[Antennaware] Testing the theory..

Guy Olinger, K2AV olinger at bellsouth.net
Fri Mar 30 21:43:02 EST 2007

Well, good.  Any idea where I might be able to dig up that document? 
Or where to start?

I remember listening to WHO in Columbus, Ohio as an eleven-year old 
with a 5 tube radio after everyone else asleep.  I got ahold of some 
headphones and wired a switch on the dial light so the aydults would 
have no clue.  I sent WHO a postcard and got a QSL card from them. 
That was *before* I ever laid eyes on a ham rig.

Regardless, it begs the question from some posts back, because you can 
bet that WHO had a really "hard" radial system.  The original question 
had to do with *progression* of sky wave strength in synchronization 
with improvement in ground wave as radials were added, going from few 
to many.

I believe that what you quote establishes the validity of the model's 
figures when sufficient radials are in place.  E.g., if you put down a 
commercial quality radial field, it will follow the model.  Certainly 
improves confidence in an assumption of synchronous progress, but 
short of water-tight.  In any event, if one wants the performance, 
then one does the radials

73,  Guy.

----- Original Message ----- 
From: "K9AY" <k9ay at k9ay.com>
To: "Guy Olinger, K2AV" <olinger at bellsouth.net>; 
<antennaware at contesting.com>
Sent: Friday, March 30, 2007 10:41 AM
Subject: Re: [Antennaware] Testing the theory..

> Guy,
> Actually, the regulatory bodies are very interested in skywave
> propagation -- it is the basis for nighttime interference protection 
> among
> AM broadcast stations. But you are correct that skywave is always
> calculated, while groundwave is vertified by field measurement.
> The only well-documented skywave measurement I know of was done many 
> years
> ago at WHO in Des Moines, IA. Their tower is a vertical collinear 
> with a
> phase reversal network at 1/4-wave height. Can't remember where, but 
> I read
> some recent notes that compared Method of Moments modeling with 
> those
> helicopter measurements, and they were remarkably close. Kudos to 
> the old
> timers who made very careful measurements.
> The other part of the story is that the measured data agreed with 
> theory, so
> I am comfortable assuming that skywave radiation is predicted with
> sufficient accuracy by modeling. Groundwave measurements can be used 
> to
> establish overall performance and skywave scaled accordingly.
> 73, Gary
> K9AY
>> What I have never seen documented is actual measurements of 
>> far-field
>> sky-wave changing with numbers of radials, along with the 
>> corresponding
>> measurements at the ground. Sky-wave has always been by inference, 
>> such as
>> how much field is theoretically "available" with a given power 
>> level at
>> the feed, given some "ideal" situation. All had one assumption or 
>> another
>> at root, with one's confidence in the assumption propagated to the
>> inferred sky-wave.
>> It always seemed to me that some very tall non-conducting 
>> structures, or
>> the likes of a helicopter and GPS or some strict, accurate 
>> positioning
>> method for the helicopter would be required to document the 
>> ground/skywave
>> correlation.
>> Since the commercial and regulatory interest at MF was 
>> millivolts/meter at
>> the ground, there doesn't seem to have been much motivation.
>> It's not the sky wave that I would suspect as quirky, but real 
>> ground is
>> subject to such variation as might give some kind of non-linear 
>> result
>> with increasing radials that would not appear in the skywave.
>> 20 degree skywave at a distance of one mile (~10 wavelengths at 
>> 160m)
>> would require an elevation of 1922 feet for the measurement.
>> There may be some directly measured data out there, but I have 
>> never seen
>> it, and would love to see the citation if it exists.
>> 73, Guy.
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