[Amps] Defining CCS

[Manfred Mornhinweg]

I wonder why we are even discussing all this CCS versus ICAS stuff here. 
We are radio amateurs, right? Not broadcasters. I fail to see what's the 
sense of having a CCS amplifier for our ham use!

Let's see reality: Most hams only engage in occasional operation at less 
than 50% TX time, with TX no longer than a few minutes at a time, and 
mostly in reduced duty cycle modes such as SSB or telegraphy. That's 
extremely light duty, and hams doing only this can get away perfectly 
well with low cost amplifiers built for that sort of service.

Of course that's not good enough for every ham. So, what's really the 
most demanding use hams have for their amplifiers? What comes to mind is:

- RTTY operation, at 100% duty cycle during TX, and maybe a 70/30 ratio 
of TX/RX during CQ calling. That's far more severe use than SSB 
chatting, but still far from CCS. And RTTY doesn't require a LINEAR 
amplifier, so it would be very reasonable to switch an amplifier into 
non-linear class C operation for RTTY, or at least run it in saturated 
class AB (many hams do that!), to reduce loss and dissipation.

- RTTY contesting: It's the same as above, but typically over 48 hours. 
It's still not CCS.

- RTTY bulletin transmission: That can be 30 minutes of full power 
operation. It's still not CCS, because operation isn't 24/7, but starts 
coming close, in the sense that after 30 minutes at full power an 
amplifier probably has reached its thermal plateau. This kind of 
operation is NOT normal ham operation, though, but is what only a very 
few stations do, such as W1AW.

- The cat falling asleep on the key: That's an act of negligence, and a 
ham leaving his amplifier on when walking away for a long time deserves 
amplifier failure as fair punishment for creating sleeping-cat-QRM. Even 
so, a good amplifier should include thermal protection, and in that case 
it would shut down a while after the cat falls asleep, preventing 
damage. It still doesn't need to be CCS-rated.

The only ham application that I can think of, that comes close to CCS, 
is repeaters. Again not a normal ham station.

So, can anyone give a good reason why a CCS amplifier might be desirable 
in a ham station, other than for bragging? As far as I can see, an ICAS 
amplifier that allows enough duty cycle for the most demanding kind of 
operation done at that station is a better solution than a much more 
expensive, heavier, larger CCS amplifier that will never be used to its 
full capability.

The anecdote of Alpha using 60 WPM dits to make people believe their 
amplifier can run CCS is funny. Probably most hams visiting that booth 
bought the story... Like they buy the story told by certain videos on 
Youtube and manufacturer's websites demonstrating "undestructible" 
LDMOSFETs while driving them at 10% duty cycle. The cheating here is in 
telling people, or at least insinuating, that the actual duty cycle is 
100%, when it isn't. But 60 WPM dits indeed is a reasonably good 
simulation of the kind of duty cycle an amp will see in a ham station 
during the most demanding types of operation, and the 10% duty cycle 
pulses uses by some LDMOSFET makers is also quite representative for 
many of their intended applications. So the cheating isn't in the way 
the demonstration is done, but in misrepresenting what the exact 
operation conditions are.

Manfred

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