[Lowfer] WM too bright!

[John Davis]

>I'm confused. Are you sure that the higher readings at various measuring
>sites in the winter weren't due to improved efficiency of the transmitting
>antenna (a local effect) and had little to do with the soil conductivity in
>the far field?

Over the scale of distance where one proofs a directional array, it could
possibly be either or both.

However, in the kind of studies where one measures soil conductivity over a
specific path to prove that a new assignment will fit, measurements are
taken at many points along a rather long radial, and a curve is fitted to
them that shows attenuation relative to the normalized field at 1 km.
Attenuation beyond the inverse-of-distance falloff is what is needed to
calculate soil conductivity over the given path segments at a given
frequency.

Since the factor being measured there is attenuation, not the absolute field
strength, I believe the anecdotal reports I was referring to in the Plains
were probably indicative of improved conductivity.

John D

-----Original Message-----

>John A,
>
>I'm confused. Are you sure that the higher readings at various measuring
>sites in the winter weren't due to improved efficiency of the transmitting
>antenna (a local effect) and had little to do with the soil conductivity in
>the far field?
>
>Bill A
>
>> >some
>> > broadcast engineers attempting to measure soil conductivity in the AM
>>band
>> > by means of signal attenuation noted that their conductivity results
>>came
>> > out on the high side during very cold winters.
>>
>>Amen. The difference can be impressive. Over the lousy ground here in the
>>Northeast, smart AM guys see that their initial field strength
measurements
>>are made in the winter. That way, when the FCC sets the limits on their FS
>>monitoring points, the station should be safely under them all year.
>>
>>That said, AM field readings can vary dramatically with temperature over a
>>time frame that's much too short to be explained by the ground, trees, or
>>anything but the air. I've never seen a convincing explanation of that
>>effect. But I've observed days in January where the weather was balmy in
>>the
>>morning and very cold in the afternoon following a frontal passage, and
>>local AM field readings went right up with the temperature.
>>
>>John A.
>>
>>
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