[TowerTalk] Fwd: Tower and antenna decisions

[Jim Lux]

On 10/26/13 8:15 PM, Hans Hammarquist wrote:
> All these "modern", solid state, PA have the same problem, they are "protected" and the "protection" rolls back the power as soon as they detect reflected power. Little depending on make and design they roll back more or less. That's why the manufacturer offer built in tuners. The "old days" with a pi-filter on the output could be tuned to most anything below SWR of 1:3 or even more, and they didn't have (needed maybe) the "protection". As long as you didn't kill the final tubes by overheating them, you were OK. Do we like to have the "old" tube final back? Maybe.
>

I would rather have "smart antennas" with the finals *at the antenna* 
and the matching done there.

Sure, it's more complex than the historic Transmitter in 
Shack/Feedline/Fixed Antenna, but life moves on.

For instance, I sketched out an interesting design for a form of Yagi 
with all driven elements, using an array of magnetic loops, rather than 
the traditional horizontal elements. The matching from low Z 
semiconductors to the low Z of the magnetic loop is actually kind of 
what you want.   And you're doing spatial combining, so with 5 elements, 
each driven with a 200W module, you don't have the losses in the power 
combiner you see in a "single output" SSPA.


Combine this with things like polar modulation, and you can get some 
very interesting designs. It's almost like having the entire rig at the 
top of the tower, and all you need is power and an ethernet link, which 
could be wireless.

Sure, its nothing like ham radio in the past, but that's what ham radio 
is all about: try new things.