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@k9ay.com>
To: "Guy Olinger, K2AV" <olinger@bellsouth.net>;
<antennaware@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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