[Elecraft] Using the Antenna Tuner in the XPA100

[Mister Mike]

Folks……

I found this posting by Wilson Lamb in response to my inquiry about using an automatic antenna tuner with a random-length wire antenna to be highly offensive in tone.  In my opinion it is rude, insulting and objectionable.  

I am “old school” and still run and maintain a full Collins S-Line station.  I understand how my Collins 180S-1 wire tuner works.  I have used one for about fifty years.  For those of you who do not know the 180S-1 it is a manual version of the military 180L-3 that was designed specifically for tuning random length wire antennas in aircraft.  

The 180S-1 consists of an L network which is formed by a variable air-capacitor on the input, and a variable roller inductor as the series coil.  It is then possible to expand this network (by means of a jumper) with a vacuum capacitor on the output of the "PI", in cases where the tuning solution would call for this.  The vacuum variable capacitor can be either shunted on the output, or placed in series with the inductor. This configuration allows for virtually every kind of antenna to be tuned.  

The “automatic” antenna tuner is a completely new concept for me.  They appear to be designed to tune unbalanced coaxial feedlines and not an end-fed wire.   I have one in my K3 but prefer to use the 180S-1 or my B&W VS1500A which is a “transmatch” based on the design by Doug DeMaw, W1CER/W1FB SK in the 1960s.

Thanks to a couple of useful replies from list members I was able to confirm my idea of feeding the wire through a balun and/or an unun.  But knowing how unforgiving solid state final can be when they see a bad mismatch I wanted to exercise some caution before possibly damaging my transmitter.   I am more familiar with 6146W finals than whatever transistors are used in the KXA100 which I am sure are expensive to replace.

Take a good look at what Wilson Lamb wrote and tell me if you agree of my assessment of his answer.  It didn’t offer anything constructive at all, just a cranky rant drom someone who may have forgotten the concept of what amateur radio is all about.  My response to him is that if you can’t offer anything constructive then don’t offer anything at all.  

Happy Fourth!

Michael Crestohl, W1RC
Marblehead Mass.

Wilson Lamb via Elecraft wrote on 7/1/2022 11:03 AM:
> This is so far off the wall it can't be answered...there is no answer.
> Please read my rant on Ham Qualifications.
> Then ask yourself why the tuner might have a two wire output connection.
> Then read about what impedance is.
> Then read about what the impedance at the end of your wire might be.
> The answer is that it can be too high for your tuner or too low and anywhere in between.
> Then read about matching networks and what they do.
> Then read about how the end fed wire needs to be used with a ground of some kind.
> You'll soon see, if you do the above, that what you propose is a recipe for getting an RF burn, confusing your internet modem and phone system, or even damaging your radio or tuner.
> 
> The real best answer is to get a manual tuner, connect the antenna AND A GROUND (rod) and learn to use it.
> Yes, the auto tuner "can" work, given a ground, but it pretty surely won't work on all bands.
> The end of the antenna and the tuner "should" be well up above your radio, like at the top of a window, and connected back to your station with coax.
> 
> Someone here may have time to explain all of the above to you, but it's a tall order.
> WL