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@yahoo.com>
>> Subject: Re: [Amps] plate dissipation and duty factor
>> To: jtml@vla.com
>> Cc: amps@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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