[Elecraft] OT: manual & automatic tuners

[tlogan7@cox.net]

Ron - That;s a great lesson in history and I for one am going to file it
away in my notes. Sure makes one appreciate the modern coveniences! Thanks
again for such great input. 73/Tim NZ7C
----- Original Message -----
From: "Ron D'Eau Claire" <rondec@easystreet.com>
To: <elecraft@mailman.qth.net>
Sent: Saturday, January 11, 2003 3:21 PM
Subject: RE: [Elecraft] OT: manual & automatic tuners


> The first fully-automatic ATU for  HF that I "met" was a Collins unit
> built for aircraft use on B-50 bombers in the 1950's. (The B-50 was a
> B-39 "Superfortress" on steroids with bigger engines, propellers and a
> taller vertical fin. It was among last of the piston-engine bombers used
> by the US Air Force).
>
> The ATU was part of a Collins HF radio SSB/CW system that was truly
> "state of the art" for the Korean War era.
>
> That was decades before cheap logic systems were available to manage the
> tuning process. Simple sensing circuits drove electric motors that wound
> capacitors and inductors back and forth to find the lowest SWR on the
> link to the transmitter. They were slow and 'clunky' with a great deal
> of sensitive machinery to go wrong.
>
> It's important to remember that the "computer" of the future, in the
> vision of folks back then, was a mechanical man who would bring you a
> fresh-brewed cup of coffee while you operated late at night. Building
> any truly "automatic" machinery was a major undertaking and expensive.
> Having a fully automatic ATU to switch between Ham bands made about as
> much sense as buying a Ferrari to drive to the grocery store, and darn
> near as expensive. Tuning up the "finals" in a Ham rig was a natural
> part of "firing up" to operate on any frequency.
>
> There were a few manually-tuned ATU's around then. They showed up mostly
> to let ops using the new single-ended pi-net outputs of their post WWII
> rigs feed their balanced open wire feedlines. Also, TVI was forcing many
> hams to use a low-pass filter in the feed line. The low pass filter is a
> fixed tuned affair that requires a low SWR on the line. Often an ATU was
> the only way to provide that. Even so, the ATUs were expensive compared
> to the typical transmitter or receiver. Most hams simply hooked their
> antenna to the rig and operated very happily, "tuning" their finals to
> match the antenna.
>
> Then came "no tune" rigs (like the K2 and all the factory-boxes the
> preceded it). No tuning controls meant the operator didn't have to do
> anything but spin the VFO to QSY, and it made for much smaller rigs.
> (Think how big a K2 would be if it had large variable caps and
> bandswitches with front-panel knobs on the inductors to cover all the
> bands.)
>
> The problem with our modern rigs was that they are  NOT "no-tune", they
> are "FIXED-TUNED". They are fixed-tuned to deliver power to a 50 ohm
> non-reactive load or they won't work. Few popular antenna designs could
> provide that over even one Ham band, much less several bands.
>
> Some Hams settled on operating only on a portion of a band or, at most,
> on a couple of bands. Others bought fairly expensive antennas that had
> all sorts of complex matching networks to present the required load to
> the rig across several bands.
>
> Then came the WARC bands, which made the antenna design problem even
> worse. That brought back the ATU, which is really just a replacement of
> the "tuned" output network in the rigs of the 50's and 60's. And
> following that came the modern "automatic" tuner. Now they were a bit
> cheaper (I bet those early Collins units cost as much as several typical
> Ham stations back in the 50's).
>
> Who said that things don't go around in circles? As Julian pointed out,
> it was somewhere 1980 that automatic ATUs started becoming popular in
> Ham stations. Now we're back to "tuning up" again, only instead of
> swinging a knob and watching a meter, we push a button and listen to the
> clicks.
>
> The modern ATU is a wonder with a built-in "computer" that tunes it up
> in seconds and even remembers the settings for each band.
>
> But it still can't make a decent cup of coffee.
>
>
> Ron AC7AC
> K2 # 1289
>
>
> I don't know when they were first introduced but I've seen automatic
> tuners that look to date from the 40's or 50's, maybe even
> earlier...they look to be some type of commercial, military, or maritime
> gear.t be done at operating power but again, if the settings are
> recorded, you can usually just return to those settings and operate.
>
> Lou W7DZN
>
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