Thanks for that further explanation! I'm looking at some transformers, keep
an eye on them to see if they stay within budget, that would suite my needs.
On my 6m amp using the FL-2100B power supply it has a 1A transformer, i get
about 2400V no load. If i drive it with 20w i get 500w output, 400mA on the
plate and 80mA on the grid. So that combo seems to be working pretty good!
That's what i heard also on these tubes, they can be surprising! The higher
plate voltage is better, i would like to shoot for around 2500v on the next
build to create a 2m amp.
73,
Scott KBØNLY
www.kb0nly.net
----- Original Message -----
From: "Jeff Blaine" <keepwalking188@yahoo.com>
To: "KB0NLY" <kb0nly@mchsi.com>
Cc: <amps@contesting.com>
Sent: Tuesday, March 10, 2009 10:49 AM
Subject: Re: [Amps] Choosing a Plate Transformer
> 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
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>>
>
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
>
>
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