing I am able to go out myself and see how far I can reach. This is what=
 I have done so far, going out into the fields behind my house with electr=
ode pairs or a loop receiver. Best (by ear reception) DX is 0.35kms, but=
 the system has much scope for optimisation still.=20
>   *   The largest single turn loop I could erect in my garden would be=
 about 50-70 sq m (about 15m top and 4m-5m high). The longest antenna leng=
th would also be 15m horizontal with some vertical section(s) too.=20
>   *   The best DX targets are quite modest: I would like to exceed 1km=
 initially with the TX power I currently have (around 4W). If I could reac=
h G6ALB in the next village 3kms away I would be delighted. If I got any=
 further I would be both amazed and VERY happy!=20
>
>   73s
>   Roger G3XBM
>  =20
>  =20
>  =20
>   2010/5/24 Stefan Sch=C3=A4fer=20
>  =20
>
>       Hello Roger,
>      =20
>       For your ground electrodes, ground electrodes may be the best "ant=
enna" in some 10...10m. I'm not sure how to calculate field strengths but=
 i just know about the 1/d^3 dependency, so twice the distance means 8 tim=
es the power for the same signal reception, in the near field. But it is=
 the question what are the electrodes since there is ever a coupling to th=
e mains earth and all the metallic stuff in regions where people are livin=
g so this dependency might not be valid in your tests. As mentioned here,=
 you could benefit from these conductors...
>      =20
>       But if you want to reach more distance with an antenna of the same=
 size (e.g. of your garden)and the same power, you could try such a TV tra=
nsformer. Take a wire, as long as possible and as high as possible, and ap=
ply some kV on it by this transformer. It can even be resonated by adjusti=
ng the air gap between the both ferrite parts. That results in a maximum=
 output voltage and thus "ERP". At least this would be a good alternative=
 to your ground electrode tests. You could easily compare the reachable di=
stances. Here i would use a E field antenna for reception in the near fiel=
d.
>      =20
>       How far is your next receiving amateur radio station away? And hav=
e you tried to do such tests outside the village/city, just like Jim does=
 it with his loop antenna? This could allow you to increase the distance=
 of your reception. Here, space is not limited and you could try 2x10m, 2x=
50m, 2x100m and so on and tell us the difference in the feed point impedan=
ce at various frequencies and your ODX :-) Maybe i will also do some groun=
d electrode tests in summer but i am still not sure. The complete receiver=
 of Jim is a really good idea to check the QRM situation at a given QTH.=
 Probably i will also buit his loop design for such tests... Would be inte=
resing what is the maximum distance for a CW reception of my transmitted=
 signal (with the kite antenna and 6mW ERP) ;-)
>      =20
>       I will also do some near field tests in this week, to compare the=
 performance of my 2 grabbers. This will be done here: http://www.google.d=
e/maps?f=3Dq&source=3Ds_q&hl=3Dde&geocode=3D&q=3Dheiligenberg+heidelberg&s=
ll=3D47.820666,9.312449&sspn=3D0.106733,0.219383&g=3Dheiligenberg&ie=3DUTF=
8&hq=3D&hnear=3DHeiligenberg&ll=3D49.419391,8.704101&spn=3D0.001616,0.0034=
28&t=3Dh&z=3D18 in about 1,8km distance to my grabbers. Power will also be=
 below 100W and the antenna wire will be mounted on a tower in abt 15m hei=
ght. I will transmit with this TV transformer on a 40m wire.
>      =20
>       Roger, what size is your garden? What is the maximum wire length=
 that you can apply and in which height? What is your goal (best DX, a rea=
ls QSO with the next equipped station or just do some funny tests?)
>      =20
>       So, wish you fun and success with your experiments!
>      =20
>       73, Stefan/DK7FC
>      =20
>       PS: What is your locator / QTH?
>      =20
>      =20
>
>
>
>
>   --=20
>   http://g3xbm-qrp.blogspot.com/
>   http://www.g3xbm.co.uk <http://www.g3xbm.co.uk/>=20
>   http://www.youtube.com/user/g3xbm
>   G3XBM    GQRP 1678      ISWL G11088
>  =20
>
> =20
>
>
>  =20
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