Topband: Modeling the proverbial "vertical on a beach"
Tom W8JI
w8ji at w8ji.com
Sun Aug 10 20:20:49 EDT 2014
How was his signal compared to someone from a similar heading and distance
at the same time who was not on the beach?
----- Original Message -----
From: "Hardy Landskov" <n7rt at cox.net>
To: "Guy Olinger K2AV" <k2av.guy at gmail.com>; "Richard Fry" <rfry at adams.net>
Cc: "TopBand List" <topband at contesting.com>
Sent: Sunday, August 10, 2014 7:35 PM
Subject: Re: Topband: Modeling the proverbial "vertical on a beach"
> 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
>>> _________________
>>> Topband Reflector Archives - http://www.contesting.com/_topband
>>>
>> _________________
>> Topband Reflector Archives - http://www.contesting.com/_topband
>>
>
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>
>
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