From: MarkusVester@aol.com
Message-ID: <d8.16b878b3.29f73f07@aol.com>
Date: Tue, 23 Apr 2002 18:49:43 EDT
Subject: Re: LF: Jason recording session
To: rsgb_lf_group@blacksheep.org
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Hi Wolf, Jim, Stewart and LF group,

mni tnx (also to Alberto!) for the enjoyable QSO and Jason tests. As I hadn't 
read about the sched on this reflector before, I sort of stumbled in when I 
heard Jim asking for lower power Jason.

> Markus used his linear TX with an output power between 130 W down to 
> 100 mW. 

The first two steps of the power reduction were done in an improvised manner 
by loosening the inductive coupling to the antenna variometer, which presents 
a higher load impedance to the PA and preserves its efficiency. In the 
beginning, I had some trouble with my automatic antenna tuner: Apparently, 
the sharper antenna resonance produced more gain in the phase detector servo 
loop, resulting in oscillation of the variometer and calling for a 
(literally) hands-on solution. Stewart may possibly detect some low-level 3 
Hz sidebands... The even lower powers were generated by additionally 
modifying the PA's duty cycle, aided by a scope coupled to the antenna for 
relative amplitude calibration. The step from 1 W to 0.1 W was in the middle 
of the last Jason transmission.

>  I don't know what Markus' lowest ERP was when Jim had still fair copy - he 
>  may explain himself.

The efficiency of the antenna is about 8*10^-4, so 1 W results in 0.8mW EMRP 
or 1.5 mW EDRP.

>  it seems my old laptop is not suitable for this - Windoze asked me to 
close 
>  the application which occupied the soundcard, and a second PC was not 
>  available during the test.

...same here. Without AC97, I guess we have to resort to a-posteriori 
decoding.
  
>  Thanks for the test to everyone involved. Jim told us he will be putting 
out 
>  a Jason signal tomorrow, maybe something to listen for across the pond if 
he 
>  uses full power ?

Perhaps with a lot of luck, as condx seem a little unfavorable presently. Had 
a spectrogram running last night and most of today, to evaluate what looks 
like CFH's idle carrier on 137029. Nighttime levels were consistent at a very 
moderate level around 4 dBuV/m (compared to good nights peaking in the 30 to 
40 dBuV/m range), but then on the other hand it was visible all day, down at 
-15...-10 dBuV/m.
 
Best 73 
Markus, DF6NM