Topband: Modeling the proverbial "vertical on a beach"

[Hardy Landskov]

Just an observation to all:
When Tom, N6BT went to Jaimaca and operated 6Y2J (I think was the call) with 
verticals on the beach I was blown away. I heard them 2 hours before Sunset 
here on 160....nuff said. The proof is in the pudding.
73 N7RT

----- Original Message ----- 
From: "Guy Olinger K2AV" <k2av.guy at gmail.com>
To: "Richard Fry" <rfry at adams.net>
Cc: "TopBand List" <topband at contesting.com>
Sent: Saturday, August 09, 2014 8:35 PM
Subject: Re: Topband: Modeling the proverbial "vertical on a beach"


> Just to mention that the prior opinion is controversial and not 
> universally
> agreed upon. Nor to date has anyone surfaced with actual measurements made
> at the distances (25 to 50 km) and with span of altitudes (0 to 10 km) to
> either prove or disprove either side.
>
> It remains unproven modelling from NEC at those distances either way. This
> situation may, alas, persist this way, because the precise subject
> resolution appears to be without benefit to any commercial interest and
> therefore without funds to pay for some pretty expensive experimenting
> involving precision measurements from aircraft.
>
> Additionally, there is considerable suspicion that moving from LF to MF in
> this general subject involves a ground modal change of some sort that 
> would
> render 50x10 km measurments at 0.5 or 1 MHz unlike those at 2 MHz,
> rendering commercial measurements at low and possibly high BC of no value
> for extrapolation to ham use.
>
> Arguments on both sides remain basically intuitive. I have "reasonable"
> arguments to BOTH concur with Richard AND to not. NEC near field
> calculations over sea water at 50 km follow Richard's assertions, and the
> same over "average" ground does not. The model clearly thinks that 50 km
> over most types of ground slowly dissipates low angles resulting in the
> controversial "notch" in low angle elevation patterns.
>
> So NEC based modelling cannot be used as a proof text to decide an 
> argument
> NEC has with itself.
>
> 73, Guy K2AV.
>
>
> On Sat, Aug 9, 2014 at 7:23 PM, Richard Fry <rfry at adams.net> wrote:
>
>> Just to note that the low-angle radiation produced by monopoles is not
>> accurately shown by a NEC model/study that does not include the surface
>> wave, regardless of whether one or two ground-plane media are specified 
>> in
>> the model.
>>
>> Below is a link to a NEC study of the low-angle fields of a monopole
>> __including the surface wave__ for three values of earth conductivity
>> ranging from extremely good to very poor.
>>
>> The curves there all show maximum relative field in the horizontal plane.
>>
>> If the surface wave had not been included in these studies then all of
>> those fields would have a zero value in the horizontal plane, and reduced
>> fields at low angles just above the horizontal plane.
>>
>> Reality is that radiation leaving the monopole at elevation angles of at
>> least 5 degrees decays at a 1/r rate.  Therefore that radiation is a 
>> space
>> wave which propagates in a ~ straight line to reach the ionosphere, where
>> (with suitable conditions) it can return to the earth as a skywave.
>>
>> NEC analyses of a vertical monopole of 5/8-lambda and less, and not
>> including the fields of the NEC surface wave do not recognize the 
>> radiation
>> sector capable of producing the greatest single-hop skywave service range
>> that can be provided by that monopole.
>>
>> http://s20.postimg.org/9xqgzu9d9/Monopole_Low_Angle_Radiation.jpg
>>
>> R. Fry
>> _________________
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>>
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