[TenTec] Auto tuner in Orion

[Steve Ellington]

> I vote "no" for a built in tuner (really a "trimmer"). In addition to
> the cost and space, two problems come to mind with internal tuners:
>
> 1) Limited matching range. Most internal "tuners" can match from
> (nominally) 25 to 150 ohms, not a very great range. Remember that 150
> ohms (3:1 SWR) gives the Yaecomwood fits and they NEED the trimmer for
> even a relatively minor mismatch to keep from powering down, not a
> problem with TT.
>
Yes it's a problem with TT. It just APPEARS to not be a problem. TT doesn't
use ay "fold back" protection circuit on their finals. Instead, they use a
fuse. Instead of gradually reducing power as the mismatch increases, they
allow a certain amount of collector current until the fuse blows. So the
Yaecomwoods not only provide a sophisticated protection system, they also
provide a cooling fan plus a tuner to keep the finals happy. Even a triband
beam can yield 3:1 SWRs. That "trimmer" comes in handy for this. But then of
course, FUSES are cheaper.

> 2) If you get a tuner with a wider matching range, you need larger
> components--- which don't tend to fit inside the radio. To explain
> further, Ohm's Law is the culprit. E=IR or E=IZ. The good news is, you
> want a tuner with a wide matching range, say 1000 or 2000 ohms. The bad
> news is you have Mr. Ohm causing mischief due to the high Z. For
> example, one amp of current at 1000 ohms gives 1000 volts. This high
> voltage is why you need large (wide spaced) components and why you hear
> people complain that their (so-called) 300 watt tuner arcs over with
> "only" a  100 watt transceiver.

Yes if you're going to use Mr. open wire fed dipole where the tuner might
see 2000 Mr. Ohms then certainly you need a beefy tuner but the purpose of
an internal tuner is to help the fellow who makes some attempt to provide a
50 ohm impedance to his rig but didn't quite make it. Antennas such as
loops, multiband verticals, tri band beams etc. all need a little help. The
internal tuner allows Mr. contester to band hop instantly and provide an
exact match to his finals. They do work!

Obviously, if you use an external amplifier, you'll need an external tuner
but hey, they make amplifiers with auto tuners in them to! Alpha, Icom etc.


> Keep it a real tuner and keep it separate where the radio gods intended
> it to be...

Ok...Keep the final amp seperate too. Gee, those hot transistors and high
currents can ruin the rest of the radio. Besides, doesn't TT trust us to
provide our own amplifiers? And those discusting low pass
filters....shouldn't they be left out too? We could all use external tuners
to make up for those...The "radio gods" didn't intend anything. They have
allowed free enterprise to run amok.

73 N4LQ
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