>From the site....
This is a basic comparison of the GS-35B and the 3CX1500A7/8877. This
information is to be used for making up your own mind about which tube is
for you .
"I don't make any claims about the accuracy or source of any of this data".
Kinda says it all I think.
73
Jim W7RY
----- Original Message -----
From: "kd4e" <doc@kd4e.com>
To: <rfamplifiers@yahoogroups.com>
Cc: "Amps reflector" <amps@contesting.com>
Sent: Thursday, December 17, 2009 8:24 PM
Subject: Re: [Amps] [rfamplifiers] Question about GS-35b efficiency
> When I incorrectly imagined myself capable of building an
> amp like this I discovered this site:
> http://gs35b.com/gs35bvs8877.html
>
> It contains an excellent charted and textually-described
> explanation of the specs and practical applications of the
> two - as well as a compare and contrast of the tubes.
>
> Although the 8877 has higher "mu" it has a lower tolerance
> for error.
>
> I seem to also recall that tuned-circuit components that
> work well with an 8877 may not function as efficiently with
> s GS-35b due to different inductance and capacitance factors.
>
> Of course I am the least-informed and experienced here ...
> so please consider the link without my commentary and see
> what the gathered wisdom here has to offer from their
> hands-on experience!
>
> 73, doc KD4E
>
> And, in case I forget, a blessed CHRIST-mas to all!
>
>> I have a question about the plate efficiency of a GS-35b amplifier.
>>
>> I have built two of them for 160-10 meters, and while they worked ok, the
>> efficiency was not as good as I expected. In both cases I ran them at 3
>> kVDC and
>> in order to get a full 1500 watts out, had to drive them to 1000 mA plate
>> current. That equates to about 50% efficiency, which seemed a bit low.
>>
>> In both cases, I removed the GS-35b and replaced it with an 8877. With
>> no other
>> changes except bias diode and heater transformer, I was able to get 1500
>> watts
>> out with only 830 mA plate current, an efficiency of 60%. I swapped two
>> different GS-35b's with the same result. Both were brand new tubes.
>> Results were
>> essentially the same on all bands, with a slight drop off on 15 and 10
>> meters
>> with all three tubes.
>>
>> With all of the different tubes, I set the bias for a ZSAC of about 200
>> mA.
>>
>> I have spoken to two European hams and one US ham and they have reported
>> similar
>> results.I wonder if the GS-35b might achieve higher efficiency at higher
>> plate
>> voltages?
>>
>> I would appreciate hearing from anyone who has made similar measurements.
>>
>> 73, Bill W6WRT
>>
>> __._,_.___
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>
> --
>
> Thanks! & 73, doc, KD4E
> FS/Swap/Wanted: http://kd4e.com/swapn.html
> Free OS : http://www.PuppyLinux.com
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