[TenTec] Model 238C Tuner Questions

Richards jruing at ameritech.net
Tue Oct 16 07:19:42 EDT 2012

Greetings TenTec Tuner Mavens --

I have a new Model 238C tuner.   It is a different design from my two 
Palstar tuners, one a manual tuner, the other an auto tuner.

I have a couple of questions which relate to my getting used to this 
different sort of tuner...

1)  It is normal and expected that it has a VERY narrow effective tuning 
range?  It is extremely fussy, and while I understand an L type tuner 
has only one match point,  I am finding it very difficult to find that 
point, as it is a very narrow, sharply defined range.

2)  I am trying to match an OCF dipole - which presents SWR of around 
4:1 on a couple of bands, and as low as 1.2:1 on others.  It seems to 
work best on the first Low-Z (1) and I only need to turn the inductor 
two rotations, and the capacitor works best below the zero (0) mark. 
That is where the capacitor has gone entirely around and is over lapping 
  on the far side of the range.   Sound OK?

3)  Does anybody have a simple description of the procedure one should 
use to quickly find the sweet spot?  Here is what I am doing, but not 
sure if anyone has a better approach:

	I turn the Capacitor to Zero (0), and the Inductor
	all the way to its Zero (0) mark, to start  with.

	Then I transmit with the handy "Tune" button
	on my Omni VII, which puts out a bit less than
	20 watts tone.

	I turn the Inductor knob clockwise until I see a
	substantial dip in reflected power.   Then I
	rotate the Capacitor knob clockwise until
	reflected power dips sharply to a low point.

	At this point it is typically only as good as
	1.5:1 SWR - so I again slowly rotate the
	Inductor clockwise until reflected power dips
	again, and, finally, rotate the capacitor clockwise
	until a really low  match of  1.1:1 SWR or
	1.1:1  SWR is achieved.    	

	But this is a really sharp, narrow point on the
	capacitor dial - very slight movement of the
	capacitor dial shifts SWR dramatically.

	Does this sound normal?

Note:   I tried it on a couple of different Low-Z and High-Z settings, 
and it seems to work best on the first (1st)  Low-Z setting.

3)  I wonder if there is a simple way to use my RigExperts AA-230 
antenna analyzer to determine if the antenna has high or low impedance 
so it would be easier to determine, in advance, which High-z or Low-z 
setting to start out with or to confirm my selection and best guess as 
to which works best ?


(I hoping this makes sense... it seems hard to put all this into words, 
after all...)

-------------------- K8JHR  -----------------------------

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