You stole my thunder, Ian. Yuri and Rich seem to be
agreeing with each other about two totally different
things. What Rich was talking about is path loss that
varies as a function of EIRP. In my opinion, this is a
very questionable thesis given the amount of power
involved (even 10dB above the legal limit in the US is
a drop in the bucket - remember we are talking about
microwatts/meter^2 whereas the old sol is in range
of KW's/meter^2). Yuri seems to be making the claim
that path loss can be a highly variable function of
location, antenna height, frequency, local terrain, the
ionosphere, the neutral atmosphere, etc. I certainly
hope nobody is disputing that. If they are then they
haven't been on the air very much :):)
In regards to Rich's observations, we need to be
asking several important questions:
1). Was there any time constant associated with this
"non-linear" phenomenon? If for instance the time
constant of the non-linear effect is faster than say 10mS,
then one could expect it to generate IMD products as
the non-linearity would be within the audio bandwidth of
an SSB transmitter.
2). What experimental protocol did Rich and his fellow
observers use to control for fading? Calibrated S-meters
alone aren't sufficient to control for fading.
3). What experimental protocol did the 8171 owner use
to ensure that his power gain was really 20.0dB. Old
measurements that Rich made in his lab wouldn't
necessarily be valid as the new owner's setup could
easily have added 3dB of uncertainty.
73 de Mike, W4EF.........................................
----- Original Message -----
From: "Ian White G3SEK" <G3SEK@ifwtech.co.uk>
To: <amps@contesting.com>
Sent: Sunday, February 06, 2005 3:30 PM
Subject: Re: [Amps] 10dB and propagation
> Yuri wrote:
> >You guys might try to poke fun at this. But there are many factors
> >contributing to signal levels received at the other end. Antenna
> >pattern, local ground conditions, terrain and propagation conditions.
> >VHFers know about ducting on VHF between W6 and KH6, you drive up the
> >hill and you can find spot where your signal (few watts) will hit it
> >and you QSO with KH6. You go few hundred feet up or down and you lose it.
> >
> Sure, all of that is true... but it all goes strictly dB for dB. There
> is no support for tropo ducts behaving in a non-linear fashion.
>
> Let's not confuse the variable *importance* of a dB under different
> circumstances (which is obviously true) with any suggestion that the
> propagation medium itself is non-linear.
>
> A non-linear medium would have to mean that your signal was directly
> affecting the ionization density or the refractive index of the
> troposphere. As I already said, that's wishful thinking at amateur power
> levels.
>
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