Re: [TowerTalk] Re: One more ground radial question

[Jim Lux <jimlux@earthlink.net>]

At 05:09 PM 12/18/2003 +0100, Jan Erik Holm wrote:
> You need no helicopter. In practical sense just
> measure the ground wave.
> We are not trying to confirm loobes in the vertcal
> plane, then you need helicopters.
>
> 73 Jim SM2EKM


But, for HF skywave communications, you ARE very concerned about the 
skywave.  The near and midfield (say, out to 10-20 wavelengths) will have a 
huge effect on what the pattern looks like close to the ground, or, at 
least up to 20-30 degrees, which is usually what folks are worried about.

It would be very, very difficult to relate, with any confidence, the 
measurements you might make at ground level to the gain at 5,10, or 20 
degrees above the horizon. (unless you're like Rick Karlquist, with an 
antenna out Galt,CA in the middle of a flatter than Kansas plain with 
fairly uniform soil characteristics for miles in every direction)

A very small change in the soil characteristics radically changes the depth 
of the "null" at the horizon for horizontally polarized antennas over 
ground. Less of an effect for the vertically polarized antennas. Since 
almost all practical antenna systems radiate both polarizations, and the 
skywave itself is fairly randomly polarized, such things are important.







> ---------------------
>
> Jim Lux wrote:
>
> > Hard to do, in a practical sense... You'd need a measurement receiver in an
> > airplane, helicopter, balloon etc, because the field strength at "ground
> > level" isn't really what you're interested.
> > Perhaps measuring beacons before and after?  But you've got the propagation
> > variations to worry about.
> > This is why evaluating HF antennas is such a royal pain.
> > ----- Original Message -----
> > From: "Jan Erik Holm" <sm2ekm@telia.com>
> > To: <towertalk@contesting.com>
> > Sent: Wednesday, December 17, 2003 8:37 PM
> > Subject: [TowerTalk] Re: One more ground radial question
> >
> >
> > > Is something like this ever confirmed by field
> > > strenght measurements?
> > >
> > > 73 Jim SM2EKM
> > > --------------------------------------------------
> > >
> > > Don Havlicek wrote:
> > >
> > > > Yes!
> > > > In my case ... 60 radials spaced 6 degrees apart .. then concentrations
> > > > of ten radials at 1 degree each for Europe, Japan, South America, and
> > > > VK/ZL ... works like gangbusters .. all I need now is to clean out the
> > > > shack and put a new feedline out to the vertical again!
> > > > Don
> > > > N8DE
> > > >
> > > > va3pl@cuic.ca wrote:
> > > >
> > > >
> > > > > ----- Original Message ----- From: "Don Havlicek" <n8de@thepoint.net>
> > > > > To: <kb9cry@comcast.net>
> > > > > Cc: <TowerTalk@contesting.com>
> > > > > Sent: Wednesday, December 17, 2003 12:12 PM
> > > > > Subject: Re: [TowerTalk] One more ground radial question
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > I believe the word "optimum" should be replaced with "sufficient".
> > > > > > My experience with verticals tells me that 100 radials works much
> > > > > > better than 60, especially when concentrated in certain directions.
> > > ,
> > >
> > >
> > > _______________________________________________
> > >
> > > 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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> > > TowerTalk@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> _______________________________________________
>
> 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.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk

_______________________________________________

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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