[Amps] Choosing a Plate Transformer

[Jeff Blaine]

Hi Scott,

Right.  The total power drawn must equal the total power input.  So a 
doubler needs 2x the current (on average) in exchange for the magic of 
doubling. 

And consider that the plate voltage loaded will drop 5-15% from idle in 
your calculations.  Meaning a 900v tx will give you something in the 
2200-2300v loaded (depending on tx capability).

I would lean heavily on the more rather than less in the tx capacity, if 
you have the room.  Depending on amp efficiency, the GI7B will really 
rock at the higher voltage and as long as the plate dis and grid drive 
is kept under max limits, the output is unbeleivalbe in some cases on 
the lower bands especially.

Good luck!

73/jeff/ac0c

KB0NLY wrote:
> I'm thinking about slowly scrounging parts to build another amp in the future, it will be a ways off so in no hurry, and i was wondering how one chooses a plate transformer.
>
> I know the minimum i'm shooting for, 2500v 600mA.  This will be to run a single GI7B.
>
> I was thinking about using those Far Circuit boards for constructing the doubler and rectifier.  It looks like the average factor is 2.8.  Which means for 2500v i would need a transformer with a secondary of at least 893 volts (rounded up).  But what should i do on the current capacity side, should i look for something as high as a 1 amp transformer?  Most of the ones i am finding on eBay for example are 500mA or smaller.  I could probably get away with .500 mA.  
>
> The question is, does one loose ampacity with the double circuit, or does the current remain constant?  I can't seem to find any notes in the handbook articles on the subject of choosing a transformer.  This is why the last amp i built i used a donor FL-2100B so i wouldn't have all the questions on constructing the power supply.  But the next time around i want to build the power supply from scratch and learn more about HV supplies!
>
> The 6M amp i just built is working great by the way.  It will do 500w but i keep it around 400w.  I checked into a net this weekend that a nearby club holds on 6m, they were suprised how loud i was as i'm usually the most distant and sometimes one of the weekest for them to hear.
>
> 73,
>
> Scott KBØNLY
>
> www.kb0nly.net
>
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