Message-ID: <C7FB46180B944782899817F9A6D0D228@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <Pine.LNX.3.95.1100301013359.218A-100000@noname.nodomain.nowhere> <34EE45A0413B499D9FD2861D88BD4AE1@AGB> <4B8CE53D.4050300@ukonline.co.uk>
In-Reply-To: <4B8CE53D.4050300@ukonline.co.uk>
Date: Tue, 2 Mar 2010 17:25:55 -0000
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Subject: Re: LF: 9kHz without high voltage
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Peter

Yes , the  counter wound construction was challenged during the  lecture and 
the  concept  of a  mirror was introduced  ... this then  negated any 
constructional / geometric problems , by simply using the  induced eddy 
currents in the  metal plate to  produce a  virtual 'mirror' image of the 
coil ... an exact copy ... Thus the  feed requirements where  reduced to 
one end of the  coil and the  back plate ...

I made  one based on the concept  outlined during the  lecture , 12 inch 
diameter coil ,  3 inch x 3/16  pitch , resting on a 1/8 perspex plate on a 
3  ft  diam alloy  plate resting on a plastic dust bin . , fed with a  short 
length  of 450  ribbon cable  via a  air spaced balum from a racal auto 
tuner , the  results where  quite  odd , it  basically  worked on all  bands 
from 160  to  10 , the  tuner achieved a  good match.

Running  150  watts  , it  gave  good  reports  round Eu on 80 , 14  was 
very lively  and a  Russian found it  quite  funny  that  he was getting a 
10  over 9  signal on 10 mt from a  garden bin .. even at  400 > 450  watts 
carrier power the  ae did  not  flash over  or heat up ..how it  worked ive 
no idea !  but the  mirror concept seemed to be the  missing like that  no 
one had though of .. im sure  some one at the  lecture made a video of it 
....

A very small  2 mtr one was also  demonstrated , using  9  turns  app  10 
mm dial round a  10 mm former and a  100 / 75  mm disc , apparently  he had 
used it mobile with  good  results.  I have the  idea  a  6  ft  back plate 
with a  3  ft  x  6 inch coil may work on 500  .. ive yet to  find the  6 ft 
plate ....

Very sad to  see  he has passed on , as its possible a lot of his later work 
may  of been  lost ?

G ..

--------------------------------------------------
From: "Peter Dodd" <g3ldo@ukonline.co.uk>
Sent: Tuesday, March 02, 2010 10:15 AM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: 9kHz without high voltage

>
> When I was technical editor at the RSGB in 1994 an interesting article was 
> received from Prof Jennison G2AJV on a toroidal antenna. Before publishing 
> it I felt that I should make one. This turned out to be a problem but 
> after several phone calls with G2AJV a 14MHz version using two toroid 
> coils and no end plates was made to work
>  The article was published in RadCom April/May 1994 'The G2AJV Toroidal 
> Antenna'.
>
> After the article was published I continued to experiment with this 
> antenna. I also met Prof James Corum, K1AON at Dayton, who passed on 
> additional information on this antenna - he has a patent on the toroid 
> antenna.
>
> Eventually my 14MHz version performed as well as a 14MHz  loaded whip 
> antenna and the whole saga was written up in RadCom August 1994 
> 'Evaluation of the G2AJV toroid antenna'.
>
> All these RadCom articles are well illustrated with colour photos.
>
> Regards
>
> Peter, G3LDO
>
>
>
>
> On 01/03/2010 19:56, Graham wrote:
>> Making  a   Torodial  antenna, as  presented at the  Egham HFC  would be 
>> a good  start .. the  concept  of the  mirror differed  from the 
>> published articles ... I made one and oddly it  worked  quite  well  at 
>> Hf  ..how it worked ive no idea .how a  12 inch diameter  coil resting on 
>> a old  no-entry sign (alloy plate) one end fed with coax from the  atu 
>> the  other  open achived qso's  from 160  to  10 mtrs .. who  knows .... 
>> .its  still hanging in the  shed .. but a  large one may work at  9 khz 
>> without the  need  for all  the  coils  etc ...  Did  anyone else  attend 
>> the  lecture ?.. it followed the  chap from Birmingham with a selection 
>> of  loop  antennas . ....
>>
>> G ...
>>
>> NB .. Can anyone  read this  .. as  '' design of toroidal reflector ..... 
>> Antennas ''  is  showing in the  google  search
>>
>> http://www.informaworld.com/smpp/content~content=a770413350&db=all
>>
>> --------------------------------------------------
>> From: "Alexander S. Yurkov" <fitec@omskcity.com>
>> Sent: Monday, March 01, 2010 1:59 AM
>> To: <rsgb_lf_group@blacksheep.org>
>> Subject: LF: 9kHz without high voltage
>>
>>>
>>>
>>> I was wonder if it is posible to use a loop on 9 kHz. Serious problem
>>> to radiate 9 kHz is high voltage we saw. Loop has that advantage that
>>> voltage is not too high. Then i do some estimations. Let's assume 
>>> vertical
>>> loop 15m x 50 m with 20 mm diameter coper tube as a wire. Then 
>>> effectivity
>>> of such a loop on 9 kHz is about -65 dB. It is adequate to radiate 1 mW
>>> on 9kHz (I=250A, TX power about 4 kW). We saw such a radiation should
>>> give abt 100 km  distance in QRSS. Besides such a loop is wellsuited
>>> for 136 kHz. On 136 kHz it effectivity should be about -25 dB. Not too
>>> bad: 1 W radiation with 400 W TX :-)
>>>
>>> Regards,
>>> Alexander
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>
>
>