From: "Mike Dennison" <mike.dennison@ntlworld.com>
To: rsgb_lf_group@blacksheep.org
Date: Sat, 07 Nov 2015 10:58:02 -0000
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References: <1843908200.20151104162925@chriswilson.tv>, <CAA8k23QB1RxnKaYXrYq0YVscvzEsNstciTwTkW=D6Dvt2fLUYQ@mail.gmail.com>, <8E31BC8EB75546E59F99E35AFAAA0DEE@AGB>
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Subject: Re: LF: Capacitive top hat question
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Status: O

To all intents and purposes a short (in wavelengths) vertical 
attached to an arrangement of horizontal wires is a simple 
(capacitively) loaded vertical. 

The horizontal part will radiate, especially if it has a vertical 
component rising higher than the feedpoint, but most of that 
radiation will be cancelled by its reflection in the ground.

Several unbelievers have tried using purely horizontal transmitting 
antennas and have had poor results. The beauty of amateur radio is 
that you can prove something to yourself, but it won't change the 
laws of physics.

Of course, every electrically small Marconi that is not in free space 
performs in a complex way, but the result of that complexity is small 
compared to the predominent omnidirectional radiation from the 
vertical section. There is very little difference between various 
arrangements of capacity hat, so long as you follow the rule to put 
up as much wire as possible, as high as possible and covering as much 
ground as possible.

Mike, G3XDV
==========

> Not sure why you talk about wire separation,
> 
> Verticals  properly  are  quire simple, this is not a  pure vertical 
> and not  very  simple  to  evaluate ,  Your making the  assumption,
> that the  system stops radiating  at the  point  of  connection  to
> the  loop ? .
> 
> The  feed  is  at the  corner making a  Y  and  not  a  T .. hence the
>  question  ,  
> 
> At  what  point  dose the  transformation  take  place ,  radiator  to
>  loading  ?
> 
> G,
> 
> 
> From: Andy Talbot 
> Sent: Wednesday, November 04, 2015 9:11 PM
> To: rsgb_lf_group@blacksheep.org 
> Subject: Re: LF: Capacitive top hat question
> 
> 
> 16 US units of length ~ 4.9m, so that means it's a bit more than half
> the height of mine.  The top hat is near-enough infinite to all
> intents and purposes, so its real height is 4.9m.      My antenna is
> only 7m high, with much smaller top hat. That amount of top
> capacitance will drastically reduce the ground resistance, so all more
> than likely all quite an efficient vertical radiator.   If there is
> enough buried metal in the ground it could be very good indeed. so
> we're probably talking about a similar performance - perhaps an
> efficiency of -40dB on 137kHz.  That's what mines comes out as,
> anyway.
> 
> 
> 
> Horizontal radiaitors don't when they are close to a reflector.   And
> the same good ground system that makes it radiate vertically stops the
> horizontal bit doing anything.   If the ground were very poor, sand
> for instance with littel wire underneath, then perhaps the horizontal
> part may generate some ExH, but then efficiency would no doubt be so
> poor that teh Hpol contribution would be insignificant.
> 
> 
> Not sure why you talk about wire separation, he said they are strapped
> so its just a two wire, fat vertical.  Which is exactly what I use -
> two paralleled conductors of a twin feed.
> 
> 
> Vertical antennas really are quite straightforward to analyse /
> measure
> 
> 
> Andy  G4JNT
> 
> 
> 
> 
> 
> 
> On 4 November 2015 at 20:21, Graham <g8fzk@g8fzk.fsnet.co.uk> wrote:
> 
>   I dont think its  that  simple Andy ,
> 
>   16 ft is  not  much  for  136 ,  and the  loop  runs  up from  the 
>   feed  point , which I think  is  a  corner ,, so  at  what  point 
>   is  it a radiating  element  and  which  point  is it   top  loading
>    
> 
>   Ae could look like a sloping  Y  at  some  point , the  wire 
>   separation  must be  too  much to  act  as  one  ?
> 
>   G,
> 
> 
> 
> 
>   From: Andy Talbot 
>   Sent: Wednesday, November 04, 2015 8:00 PM
>   To: rsgb_lf_group@blacksheep.org 
>   Subject: Re: LF: Capacitive top hat question
> 
> 
>   A pretty thoroughly top loaded vertical, Heff = Hactual 
> 
> 
>   'jnt
> 
> 
> 
> 
>   On 4 November 2015 at 19:50, Graham <g8fzk@g8fzk.fsnet.co.uk> wrote:
> 
>     (about 16 fee thigh, strapped together at the base only)
> 
>     I wonder  what  exactly  is  radiating Chris ?
> 
>     what  to  you  estimate the  beam  pattern to  be ,  I have the 
>     idea , south  to  SV is down , compared to  say  North TF ? , the 
>     levels  into Iceland  are significant ..
> 
>     73-Graham
> 
> 
> 
>     --------------------------------------------------
>     From: "Chris Wilson" <chris@chriswilson.tv>
>     Sent: Wednesday, November 04, 2015 4:29 PM
>     To: <rsgb_lf_group@blacksheep.org>
>     Subject: LF: Capacitive top hat question
> 
> 
>       04 November 2015
> 
> 
>       On my 136khz set up I have a short piece of ladder line (about
>       16 feet high, strapped together at the base only) feeding the
>       corner of my horizontal quad loop, which is about 460 feet in
>       circumference. If I am TX'ing with WSPR I can walk around under
>       all of the loop and a fluorescent tube at waist height will
>       light quite brightly. Should the loop also radiate as well as
>       the vertical section? Sorry for the probably naive question, I
>       am not sure whether it's normal or not, thanks.
> 
> 
> 
>       -- 
> 
> 
>       Best regards,
>       Chris                            mailto:chris@chriswilson.tv
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
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