[TowerTalk] Auto tuners, Baluns and open wire feeders

[Michael Tope]

On 7/17/2018 1:19 PM, Wes Stewart wrote:
> The man wants a simple, single wire antenna.  How the heck is choking 
> at the input end of a short length of open wire significantly better 
> that doing it at the feedpoint?
>
> I know you and Dean are buddies, but don't get me started about him.  
> Since he's using his software which has been shown to be in error in 
> the past, "Introducing an Improved Version of Transmission Line for 
> Windows Software"  QST, Jun 2014, p.39, I wouldn't make bank on the 
> conclusions.  Plus he continues the fallacy that a balun on the input 
> of a tuner is better than one on the output.  Shown to be wrong by 
> W7EL, W8JI, W9CF among others. ARRL's publication of such an 
> unbalanced tuner and pretending it's balanced is a disservice to the 
> community.

Wes,

If you look at the referenced article ("Don't Blow Up Your Balun"), the 
point that N6BV makes is that the differential mode loss can be greatly 
reduced when you put the balun/choke in front of the tuner instead of 
after it. The point that W9CF, et al made is that putting the 
balun/choke ahead of the tuner doesn't lessen the common-mode stress 
(nor does it improve the common mode attenuation). Thus, if the 
balun/choke is catching fire due to differential mode heating when it is 
placed after the tuner, moving it in front of the tuner may help. On the 
other hand, if it is catching fire due to common-mode stress, moving it 
won't help.

73, Mike W4EF.........

> I agree with your recommendation of fan dipoles, but that is beyond 
> the scope of the OP's desires.
>
> Wes  N7WS
>
> On 7/17/2018 11:32 AM, Jim Brown wrote:
>> On 7/17/2018 11:00 AM, Wes Stewart wrote:
>>> If your open wire is short, why bother? Replace it with low loss 
>>> coax, put a decent common-mode choke at the feedpoint and tune it.  
>>> Sometimes the effort to use open wire simply isn't worth it.
>>
>> Caution on this. See JUN 2015 - QST (PG. 30) "Don't Blow Up Your Balun"
>> by Dean Straw, N6BV
>>
>> Dean's work clearly shows why it simply is not practical to choke a 
>> non-resonant antenna. And, because receive noise is such a major 
>> issue for most of us, it's why I don't recommend antennas like this. 
>> The random wire and off-center fed wires were great ideas for 30 
>> years ago, but terrible ideas today.
>>
>> Fan dipoles are a FAR better choice.
>>
>> 73, Jim K9YC