[NLRS] Is there published data on tree foliage ...

[Dr. Gerald N. Johnson]

On 7/11/2014 8:36 AM, Chris Elmquist wrote:
>
>
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> How would a guy "visualize" multi-path on an ATSC signal?  It seems to
> me like you could only see it after detection right?   There's no way
> to see it in the RF domain with a spectrum analyzer for example.

You might be able to detect it as phase jumps in the discrete carrier 
component of the ATSC signal. That would take a good local reference or 
a delay line a few wavelengths long then comparing the delayed signal 
with the direct signal.
>
> I'm dreaming of some kind of monitor scope that would show two spikes
> moving around closer and farther apart as the path delay changes--
> as the wind blows, as the leaves get wet, etc.

I don't think the effect is one of these so much if the signal is 
monopath. Some slow phase changes are tolerated, providing all the data 
has the same phase reference. What really messes the detector up is when 
the strongest signal changes from one path to another because of wind, 
moving leaves, a moving van on the road, that abrupt change upsets the 
detector more.

My converter box has both signal strength and quality indications. On 
some weak signals it can show 50% signal and zero quality. When changing 
from a working channel to one its not successfully decoding, it often 
will show signal strength and quality that it was decoding but in a few 
seconds quality goes to zero, all the time after the channel change its 
not putting out picture or audio. It might be that had I an owner's 
manual it would explain the significance of these indications. I picked 
it up in a thrift shop with no documentation.
>
> Chris N0JCF
>
73, Jerry, K0CQ