[Amps] 10dB and propagation

[Michael Tope]

---- Original Message ----- 
From: "R.Measures" <r at somis.org>

> 
> On Feb 6, 2005, at 6:09 PM, Michael Tope wrote:
> 
> > 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).
> 
> Mike -- Which is why I was originally skeptical.   However, the 
> Stanford Research Institute's ionospheric project used 8171 amplifiers.
> 

Did they publish any papers on this phenomenon?

> > 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.
> 
> The time constant was long and was seemingly related to sun angle and 
> serendippity.

What do you mean by long - seconds, minutes, hours?

And by time constant do you mean to say that at the first instant of 
comparison, the instantaneous on/off ratio of the 8171 was 20dB, 
but as you worked the frequency harder, the instantaneous on/off 
ratio changed to 23dB?

In other words did the instantaneous on/off ratio of the 8171 change
as a function of exposure time?

> > 3). What experimental protocol did the 8171 owner use
> > to ensure that his power gain was really 20.0dB.
> 
> The V-gain was x 10.
> >
> > 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.
> 
> Not likely because the mains-V was 240v +/- 5% at both sites and no 
> change had been made in the anode or screen supplies.  I measured 
> 1200V-pk output into 50-ohms (14kW), and my guess is that adding 3db 
> (28kW) was not do-able short of going to an 8281 (4cx15.....), a more 
> capable anode supply, and most likely a 200a mains service.
> >

What about load VSWR? Did his antenna VSWR match 
the input VSWR of the 8171 amplifier? If not, then his 
on/off ratio could have easily differed from one you 
measured under different conditions. And was the tuning
of the 8171 fixed. If not, he may have adjusted the tuning
differently than you did (another source of possible error). 

73 de Mike, W4EF..................................