[600MRG] Amp

[Kenneth G. Gordon]

On 3 Aug 2015 at 15:03, Jim Miller wrote:

> The way I'm thinking about this is the drive to the finals (FETS usually)
> needs to be hard and square at 472khz in order to achieve the desired
> minimum switching transition times.

I'm sorry, but I am not following you: the first question that hits me is "Why?". 
What type of amp are you suggesting? Why does it REQUIRE a 
square-wave input?

> This means the drivers need to hit the
> finals with a 472Khz square wave. Anything less than a square wave at this
> point will result in excessive power dissipation if this is a continuous
> occurrence. Obviously not desirable.

Again, I am not following you here. The amp in question sounds rather odd 
to me.

It sounds to me that rather than an amplifier, you are essentially using a 
switching-power supply to drive an antenna.

> OTOH a finely shaped, e.g, raised cosine (ok, I know its not optimal...) RF
> envelope coming into the amp will have around a 5ms period of rising and falling
> signal. How the predriver, driver and final stages deal with this ramp will
> determine whether or not "key clicks" will result.

ALL amplifiers tend to "sharpen up" the wave-form applied to their inputs. 
Linear amplifiers tend to do this to a lesser extent, but it can still happen with 
them too.
 
> It seems to me that the amp will necessarily sharpen those transitions in
> order to ensure than switching time at 472khz is minimized and therefore
> produce broader CW signals than if a linear was used.

Well, I must again ask, what kind of "amplifier" is this? It sounds rather odd 
to me.

> This should be easy to test on the air. I have a P3 and I'm used to seeing
> "clicky" CW all the time in contests. I usually see a handful of 2-3khz
> signals each time and occasionally a 5khz monster.

Please remember that at HF, at least, clicks can be not only accentuated, but 
even generated, by propagation effects. In my 59 years as a ham, I have 
heard this effect often. I spend most of my ham time on CW.

Ken W7EKB