[RTTY] Heathkit SB-1000 On RTTY

[Joe Subich, W4TV]

 >>   By definition PEP can't be 100% duty cycle.
 >
 > REPLY:
> Of course it can. You are confusing duty cycle with average power
> output.

OK, make that 100% duty cycle at full output.  Once you add a PEP
qualifier you're derating the tube ... or you're at least implicitly
saying this is not a constant carrier application.  There is a *big*
difference between 100% duty cycle in FM or RTTY service and 100% duty
cycle in unprocessed SSB service.

Eimac's data sheet said 400 mA CW or PEP - in other words, non-constant 
input/output.  It also says 280 mA "two tone plate current" - in other
words, average over time.  Eimac also rates the 3-500Z at 275 mA plate
current and 330 W plate dissipation for "carrier conditions" in plate
modulated class C service.

I'd suggest the "carrier conditions" rating is the most appropriate for
RTTY.  With 275-280 mA at 2500V in AB2 one is still looking at a safe
limit of about 400W from a single 3-500.

73,

    ... Joe, W4TV


On 9/24/2012 11:12 PM, Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
> On Mon, 24 Sep 2012 22:27:20 -0400, W4TV wrote:
>
>>   By definition PEP can't be 100% duty cycle.
>
> REPLY:
> Of course it can. You are confusing duty cycle with average power output.
>
> A two tone test signal with a certain PEP broadcast continuously is 100% duty
> cycle.  The same two tone broadcast in an equal on/off manner would be 50% duty
> cycle. The PEP is the same but the duty cycle is different.
>
>>From Google definitions: "The cycle of operation of a machine or other device
> that operates intermittently rather than continuously".
>
> For example if you transmit SSB voice continuously you are doing SSB at 100%
> duty cycle. If you transmit SSB voice for ten seconds, listen for ten seconds
> and then repeat over and over, you are doing SSB at 50% duty cycle.
>
> 73, Bill W6WRT
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