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Re: LF: Re: Inv L 'FAN' top wires ?

To: <[email protected]>
Subject: Re: LF: Re: Inv L 'FAN' top wires ?
From: "Graham" <[email protected]>
Date: Tue, 3 Dec 2013 22:40:33 -0000
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I could  re  make the  2  wire  top  , that  was  3 ft  spacing ,  wind loading  is high  though ..
 
G,

From: Alan Melia
Sent: Tuesday, December 03, 2013 10:14 PM
Subject: Re: LF: Re: Inv L 'FAN' top wires ?

Hi Graham I think that the addition will prove a worthwhile improvement. Try and get the wires over 700mm apart as soon as possible leaving the pole ....use a spreadder ?? stopping the wires at 20ft is fine. I doubt whether there will be a significant deviation from an omni-directional pattern.
 
It would be great if you could measure the capacity  and the resistance (Rrad+Rloss) of the aerial untuned before and after the change.
 
Alan
G3NYK
----- Original Message -----
From: Graham
Sent: Tuesday, December 03, 2013 9:37 PM
Subject: Re: LF: Re: Inv L 'FAN' top wires ?

Err   NCD on that  one  Pete , the  last  'refurbishment'  of the  pole  , attracted  evil spirits ...so at   2x 20  2 inch alloy scaffold poles , that's as  good  as  it  get's  !
 
73-G,

From: M0FMT
Sent: Tuesday, December 03, 2013 9:13 PM
Subject: Re: LF: Re: Inv L 'FAN' top wires ?

 Hi Graham

Probably better to put your efforts into making it higher ?

73 es GL Pete M0FMT IO91UX


On Tuesday, 3 December 2013, 11:25, Alan Melia <[email protected]> wrote:
Hi Graham, this will increase the aerial capacity by around 100 to 120pF provided the new wires are not over/close to lossy foliage/buildings, as the new wires are only the same length as the current wires you will see little increase in Rrad, BUT you will see a proportional decrease in the loss resistance. So the aerial becomes more efficient......this assumes a flat fan not a sloping one. 
 
There is also mileage to be had by connecting the ends of the fan together!! see the measurements Finbar did on the Spiral top loaded systems we tested. http://g3nyk.ham-radio-op.net/spiraltop.htm
 
Approximately, doubling the antenna capacitance halves the  Rloss which is the component determining the antenna current you can drive and hence the ERP.
 
Alan
G3NYK
----- Original Message -----
From: Graham
Sent: Tuesday, December 03, 2013 12:20 AM
Subject: LF: Inv L 'FAN' top wires ?

 
Anyone   tried  this  configuration  ?
 
Changing  single   40 ft  top   wire  on inv-L    to  a   FAN
shape  x3 40 Ft  , spaced  about  10 ft  at  far  end   
 
TNx -G,
 
 
 
 
 
 
 


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