Topband: Amplifier Help

[Richard (Rick) Karlquist]

Niko Cimbur wrote:
> I first would like to mention that my technical expertise is very limited, and sometimes think I am seeing double. 
> 
> http://www.youtube.com/watch?v=NHdTqnu3sCo&feature=related   (4 minute mark), http://www.om3khe.cq.sk/plugins/diaporama/diaporama.php?lng=en&diapo_id=31
> 
> Can something like this be easily done?  
> I am not familiar with the two 750W amps they have, but I just happen to have 
> four Intech COM1000 "375W" amps (16 MRF150 in each of them). 
> Would it be possible to build a 4 square and feed each element with its own amplifier and switched phase delay?  Would this improve my 160m signal for the next Contest season? 
> What if I put it all out here: http://upload.wikimedia.org/wikipedia/en/3/39/Avila_Pier.PNG
> 
> Niko - AC6DD

I have a complete Intech COM1000 amplifier, which Intech rates at 1000W
by the way, which make the modules 250W each.  I push it to 1500W with a 
little bit of compression.  By the way, I have posted the manual at: 
http://www.n6rk.com/com1000manual.pdf.  I am not sure if you are
saying you have a complete COM1000 or just the amplifier modules.
In any event, the optimum configuration is to combine the modules
together with hybrid combiners as is done in the COM1000 and then split
the 1 signal into four parts to drive a 4 square.  In a 4 square, the
magnitudes of the currents are the same in the 4 radiators, but the
impedances vary considerably.  Therefore, the power per radiator varies.
The highest power radiator is limited to 250W or 375W (or whatever
you consider the rating of the module).  The other radiators will
take less power, and under-utilize the amplifier modules.  Four "375W"
modules will result in less than 1500W out.  Another disadvantage of
doing this is that you need 4 times as much coax to get from the shack
to the array.  In some cases the rear element can have negative 
impedance meaning that its amplifier has to absorb power.  I'm not
sure if this would work with the COM1000 modules.

The videos were interesting, although I don't know what they have to
do with amplifiers.  I notice that OM6A puts up verticals just like
I do with a falling derrick.  It works well as you can see.

Rick N6RK