[TowerTalk] Auto antenna tuner

Jim Lux jimlux at earthlink.net
Sun Mar 28 14:54:12 EST 2004

----- Original Message -----
From: "Noel" <y.yaesurigs at verizon.net>
To: "'Jim Lux'" <jimlux at earthlink.net>; <towertalk at contesting.com>
Sent: Sunday, March 28, 2004 7:41 AM
Subject: RE: [TowerTalk] Auto antenna tuner

> Jim,
> You're right about the lack of high power capable auto tuners.  I don't
> quite understand why.  I'm no engineer but it would seem a natural
> evolution to incorporate auto-tune features into some of the very
> capable roller inductor style tuners on the market. I can find several
> auto tuners rated under 200 watts that have the features I like but only
> a few that can handle up to 1K watts or so.  And then the features drop
> off sharply. i.e, no dummy load, no balun, no antenna switch, etc.

I can hazard a guess as to why.  It's mostly marketing..
At that power level, you'll have a fair amount of money into your whole
system.  Most hams probably don't go out and buy the whole QRO setup all at
one shot, but accumulate it over a period of years.  There are several
"sweet spots" for selling price for things to go in your system, and a
series of  few hundred dollars purchases is easier to implement than a
one-fell-swoop investment of a kilobuck.

There's also the thing that the total market for QRO equipment (in the ham,
non-commercial) market is smaller, so it's less likely that any arbitrary
all-in-one configuration will meet everyone's needs.

This pushes towards a system that is composed of individual components or
functions.. A high power tuner here, some coax switches, a dummy load or
two, etc.  For that matter, a high quality 2kW dummy load is no cheap item
either.  I suspect most hams wind up accumulating such things surplus or
hamfest, rather than buying new.  It's also kind of hard to figure exactly
where you want that dummy load in a ATU setup anyway.  On the output of the
amp for testing and tune up?  Doesn't do much good on the output of the
tuner, since the whole purpose of the tuner is to match a non-50 ohm load.

For what it's worth, there ARE automatically motorized LC tuners out there
as well. They're just not cheap, and the tuning speed probably isn't as good
as a relay based system.

For a commercial/military type application, where rapid frequency changes
are needed (ALE links, for instance), you need fast speed, and nothing will
beat a "power DAC" type tuner with 1:2:4:8 type fixed components and relays
and a smart controller that has presets. They can literally tune in a few
milliseconds (whatever the contact settling time on the relays is).

I think, also, that as far as losses go, a switched inductor is probably
lower loss than a roller inductor.

Jim, W6RMK

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