That's right Tom.
Since, from the original question, I deduced that the questioner was not
that sophisticated, I referred him to the Force12 antenna spec URL which
goes into much detail on this.
Those of us who have modeled antennas for years and studied this subject
will not be confused.
You are correct in your comment, but it's all in the Force12 URL, so I gave
him the endpoints and referenced it.
Bill, N3RR
-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of n4kg@juno.com
Sent: Friday, July 13, 2001 6:09 PM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] Tennadyne T7 DB Gain Question
Bill,
I feel that your third paragraph is misleading and needs
further clarification. Specifically, dBi = dBd + 2.18 dB in
FREE SPACE.
Over ground, ANY horizontally polarized antenna will pick
up 5 to 6 dB GROUND REFLECTION GAIN (6 dB over
"perfect ground") which has absolutely NOTHING to do
with the gain characteristics of the antenna.
This ground reflection gain is at the peak of the first lobe.
The peak angle depends of course on height above ground
in wavelengths.
Tom N4KG
On Fri, 13 Jul 2001 "Bill Hider" <n3rr@erols.com> writes:
>
> Joe,
>
> dBd is "gain over a dipole".
>
> "Real gain", as you call it, has no meaning. Each person defines
> "real gain" in their own terms.
>
> For horizontal antennas, you would ADD approximately 7 - 7.5 dB to
> the dBd figure to get dBi, the gain over an isotropic source at the
same
> height.
>
> There is an excellent discussion on this subject in the Force12
> catalog> which is downloadable from their website:
http://www.force12inc.com/
>
> see: http://force12inc.com/F12-ant-specs-r31.htm
>
> Bill, N3RR
>
> -----Original Message-----
> From: owner-towertalk@contesting.com
> [mailto:owner-towertalk@contesting.com]On Behalf Of k0bx@qsl.net
> Sent: Friday, July 13, 2001 3:02 PM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Tennadyne T7 DB Gain Question
>
> I am looking to replace my Hygain DB10/15 Dualband beam with a
> Tennadyne T7 18-33 MHZ log. It would be located under my Hygain
> 204BA (20 Meter Monobander).
> On the Tennadyne website it give the gain figure as
> "6.2 dBd"? I am not sure what dBd is? Should I subtract 3 from
> the figure to get the real DB gain?
> Anyone have this antenna and have a comment about it?
> Thanks
> Joe K0BX
>
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