[TowerTalk] Tuners

[Kevin Normoyle]

On 11/29/2010 8:49 AM, Steve Hunt wrote:
> That's a useful tuner simulation; but **DO** remember it assumes a
> constant Q for the inductor. Here's how a real roller inductor Q
> measures at different inductance settings on different bands:
>
> http://www.karinya.net/g3txq/temp/rollercoaster_q.png
>
> 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.
>
> 73,
> Steve G3TXQ
thanks steve. Interesting.

AH! real data? so for 160/80, Q increases for more turns (more uH). But the 
higher frequencies are more complicated.

(note the arrl article's simulated numbers used fixed Q of 200 for the 
inductance. That's typical in most simulated numbers I've seen)

In steve's picture, it's interesting how the Q decreases with larger uH for the 
higher frequencies. That's counterintuitive.
In fact it decreases for everything except 40M and 80M where it increases.

Is this because of coupling/capacitance in the coil? Is this a special behavior 
for roller inductors vs air coil (the equations for air coil were posted earlier)

It also seems that using a single Q=80 or so would be better than using Q=200, 
if you only had one choice.

Wondering about the picture. Could there be measurement error due to stray 
capacitances?

-kevin
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