SV: [AMPS] Tetrode Amp Help

[sm5ki]

Hej!

Do you really need a stabilized screen grid supply? If the g2 voltage
follows relatively slowly the envelope of a SSB signal, you should get a
only a slow gain variation in the tube??? You have then to use a large
condenser across the g2 voltage. If I remember right ( and I may be wrong
)looking into the NAG gg two meter 4CX350 linear  the g2 voltage adjusted
itself to the average drive level and you could use anything from 3-10 watts
of drive with good linearity.I used the famous IC 202 as a very clean driver
- the linear supplied the 13.5 VDC. 

>From Hans / SM5KI new member of the RSGB Ian
----------
>Från: "Ian White, G3SEK" <G3SEK@ifwtech.demon.co.uk>
>Till: amps@contesting.com
>Ämne: Re: [AMPS] Tetrode Amp Help
>Datum: tor 9 dec 1999 08.53
>

>
>Leigh wrote:
>>
>>I guess the biggest question I have is in regards to the 
>>requirements of the screen supply.  There appears to be no screen 
>>by-pass resistor in the RF deck so I'll assume the builder (have 
>>no idea who it was) included that in his screen supply.  The 
>>Eimac data sheet states 70mA for this resistor so I guess its 
>>value should be around 5k ohms?  What is the recommended size of 
>>this component.  I would guess 5 watt would be large enough but 
>>maybe I am not considering possible failure modes?  Some 
>>references I have seen state that HV should be applied before the 
>>screen voltage so I'll assume it is a good idea to apply screen 
>>voltage with the TR relay activated.  Any thoughts on a 
>>recommended screen supply circuit.  I wouldn't think with the 
>>screen bleeder that regulation is required and I was thinking of 
>>using a choke input filter (anyone have a ~4-5 HY 350mA 400VDC 
>>filter choke lying around?).  
>>
>The Eimac advice assumes that you are not using a regulated screen
>supply, only a "dumb" bleed resistor - but for good linearity and tube
>protection you MUST regulate the screen voltage closely. 
>
>When you use active regulation of the screen voltage, you no longer need
>a 70mA bleed. 10mA is plenty, and its only function is to clamp the
>screen voltage while the T/R relay contacts are actually changing over.
>
>There is a QEX article on screen supplies, downloadable from my web
>site: http://www.ifwtech.demon.co.uk/g3sek/boards/tetrode/tetrode-3.htm
>
>
>73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
>                          'In Practice' columnist for RadCom (RSGB)
>                           http://www.ifwtech.demon.co.uk/g3sek
>
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