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Richard Clark · March 3rd 07, 10:36 PM posted to rec.radio.amateur.antenna

On 3 Mar 2007 12:04:50 -0800, wrote:

On Mar 2, 12:15 pm, Richard Clark wrote:

If you are interested in a design for yourself, and maybe a production
run of a few hundred, then look to the HF/10M/6M/2M surplus repeater
market from Motorola and RCA designs of the 70s and 80s. Dirt cheap
decks with enough elbow room to make mods.

Or, perhaps the HF Superpacker Pro.. 100+Watts..20dB or so gain.

Hmm, some 5-10 years ago me and my buddy were up to our hips in GE
MASTR IIs for one tenth the price of the HFSP. We could buy them
cheaper yet if we purchased by the pallet. Well, I suppose it's a
case of "that was then, this is now...."

So, this daydream is on one band only?

1 adjustable L, 1 adjustable C.. covers all bands. For ham
applications, you only need to have the match and phase adjust at one
frequency at a time, and over a fairly small bandwidth, so the Q of
the matching circuit can be high. Not like a generic wideband phased
array where you need to have a wideband match, and do something like
true-time-delay processing.

You might have to. I don't think an L tuner is going to have the
flexibility to look into the mutual coupling, as well as the delay, as
well as the match and be scalable to 3D. (May as well dream in
technicolor and surround sound.)

Check out, for instance, the AD9858..

Yes, things have sped up by 10 fold since I last visited this topic.

If you need to phase each array element
independently to phase steer the combined system (also to take care of
phase matching through mutual coupling), the software solution spring
immediately to the front for a solution.

Well, software for the calculations, but perhaps not for all the RF
processing. You still need to adjust Ls and Cs for the match, unless
you're willing to design a fairly unusual amplifier: ideally, it would
act like a current source with a lot of voltage compliance that can
tolerate a very reactive load.. so you're essentially synthesizing the
L and/or C with an active device.. doable, but not too hot on power
efficiency these days.

Ever hear of a gyrator?

The problem of solutions off the shelf is that they have been dumbed
down to the most generic market.

Consider your suggestion of the HFSP. Looking at the schematics
reveals the same old stale Class AB design WITHOUT neutralization.
It seems that feedback is an anathema to designers that have to pay
the piper called a commodity market. If they built a 20dB amp, and
then discarded 10dB of that gain for stability and source resistance
control - THEN you would have engineering. The 10dB cast back into
the amp loop was called "noise gain" by HW Bode; and this cured so
many ills of stability, distortion, noise, dampening, regulation...
that it its absence cheats us all of superior performance for the sake
of squeeking every dB of slop into the antenna. What would the world
be like without that filter deck following the amp? Amplifiers are
perfectly capable of delivering a low distortion HF sine wave - if you
designed it in, that is.

Early adopters are not being served there.

A solid state inductor/capacitor (AKA Gyrator) is technically a budget
buster for the chintz market; but if you design to the mission, then
there you are. To invest in digital oscillators, and then short sheet
the product with a limp re-hash Amp deck out of the 60s is not going
to ignite a new product venture.

73's
Richard Clark, KB7QHC

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