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[TowerTalk] trying 3 different T-tuner suggester programs: TLW seems to

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Subject: [TowerTalk] trying 3 different T-tuner suggester programs: TLW seems to lead an unwary user (me) astray.
From: Kevin Normoyle <>
Date: Wed, 01 Dec 2010 00:20:59 -0800
List-post: <">>
Steve G3TXQ said "If you want to get meaningful loss results with that 
simulator, be
prepared to manually change the default Q value as you change bands and
change inductance values."

Yes, if you want to just see the result for a known combination. I ran into a 
surprise assuming I understood how some things out there create a "suggested" 
result, not even considering the constant vs varying component Q issue.

I was comparing the suggested values produced by 3 T-Tuner simulations, and was 
surprised to see the difference in results. Be interested in feedback about 
other people have used/done.

1) 4nec2 which allows you to specify min network Q (lower network Q = lower 
loss). Don't need filtering, so high Q result isn't useful.

2) ARRL Antenna Book TLW (n6bv 2004)

3) The very nice t_tuner.exe from G4FGQ (free) which allows you control L and C 
ratios, and max C so you can get different results  (varying L/C ratio and 
comparing different loss/volts/current results)

4) ARRL Antenna Book ATT. I just loaded this, and see it constrains things 
differently. Am playing with it running in DOSbox.

t_tuner.exe and 4nec2 quickly let you see the effects of varying L and C for a 
given match.
4nec2 lets you specify a min network Q for the result.
t_tuner  allows you to control the L/C ratio with an artificial parameter "A" 
with small values given large C and lowest loss.

(G4FGQ also has l_tuner.exe, (L network) but I focused on T)

I got really confused looking at the TLW results. For my test case, they 
suggested a result, which was very bad for power loss?

I played with both 4nec2 and t_tuner.exe, trying to get the same predicted 
result. I get them to create the one result TLW suggests, but it's clearly not 
optimum. It's a high Q result, when I want a low Q result.  (low loss) (I'm 
using TLW high-pass Tee Network Tuner selection).

At first I thought "This seems like a bug in TLW".  I found the problem below, 
which I am calling a program design flaw..i.e. you have to have some knowledge 
to realize why it's a bad result. It's easy to believe there is only one 
possible result, and not tune things to get something good.

t_tuner is best for getting different results and comparing.
Even if I constrain t_tuner to use C of <350pf, a nice low Q result is 

The TLW suggested poor result, seems to have a Q of about 60 (reported when 
values used in the other programs)
The TLW result is a correct match. (verified elsewhere)
The suggested result in TLW doesn't seem to vary, if the unloaded component Q 
Those unloaded Qs just affect the final loss calculations.

Here's the problem:
TLW allows you to vary results by controlling one of the C's (Tee Network 
Capacitor).  You have to "know" that it needs to be increased to get a good 
result in my test case (and may need to be small to get a good result for a 
different test case..or intermediate).

If you keep that small, in my case, you get a bad result. (this goes to the 
question of the goodness/badness of different L/C match combinations)

It would be nice if they all reported final network Q like 4nec2, but seeing 
power loss is related, so okay I guess.

So what TLW is really doing is giving you a good result for what you specified, 
but doesn't give you enough info to realize you need to tweak the input you 
it, to see different possible results.

It is much nicer to specify a min-max range for C, or L, and maybe a final 
network Q, or have it find the lowest loss result.

I haven't find a program that gives a single suggested optimal result using the 
known Q of the unloaded components? Even 4nec2 seems to not use component Q's 
when reporting a  "min network q" of the result, although he modifies the info 
used later, with component Qs.

Are there some other good ways other there of getting comparative calculated 
results that I'm missing?

It seems like this could all be easily automated. Computers are fast enough now 
so that all the constraints could be described, and walk over all possibilities 
and draw the very nice info "map"  like  G3TXQ posted. (that represents "what's 
doable" with the particular set of constraints in a single real tuner).

Like an excel spreadsheet would be nice.



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