[TowerTalk] perspective

[K3BU@aol.com]

In a message dated 7/20/2000 1:21:43 AM Eastern Daylight Time, 
w4ef@pacbell.net writes:

> 
>  What you are saying is completely baffling to me. If the 
>  ionosphere is non-linear as you say, it would cut off the 
>  parts of your signal where the envelope dropped below
>  the minimum required entry threshold. Were you changing 
>  your output power in 1dB increments with a calibrated 
>  attenuator when the reporting station saw 5dB change in 
>  your signal? Was the observing station using a calibrated 
>  attenuator to measure your signal? How did you control 
>  for other variables such as fading? 
>  

No calibrated attenuators, chart recorders or white coats :-)
Just the difference in the station hearing and answering or not under 
marginal conditions.

>  I just don't understand how the ionosphere would know to 
>  pass a large signal into the duct and not a weaker signal? 
>  And if it somehow knows how to do this, how come it doesn't 
>  create intermodulation distortion of SSB signals as the RF 
>  envelope of the signal is modulated thru the "media threshold" 
>  at an audio rate? I mean if you start attenuating your
>  transmit signal, the shape of the wavefronts hitting wouldn't
>  change, only the amplitude of fields would change, but they 
>  would do so proportionally.
>  

Just like if you tried to shine the light from the flashlight at the clouds 
or powerful search light. You would see the light reflection from the 
searchlight, but not from the flashlight. Some make it, some don't. Or you 
can compare gain of antenna to difference between field glasses and 
telescope. Rest is somewhere in between. The trick is getting over the 
threshold of detection of the system TX-antenna-medium-antenna-RX threshold 
(sensitivity, selectivity, internal noise, etc.)
We are familiar with "nonlinearity" of propagation, now you are talking to 
the station 10 over 9, five minutes later he is gone, no trace. 

Yuri

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