[AMPS] Re: Re: New G2DAF amplifier information

[measures]

>
>
>     Well, letīs stick to the QBL5/3500 or letīs try to find another tube
>     that might work in DAF configuration. 

[chortle]

>In my book I consider the
>     QBL quite ok in DAF as I stated before, based upon several amps
>     that I have heard on the air that has the correct bandwith for SSB.
>     Maybe some other tube used in the television service might be
>     sutable, they need very linear and low distortion stuff for TV 
>  service. There are off course the Thompson tubes, TH328 and TH338 but
>     they like the 8877 zero mA grid current fuses.

Say what?

 > There are also bigger
>     Thompsons used like the TH347 but I donīt have any data in my
>     head right now. So letīs rule the 4CX250īs 813īs 4CX1500 out since
>     we pritty much understand that they donīt work in G2DAF.

Who is we?  Do you have a mouse in your pocket?  The 8660/4CX1500B is 
designed to operate with grid-current.  Why would it not work in DAF 
service?

>     By the way, talking about splatter, Yesterday on 21 MHz I heard 
>     a USA station that was 50 kHz wide. 

50kHz is Small potatoes.  W6CHR splattered well over 100KHz with his DAF 
amp.  

> He had monster splatter and
>     wasnīt stronger then 15 - 20 dB over 9. He was runing a IC746 and
>     a amp with GU84īs ( I bet in class C). His call was KG2BU, did anyone
>     of you guys hear him? I of course tried to tell him about his problem
>     but all he responded was "I donīt care", so what to do?
>
A radio homing cruise missile?

later,  Jim--------------------
>
>-----Ursprungligt meddelande-----
>Från:	2@vc.net [SMTP:2@vc.net]
>Skickat:	 den 18 mars 2000 02:08
>Till:	k7fm@teleport.com; Peter_Chadwick@mitel.com; 
>amps@contesting.com; Jan.E.Holm@telia.se; W8JI@contesting.com
>Ämne:	Re: [AMPS] Re:  New G2DAF amplifier information
>
>>
>>Rich said:
>>
>>"Any guesses at to what would happen if a 8660/4CX1500B were used in a 
>DAF
>>circuit. - with say 20mA of grid current instead of 0.06mA of grid 
>current?"
>>
>>Rich:
>>
>>I have heard no one - except you - suggest using an 8660 in a DAF 
>circuit.
>>Your friend, Norm, used 4CX250 tubes in a mis-understood bastard 
>adaptation
>>of the original G2DAF circuit, which hung an electrolytic capacitor on 
>the
>>screen grid.  It splattered badly.  
>
>Norm tried improving the original DAF circuit because it had a tad too 
>much splatter.  
>
>> It was not a G2DAF circuit.  Yet, you
>>use it as a basis to condemn any reasoning that is not consistent with 
>the
>>world as you view it.
>
>I was there.  I got splattered on by the wonderful orig. DAF.  I got 
>splattered on by the modified DAF.  
>>
>>Tubes do not have to be used as the tube manufacturer originally 
>intended
>>them to be used, and amateurs by their very nature are experimenters.  
>I
>>recently built an oscillator which used the screen as the plate.  It 
>works
>>fine.  Tubes were not intended to be used that way.  It is called a 
>Dynatron
>>and was designed long before I was born (which is getting rare these 
>days).
>>Building any circuit - "good" or "bad" - is fine, so long as the 
>builder
>>makes sure he does not unreasonably splatter.  Certain tube design
>>parameters must be met for the long term health of the tube.  Beyond 
>that,
>>the only other question is whether the output has undesireable
>>characteristics such as splatter, harmonics or parasitics.  And, it is 
>up to
>>the designer or builder to achieve those goals.  It would be a boring 
>world
>>if all the amplifiers looked exactly the same and used exactly the same
>>tube.
>
>Running a tetrode to minimize splatter is a piece of cake.  Select one 
>that can do AB1.  (The 813 is not one of them).  Use maximal regulated 
>screen potential and anode supply volts.  Adjust the bias so that there 
>is no grid current with max. drive.  Tweak the screen volts to set Zero 
>Signal Anode Current (ZSAC).  Tune/load for the recommended screen 
>current.  That's All, Folks.  
......

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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