[TowerTalk] Mini Lini on the Tower?

[Jim Lux]

At 11:29 AM 5/16/2005, Rick Karlquist wrote:
>Yes all sorts of problems disappear, but you won't save any money.
>On the contrary, you will spend a lot more money on amplifiers.
>A lot more than you will save on coax, etc.  I thought a lot about
>schemes like this (using *cheap* amplifiers) and I never arrived
>at a scenario that made sense.  Also, running arrays with separate
>amplifiers per antenna specifically is a non-starter if you have
>any mutual coupling between antennas.
>
>Rick N6RK

Mutual coupling doesn't make it exactly a non-starter, but substantially 
more difficult to design and operate than something with passive feed 
networks. How hard depends a LOT on how close the antennas are and what the 
coupling is.  From a practical standpoint, you'll probably wind up having a 
fairly complex matching network on the output of the amp so that it sees 
something close to 50 ohms resistive.

Again, depending on how much superdirective gain you want, you might wind 
up with a lot of excess amplifier capacity.   Taking a simple and 
straightforward example, if you have a linear equal spaced array, the 
maximum directivity will tend to be arrangements where the power is greater 
in the middle of the array. (things like "binomial feed" 1:2:1 power (or 
current) distribution, are an example).

The reduction in overall lost power is, I think, something to 
contemplate.  Much better to have the 1 dB loss in feedline in front of the 
amplifier than after it. It's a dB either way, but in a wallplug to 
radiated power efficiency world, the former is better than the latter.

Of course, in the ham world, it matters not, since transmit power 
efficiency (in a wall plug sense) isn't regulated.

The other thing that would make this MUCH more interesting is when they do 
away with the max gain limit on amplifiers.  As long as you're constrained 
to 10-12 dB gain in a box that puts out reasonable power, it just doesn't 
buy you much to move the amp to the element.  If I could send a few tens of 
milliwatts to the amp module, and still get 500W out. Now THAT would be useful.





>AA6DX - Mark said:
> > Yoo Hoo ..
> > Anybody done any concept brainstorming on the new Class E amp from SGC?  I
> > am quite fascinated with the prospects of using the new SGC Mini-Lini in
> > new applications for HF .. like, mounting the amp on the tower ... simply
> > run an AC cord and use Mini-8 coax up the tower, and all sorts of problems
> > "discapeer" --- like .. RF in the shack reduced, costly coax, coax tower
> > load, xmt loss in feedline (not a factor with this scheme!), etc.
> > For stacks, or fixed EU/JA arrays ... an amp for each antenna ..  as long
> > as not running more than 3 at once, still within power limits ...
> > Since your amp you would be taking on a DXpedition would be so light, you
> > could take MORE ANTENNA .. replacing the amp weight with tower/aluminum!
> > What a concept!
> >
> > I'm still thinking up idears .. mobile, no sweat ... 115VAC from a (these
> > days) inexpensive converter .. already have one that could do that .. and,
> > price of the amp seems like it is going to be SO REASONABLE ...   sure
> > wish I was going to Dayton to see the premier showing.. hopefully this
> > neat new amp will be available this fall .    WoW!
> >
> > Hmmmmm ..........   awaiting the  TT group to share their ideas ...  73,
> > Mark   Eureka, FAR Northern California
> >
> > http://www.sgcworld.com/500watt.html
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
> > Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
> > any questions and ask for Sherman, W2FLA.
> >
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> >
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>any questions and ask for Sherman, W2FLA.
>
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