[Amps] Amp output power

[Roger (K8RI)]

The early datasheets showed larger figures than the later ones.  Yes, I 
believe the derating was a political move to make the FCC happy<:-)
Just remember when running near maximum ratings and particularly grid 
ratings on fragile tubes, that tune and load control adjustments are 
small and careful.  A tiny excursion into over drive due to moving the 
load control too far can quickly destroy a tube. With over drive 
protection and careful tuning, the tube can be run on the edge and last 
for years.

It's a good idea to have sensitive and quick acting over drive protection.

For those who call the 3CX800 small, take a look at the 3CX400/8874.  
Then look at the price.  No wonder so many are converted to 3CX800A7s or 
3CPX800A7s

73

Roger  (K8RI)


On 8/24/2015 5:31 PM, Steve Thompson wrote:
> If you check at
> http://www.g8wrb.org/triodes/
>
> there's several data sheets. I came across a copy of the one with 
> 1370W output spec. and copied it to David to host. I believe there was 
> a spell where FCC applied rules relating to output power spec. of the 
> devices in a transmitter, hence the 750W rating appearing so a pair 
> was valid for a 1500W amplifier.
>
> I think the same applied in the case of Svetlana 4CX800A data.
>
> Steve
>
>> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>>
>> On Sun, 23 Aug 2015 18:25:38 -0700, Jim wrote:
>>
>>>
>>> The non-pulse rated 3cx800 max ratings are 2250V plate voltage, 0.6
>>> plate amps. Typical operation at 2200V and 0.5A with 23W of drive will
>>> get you 750W AB2 output.
>>
>> REPLY:
>>
>> That's interesting. At 2250 VDC and .6 amps, the DC input is only 1350
>> watts. At 60% efficiency, the RF output would be 810 watts and the
>> plate dissipation would be 540 watts.
>>
>> The tube's rated plate dissipation is 800 watts, yet in class AB with
>> max Vp and Ip, you come nowhere near that rating. Most tubes will put
>> out RF well in excess of their dissipation rating. For example, a
>> 3-500Z with only 500 watts plate dissipation will put out 750 watts
>> and still be within ratings.
>>
>> The question is, why would a tube have such a high dissipation rating
>> if it is not capable of reaching that in normal class AB operation?
>> Perhaps it is intended for use in class A?
>>
>> Seems strange to me. Your thoughts?
>>
>> 73, Bill W6WRT
>
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