[Amps] 833 amp

[Carl]

The 833 is still a popular tube with the AM crowd 160-40M but usually Class 
C plate modulated. It was used in many BCB transmitters in the 500-1000W 
range.

As an AM linear the carrier efficiency will only be around 33% so Id advise 
a decent airflow from a muffin fan or two that will reach all the tube pins. 
The PEP efficiency will be in the 60% area so that remaining 40% loss has to 
be factored in to the total tube dissipation which can be up to 450W with 
air cooling in ICAS service.

Obviously, Class C is a lot more efficient and an easy 1000-1500W of carrier 
can be generated with one tube and air cooled. Naturally cooled the ratings 
drop considerably.

Carl
KM1H


----- Original Message ----- 
From: "John Lyles" <jtml at losalamos.com>
To: <amps at contesting.com>
Sent: Wednesday, March 17, 2010 1:44 AM
Subject: [Amps] 833 amp


>
> The 833, while magnificant looking for a glass tube, sort of industrial
> 1940s look, was not a particularly high frequency tube. You would have
> troubles making it play at 10 meters, for instance. Neutralization will
> be needed in all cases on HF, and will need to work on reducing the lead
> inductance to the grid and filaments. But for 160 meters, it would work
> fine. Bob Henry in Albuquerque, NM, built a single 833 amplifier few
> years ago, I need to find his email. He had some troubles getting gain
> or efficiency very high, if I am not mistaken.
>
>
>> Message: 3
>> Date: Tue, 16 Mar 2010 14:18:43 -0400
>> From: Greg Weinfurtner <weinfurt at ohio.edu>
>> Subject: [Amps] Building 833 Amplifier. Hints and Suggestions?
>
> .....
>>
>>          I would prefer help from someone who has actually used the 833 
>> in
>> some type of RF circuit.  But anyone with engineering experience with a
>> behemoth of this type knowledge would be great!  I plan to set up a web
>> page and with my progress to keep those helping informed of my 
>> advancement
>> into the past!
>>
>> Characteristics for the 833A are
>> at:  http://oak.cats.ohiou.edu/~weinfurt/833A.pdf
>>
>> ************************************************************************************
>> Plan.
>>
>> 1 Two of them in parallel or Push-Pull?
> RAYTHEON RAN THEM IN P-P ON MEDIUM WAVE IN THE RA-1000.
> MOST OTHER BC RIGS USE TWO IN PARALLEL FOR A KW. AGAIN, THIS WAS AT <1.6
> MHz.
>
>
>> 2 Grid driven with a 55 ohm, 75 watt non-inductive resistor to ground.
> PICK A CLASS OF OPERATION, LIKE B? YOU WILL PROBABLY WANT SOME Q ON THE
> INPUT TO SMOOTH OUT THE GRID
> CURRENT AFFECTS DURING PART OF THE RF SWING.
>
>
>> 3 Pi output network or Pi L ? Or Link coupled output?
> WHATEVER YOU LIKE
>
>> 4 Operation is CW and occasionally SSB. Bias voltage on Cathode developed
>> across about 60v Zener to ground?
> EITHER OK.
>
>
>> 5 Power supply is capable of 3000 VDC at 1 Amp.
> GOOD VALUES, SIMILAR TO BROADCAST RIGS
>
>> 6 Forced air cooling up from pressurized bottom chassis to box on top
>> housing tubes and output components.
> YES, GOOD IDEA
>> 7 Tubes mounted in vertical position. Heat sinks for pin connections.
>
> ABSOLUTELY.
>>
>>
>> Greg Weinfurtner AEE BSS
>>
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