HI Clemens,
but on LF Rrad <<< Rloss, in that case it is very close to 6dB.
And often adding a topload wire will decrease Rloss (footprint theory), so the
actue gain will often be more than 6dB.
73, Rik ON7YD - OR7T
________________________________________
Van: [email protected] [[email protected]]
namens Clemens Paul [[email protected]]
Verzonden: zaterdag 15 augustus 2015 19:28
Aan: [email protected]
Onderwerp: RE: LF: Re: RE: Folded monopole - Food for thought
Hi Andy,
>6dB more, not 3dB
>Height squared
I believe it's neither 3dB nor 6dB increase for ERP.
What is squared by doubling the effective height is is Rrad.
The increase in ERP is by far not so high and depends much on Rloss (ground and
matching).
Example:
Rrad = 50 Ohm; Rloss = 50 Ohm => efficiency = 0.5
Quadruple Rrad to 200 Ohm then efficiency = 0.8 => 2dB more.
Other Rloss values give completeley different numbers for efficiency.
73
Clemens
DL4RAJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Andy Talbot
>Sent: Friday, August 14, 2015 10:38 PM
>To: [email protected]
>Subject: Re: LF: Re: RE: Folded monopole - Food for thought
>
>6dB more, not 3dB
>Height squared
>
>'jnt
>
>
>On 14 August 2015 at 22:31, Alan Melia
><[email protected]> wrote:
>
>
> The problem with a monopole at LF is that the effective
>height is only half (approx) the physical height. For an
>inverted L where the top length is at least twice the height,
>the effective height is close to the physical height .....so
>3dB more ERP. It may not matter so much on 160m (I used a
>16foot centre loaded "tank-whip" at one time :-)) ) but where
>
>
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