[600MRG] Amp

[kl7aj at acsalaska.net]

Your mileage may vary here:

When I was working at HIPAS, we had an experimental VLF setup for some 
data exchange.  We used a loaded 30 foot vertical driven directly with 
a pulse generator.  The Q of the antenna (in the 180kHz range, as I 
recall) was so high that it was a pure sine wave being emitted from the 
antenna.  I would imagine tthat 90% of the antennas used on this 
experiment would exhibit the same properties!   Of couse you want to 
check it out, but I think you'll see the same thing. 

Eric

On Mon, 3 Aug 2015 14:55:11 -0500, John Langridge <kb5njd at gmail.com> wrote:
> 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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