[Amps] plate dissipation and duty factor

[Roger]

John Lyles wrote:
> If you have a CCS spec for 100 Watts plate dissip (Pd), then don't list plate dissipation going up to 500 watts for unprocessed SSB. Unless you are talking intermittent power to the plate, similar to pulse operation where the peak dissipation is higher than the CCS #. But to prevent misunderstandings, its best to not list a peak plate dissipation, instead give a peak output and an efficiency, from that one can calculate the Pd... I am not certain that voice on SSB is the same as duty factor of short pulses that is readily calculable.
For SSB duty factor should vary with voice characteristics. I would 
guess that there would be at least a 2:1 variance or more at the 
extremes, maybe more.  My voice which is a bit on the coarse side has a 
very high peak to average which means I can use a speech compressor at a 
reasonable setting, gain a fair amount on average power and still sound 
...I was going to say good, but maybe I should say, normal. <:-))

73

Roger (K8RI)
>  If the voice peaks are long, then i would think there would be excessive heating in the anode, if you started out very close to the CCS rating in full carrier, then switched to SSB. Contact Reid Brandon or George Badger, sometimes they read this list. Both have extensive experience with CPI/Eimac products. I am mainly speaking for pulse amplifiers which I work with daily. 
> John 
> K5PRO
>
>
>   
>> Date: Thu, 12 Mar 2009 02:16:41 -0500
>> From: Jeff Blaine <keepwalking188 at yahoo.com>
>> Subject: Re: [Amps] plate dissipation and duty factor
>> To: jtml at vla.com
>> Cc: amps at contesting.com
>>     
>
>   
>> Hi John,
>>
>> Thanks very much for the info.  That's a great bit of data there.  And 
>> it's great to have that confirmation.
>>
>> For the duty cycle, the ARRL if I remember correctly calls out the duty 
>> cycles for unprocessed SSB at 20%, and processed SSB as well as 
>> "conversational" CW both at 40%.  And I want to say that PSK runs about 
>> 70% - something like that.
>>
>> So to combine all this together, let's say that we have a CCS plate dis 
>> spec of 100W.  And assuming the scaling effect (duty cycle vs plate dis) 
>> is completely linear, then that means we should be able to safely run at 
>> these power levels - assuming here that we are only talking about the 
>> tube to simplify the discussion:
>>
>> Mode                     duty cycle      plate dis
>> --------------------------------------------
>> RTTY                        100%          100w
>> PSK (approx)              70%         140w
>> Unprocessed SSB        20%         500w
>> Processed SSB/CW      40%         250w
>>
>> What do you think?
>>
>> 73/jeff/ac0c
>>     
>
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