Re: [Amps] 10dB and propagation

[R.Measures <r@somis.org>]

On Feb 8, 2005, at 9:56 AM, Michael Tope wrote:

> ----- Original Message -----
> From: "R.Measures" <r@somis.org>
>
> >   Some mornings, 20db more Tx suds produced 20db more Rx signal and on
> > other mornings, 20db more Tx would make c. 23db more Rx signal.  There
> > appeared to be no way of controlling anything.  It was: what you see 
> > is
> > what you got, and you can't change it a jot.
>
> So what you are saying is that at one instant with the
> 8171 off the signal was S-xx and then in the next instant
> (e.g. in the span of a few seconds) the operator turned
> on the 8171, and the Rx signal went up by 23dB even
> though the increase in tx power in that same instant
> was only 20dB?

Correct, and it was repeatedly repeated to factor out the QSB factor.

> That would imply that the ionospheric
> plasma heating due to the 8171 output was almost
> instantaneous.

Agreed.  It was fast and not predictable.

> If that were true, I would expect that the
> thermal conditioning of the plasma could follow the
> syllabic envelope thereby causing distortion.

My take on the phenomenon is that it was not thermal or there would 
have been a lag time.  My guess is that the ionosphere's electrons were 
on the threshhold of jumping up to the next orbit and the extra energy 
gave them a push.

> And if 16KW PEP to a dipole would cause 3dB distortion,
> the just imagine how bad a foreign broadcast station
> would sound running AM with 500 KW to a curtain
> array.

Foreign broadcast near the 40m and 80m bands during the daytime is a 
different subject.  This condition was observed only after sunrise 
between adjacent Western states, so the D-layer was a factor.

> If the thermal conditioning were a bit too slow to
> follow the syllabic envelope, then you would be able to
> see some droop on the RX audio output (w/agc off) if you
> pulse modulated the 8171 exciter between say 1 watts
> and 100 watts with a 50% duty cycle square wave.
>
> Anyway, I don't have a stiff enough service drop to
> run an 8171, so I guess I don't need to worry about all
> this :)

I ran mine from a 100A service with .075-ohms of ESR, but I tuned up 
the sucker with a tuning pulder.

cheerz, Mike.
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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