Re: [Amps] Electronic bias circuit shematic

[Vic K2VCO <k2vco.vic@gmail.com>]

I don't like the idea of RF-operated EBS systems because it seems to me very hard to avoid 
distortion at the beginning of a CW character or syllable when the system first opens. 
What I have done in my last few projects is to drop the bias from cutoff to operating 
level along with the t/r switching of the QSK/VOX system. Since there must be a few ms 
delay built into this circuit before and after the start of RF, there is plenty of time 
for the bias to change.
I don't see how an RF operated system can have any advantage over this, and it is much 
simpler -- it can be done with a couple of transistors or a reed relay.
On 6/27/2013 6:55 AM, Branko Cehner wrote:
> Hi,
>
>   
>
> I have new home made tetrode QRO with GU77b tube using tetrode board from
> G3SEK. The resting current on TX at -65V on G1 is about 350mA at 2,3kV which
> is about 800W of wasted power, so I  think the usage of  2 or 3 state EBS
> will much reduce wasted power.
>
>   
>
> I was googling the web, but haven't find much of shematics about that. Does
> anyone have some nice shematic? I saw the W8JI EBS-1 analyze but I'm not
> shure the shematic is complete and is just for analyze purpuse.
>
>   
>
> I have read on some pages, slow EBS circuit can boost the splatters and
> lower the quality of SSB singnal, so I look for design which won't do that.
>
>   
>
> The Ameritron sells EBS-1 kit for Ameritron amplifiers (no shematic on web),
> but I'm not shure if it works with so low G1 bias as in my hiome made QRO
> (the bias of 572 tubes or 3-500Z or even 3cx1500 are quite away from -65V I
> use).
>
>   
>
> So sny good information?
>
>   
>
> Best regards, Branko, S52V
>
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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