[TowerTalk] finest tuners and switches

[Tom Rauch]

Hi Tom, 

> The finest antenna tuners and switches made today....Bar NONE!
> http://www.tomstubes.com

Inside photos would be nice. I don't know why every manufacturer 
doesn't do that. Is this tuner built with new parts, surplus parts, or 
used parts? It looks sorta surplus, with the big knife switch and all. 

Tuners are one of the toughest things to build, that's probably why 
there isn't really any ideal tuner. It just depends on what the end 
user is doing with the tuner.

For example, with an L network using the component values listed 
for that tuner the lowest pure resistance matched on 160 meters is 
either 37.7 or 25 ohms, depending on how the input transformer 
circuit is configured. A conventional "T"  has a much wider 
matching range, especially with low impedances. That's why they 
are so popular and rare. Unfortunately most T's use small value 
capacitors and poor inductors.  

As another example, moving the balun to the input does not 
improve balance. That is a popular but incorrect myth. I see some 
of our handbooks even repeat that myth.

In order to improve balance by moving the balun, the tuner must 
have at least two ganged capacitors and two ganged inductors that 
are grounded to the chassis at the middle. Even then, it only 
improves balance when the load is absolutely perfect. It is actually 
better to use a choke balun on the output in almost every other 
case, as amazing as that might seem!


73, Tom W8JI
W8JI@contesting.com 


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