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[TenTec] Transmatches/Tuners/Etc.

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Subject: [TenTec] Transmatches/Tuners/Etc.
From: hmmjr@erols.com (H. M. 'Puck' Motley W4PM)
Date: Mon, 22 Sep 1997 13:49:18 -0700
Maybe the Ultimate and SPC were not forerunners of the T but I never saw 
a T until after that Murch Ultimate came out.  Other manufacturers came 
out with the T, which was less costly to produce and worked as well at 
matching a wide range of impedances as the Ultimate did.  I, like you, 
had a Murch and converted it to the SPC circuit.  I felt however that the 
SPC arrangement was a bit too touchy to adjust.  

If someone has information of a T network tuner sold commercially prior 
to the Murch Ultimate it would be interesting to know what it was.  I 
don't remember any, but then sometimes I forget which exit to take off Rt 
95 when I'm driving home in the evening!

As to harmonic attenuation, that's hardly a concern these days as most 
rigs are quite adequate in this area.  A PI or series inductor L are both 
loss pass in nature and would be better than a T or an Ultimate which are 
both high pass types. The SPC is basically an Ultimate with that third 
cap relocated to give more of a band pass rather than high pass effect.

I really prefer the reversible L that Ten Tec uses.  I've never seen a 
comparison of this type of tuner with a T as to losses but I'd suspect an 
L would be better as it has one less component. I also like the fact that 
there is only one setting that will give a match with an L.  A T, an 
Ultimate and an SPC will match with any number of settings.  Some 
settings are better that others as to Q and power loss.  I can never 
remember whether I should have used the setting with the most capacitance 
or most inducatnce, etc.  With an L you just set it and go!

I'm sure you're right about the PI networks in the old tube rigs.  I just 
pulled some numbers out of the air.  My DX 20 would load power into 
everything from a light bulb, to a window screen to a short piece of wire 
lying on the floor.  It even worked quite well on an off-center fed 
dipole I had fed with 75 ohm twin lead.

Puck, W4PM

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