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Re: [Amps] 4CX250B Ratings in Dentron Clipperton V

To: "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] 4CX250B Ratings in Dentron Clipperton V
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
Date: Sun, 23 May 2010 18:16:49 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Your are right. I need to put my glasses on next time. However, I believe in 
this case the target is getting max output with out much regard to IMD. 
Another bit of confusion, 50 watts idle dissipation in a 65 watt plate 
dissipation tube sounds far from class B operation. Should be AB2. 
These were used in the PRC47 transceivers but only at around 100 watts output. 
I wonder where they were used for 300 watts output SSB suppressed carrier?

73
Bill wa4lav

________________________________________
From: Carl [km1h@jeremy.mv.com]
Sent: Sunday, May 23, 2010 3:52 PM
To: Fuqua, Bill L; amps@contesting.com
Subject: Re: [Amps] 4CX250B Ratings in Dentron Clipperton V

And if you read further it also says for SSSC to adjust the bias for 50W
plate dissipation.

Carl
KM1H




> Now here is an example of a tube operating at max output with out regard
> to IMD products. I expect this spec. was intended for mobile or portable
> military radios where power and compactness is more important than
> splatter. Look at the Class B operation of the 4-65A at 325 watts PEP
> output. A note recommends adjusting the control grid bias for ZERO plate
> current.
> http://frank.pocnet.net/sheets/088/4/4-65A.pdf
>
>
> 73
> Bill wa4lav
>
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf
> Of jonathan white [jonathan.white20@btinternet.com]
> Sent: Sunday, May 23, 2010 7:05 AM
> To: amps@contesting.com
> Subject: Re: [Amps] 4CX250B Ratings in Dentron Clipperton V
>
> On 23/05/10 09:10, Ian White GM3SEK wrote:
>> Dick Hanson wrote:
>>
>>> Unfortunately, however, we're sort applying lipstick to a pig here. The
>>> 250B is just not a very 'worthy' tube at -22db; hard to gain BFF among
>>> your neighboring six meter guys..... Might as well run an old model
>>> brick with no active bias (closer to class C than AB anything).
>>>
>>>
>> At output levels of about 250W PEP per tube, the 4CX250B is capable of
>> IMD3 figures around -35dB (referenced to PEP).
>>
>> It is Eimac's marketing claims, inciting users to drive the tubes to a
>> much higher power output, that were "unworthy"... not the tube itself.
>>
>>
>>
> I agree with you Ian, 25yrs back,there was some outrageous signals on
> 2mtrs with overdriven `250b`s poor regulation of screen supply, poor
> anode supply and zenner diode stacks feeding screen.
> Also the QQVO6-40a was another valve that suffered that treatment.A
> German outfit was making single valve QQVO6-40a with 100w PEP out,and a
> `4CX350b at approaching 500w .A local station 2miles was producing
> splatter  across  most of the band and that was with the antennas
> disconnected and I never used a masthead preamp.
> I think this is were Mr Nelson stepped in.
> PS I used a 6-40a driven to 40w PEP, into a Cushcraft Boomer, the WMD of
> the day!
> Regards
> Jon G8CCL
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