Re: LF: Re: RE: Folded monopole - Food for thought

[Andy Talbot <andy.g4jnt@gmail.com>]

Yes, but we're nearly always talking small antennas here,  where Rrad is more like a few milli-ohms and the overall extra loss  resistance totally dominates

Andy

On 15 August 2015 at 18:28, Clemens Paul <cpaul@gmx.net> wrote:

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: owner-rsgb_lf_group@blacksheep.org
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Andy Talbot
>Sent: Friday, August 14, 2015 10:38 PM
>To: rsgb_lf_group@blacksheep.org
>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
><alan.melia@btinternet.com> 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
>
>