[TowerTalk] amplifiers for phased arrays

[Tom Rauch]

> Feedback and real time adjustment is a given...  Even in
an all passive
> array, one needs this.
>
> I'm just looking for "gain blocks" that are available
essentially off the
> shelf and won't require extensive
redesign/modification/extra parts. Sure..
> one could gut a MFJ and move the filters outboard with
relays, for instance,
> or, even, hook a stepper motor up to the band select knob.
There's more
> than one tetrode based amp that basically does just this,
with motorized
> tank components.

You'd better look close at IMD. Solid state amps are
generally ratty. The ALS500 is suitable only for use in
mobile installations where the signal level is modest. Most
of the other 12V amps are worse yet!

The ALS600, having real 50V FET's designed for linear
applications is OK, but not exceptionally clean. It compares
very favorably against tetrode amateur amps (better than
many). Of course tetrodes are not nearly as clean as GG
triode amps. Then you have the problem of mutual coupling
between elements back-feeding each amplifier. How will you
handle that?

I can't imagine why anyone would want to use amplifiers to
drive each element in an HF amateur array. It is almost
certainly an inefficient wasteful system, and for all the
aggravation it wouldn't work on receive (where most of the
advantage of having directivity occurs) without even
substantially more hardware.

My curiosity is piqued. Why would anyone want to do
something like this?

73 Tom