[600MRG] Amp

[John Langridge]

>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, you make a really good point here... Taking it a few steps further.

While the engineer will want to optimize ad infinitum, at the end of the
day its going to be a mountain out a mole hill because few stations will
actually be loud enough on a consistent basis to be a real issue.  And
thats another point that has been made time and time again over the years
on the topband reflector.  While key clicks can impact anyone, the most
egregious offenders are the ones that are the loudest...  right or wrong to
ignore?  that's a different question entirely...

I've never heard anyone with key clicks on 630m after being on the air just
about every night since 2012... and its not because there is no CW
running... its because signals are either sufficiently weak that the clicks
are not heard or they are not present.

73,

john




On Mon, Aug 3, 2015 at 2:40 PM, Kenneth G. Gordon <kgordon2006 at frontier.com>
wrote:

> 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
>
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