SV: SV: [AMPS] Re: SV: G2DAF

[Rich Measures]

>
>
>
>G3SEK:
>
>>>Yes, please send me a copy, Lars.
>>>
>>>Can you also say what tube, what anode voltage, and how the screen
>>>voltage was generated (voltage doubler/tripler? solid-state rectifiers
>>>or vacuum tubes? Value of DC smoothing capacitor?)
>>>Something tells me that all of these details could be important...
>>>One risk with the G2DAF configuration is that a screen rectifier with
>>>poor efficiency would tempt the user to overdrive the whole amplifier in
>>>order to generate sufficient output. Thus there could be a lot of
>>>variation between a good G2DAF linear and a bad 'un. 
>
>AG6K:
>>There should be little difference if the screen potential is not 
>>constant.  
>
>
>G3SEK:
>>>
>>>The choice of tube could also make a big difference between good and
>>>bad. As far as I know, all the original published work was done with
>>>813s and 4-125s.
>>>
>>813s and 4-125s have screens that follow the 3/2 power law.  
>>
>>>In the late 1960s I had my education about SSB from listening to G2DAF's
>>>80m net, whose members were bitingly critical of poor-quality signals -
>>>so much so that like many other listeners I didn't even dare to check in
>>>for a report! Certainly there were several G2DAF amplifiers in use on
>>>that net, and if they hadn't generated a clean SSB signal the owners
>>>would have been flamed to a crisp after the first transmission.
>>>
>>>Later I met Dick Thornley a few times, heard him talk to clubs, and saw
>>>his construction work. He was a perfectionist in every detail
>
>AG6K:
>>-  -  except one.
>>
>G3SEK:
>
>>>and he owned his own spectrum analyser which was a real rarity in those 
days.
>>>Certainly he was the first to ask for criticism about his own signal
>>>quality. He also wrote a regular magazine column on SSB techniques when
>>>this was all new, experimental stuff. 
>>>
>>>So I am in two minds about his amplifier. Part of me says "This should
>>>not work." 
>
>AG6K:
>>It isn't that it doesn't work, rather it does not deliver on the 
>>seemingly-miraculous promise of Class-C efficiencies And good linearity.  
>> By supposedly delivering the miraculous, a guy takes on prophet-like 
>>status, whereupon groupie types will symbiotically follow and sing his 
>>praises for crumbs of approval.  .  We see a similar mechanism in 
>>religious cults.  The silent Bhagwan drove a fleet of Rolls Royces whilst 
>>his groupies swooned.  Meanwhile, back at the Rolls Royce dealer in 
>>Seattle, the salesmen said that the Bhagwan had plenty to talk about 
>>during his frequent purchases.  
>>
>G3SEK:
>>>But having been around at that time, and known some of the
>>>people involved, I also feel that G2DAF would not have given his name to
>>>anything that put out a poor-quality signal.
>>>
>AG6K:
>>The G2DAF-amp.  signals I listened to on the air had tolerable distortion 
>>levels on frequency.  The problem was the -22db/-23db adjacent splatter 
>>level when recommended amounts of grid current were being used.  However, 
>>when zero grid current was used, splatter understandably decreased.  
>>After complaints of splatter, I observed that G2DAF proponents would 
>>Temporarily lessen grid current to make peace.  
>>-  later,  Ian
>>
>>Rich...
>>
>SM3BDZ:
>
>Brilliant comments Rich. Somehow I feel Ive read you saying the same 
>things before....
>
  The technical issues do not change.  Not everyone here is familiar with 
the DAF circuit.  .  The groupie-guru element is something I have not 
discussed before on the AMPS group.  

>Pse excuse my bad humour Rich, but here in Sweden we have a special word 
>when cows tjew and tjew and tjew their food over and over again. I dont know 
the
> english word for 
>that syndrom, but somehow - cant help it- it gives me associations to your 
>argumental technique....;)

In English, the word is chew.  One saying goes:  "I don't chew my bread 
twice".  
>
>If you have two doors to your house, I´m quite sure that you have never 
>ever used more than one and perhaps
>cant even find the other door ...

There are three doors for humans to this house.  I use all three.  The 
cats have their own door so that they can hopefully avoid becoming dinner 
at Mr. and Mrs. Coyote's place.  

>- cause you dont bother to look.....
>
>Absolutely nothing personal Rich, I´m just not that good to express 
>myself....
>
You are doing rather well.  

>By the way, any comment you want to share with us regarding the plots I 
>sent you last x-mas?
>
no
>
-  later, Lars


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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