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Re: [TowerTalk] HFTA and diferent bands antennas

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] HFTA and diferent bands antennas
From: jimlux <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Sat, 24 Apr 2010 17:52:53 -0700
List-post: <">>
David Gilbert wrote:
> The REAL Swiss Army knife for antenna modeling would, in my opinion, 
> combine the terrain analysis of HFTA with the antenna modeling 
> capability of NEC .... and do it for both transmit and receive.  I 
> remain convinced that, especially for low angle signals, asymmetric 
> terrain that "looks different" to an outgoing signal than it does to an 
> incoming signal can cause dramatically different signal levels on the 
> two ends of a QSO even if all other considerations (power level, 
> antennas, noise level, ground conditions, etc) are equal. 

I don't know about that... That would imply a violation of reciprocity, 
wouldn't it?

I would believe non-symmetric propagation via skywave, but not that the 
"effective antenna pattern" is different for transmit/receive.

  N6BV even
> alludes to that possibility in the ARRL Antenna Book discussion of 
> HFTA.  I've privately encouraged him ... begged is probably a more 
> accurate description  ... to write an arrival angle version of HFTA, and 
> he indicated that if he ever decided to tackle such a task it would be 
> sometime in the future.  I fully understand that.  It would be a totally 
> different and probably much more complex problem since the incoming 
> signal wouldn't be a point source like the outgoing signal is.  Still, 
> I'm desperately hoping he gives it a try some time.
> And of course there's always vertical polarization .... ;)

which makes the reflection calculations MUCH more complex (for 
horizontal, it's much easier)

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