[TowerTalk] Take off angles, VOACAP, etcf.

[Pete Smith]

This is a very good point.  Initially, N6BV did his histograms of arrival 
angle distribution using real antennas at both ends of the path.  Now he 
uses isotropic sources with gain, if I recall correctly.  I have to take 
some of the blame for convincing him to make the change.

I think you need both, really.  It strikes me that when you're trying to 
scrape up yet another layer of weak Europeans, you can assume that very low 
angles are irrelevant, because you've worked your way down to the 5 
watt/indoor dipole guys.  Any signal they are getting to the ionosphere is 
unlikely to be at less than 5 degrees takeoff angle.

73, Pete N4ZR

At 02:26 AM 10/17/2004, Guy Olinger, K2AV wrote:

>That's the d*mned if you do, d*mned if you don't issue IF you only publish 
>one kind of measurements.
>
>If you don't do isotropic figures, then you can't adjust for your own 
>antennas. But you ALSO need to do some runs accounting for a far end that 
>has a dipole at 40 feet and couldn't transmit a signal below 15 degrees if 
>his life depended on it, no matter what VOACAP picks as the best angle for 
>broadcasters.
>
>That's when you start to understand how higher angles are going to help 
>you work the next layer of signals in a contest.
>
>Anybody can work the guy on the other end running a KW and a beam up 30 
>meters. It's his buddy down the block running 10 watts and an antenna 
>draped over a couple of short trees that will test one's rig and choice of 
>antennas.
>
>Guy.
>
>
>----- Original Message ----- From: "Jim Lux" <jimlux at earthlink.net>
>To: "Jim Lux" <jimlux at earthlink.net>; "Guy Olinger, K2AV" 
><olinger at bellsouth.net>; "W3YY" <w3yy at cox.net>; "TowerTalk List" 
><towertalk at contesting.com>
>Sent: Saturday, October 16, 2004 11:48 PM
>Subject: [TowerTalk] Take off angles, VOACAP, etcf.
>
>
>>I've been giving some thought to the VOACAP amateur radio thing..
>>
>>If you run VOACAP, it displays the dominant path (and it's takeoff angle,
>>which is presumably what N6BV used in building the statistical tables).
>>However, I wonder what antenna was used. If it was an isotrope, all paths
>>would be weighted evenly in the selection, which will tend to favor the low
>>angle one hop path, as opposed to the high angle two hop path.
>>
>>If you give VOACAP a realistic pattern typical of most ham antennas, which
>>have terrible gain below a few or 10 degrees, that might favor the high
>>angle two hop path, which would account for Guy's comments.
>>
>>Hmm..
>>
>>
>>
>>_______________________________________________
>>
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>>any questions and ask for Sherman, W2FLA.
>>
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>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>any questions and ask for Sherman, W2FLA.
>
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