Re: [TowerTalk] Swinging Link Antenna Tuner Not Working

["Donald Chester" <k4kyv@hotmail.com>]

 The 1952 handbook has a real nice unit.  Swinging link is old stuff and
obsolete.  Use a fixed link and a link capacitor to tune.  I had one of 
those
with the swinging link.  used it to pivot the link out of the plug in coil 
so it
could be pulled. coil was 8" x 4" by B&W HDVL, I think.

 john w9zy



Chuck Pool <aa5wg@yahoo.com> wrote:
 Does anyone have pictures and component values for a swinging link antenna
tuner that works well. My swinging link antenna tuner will not work. I tried
feeding the open wire line in the series (current feed) and parallel 
(voltage
feed) configuration but it would not work.
Maybe my capacitor and coils are not the right values? The feed-line is 1/4
wavelength multiples. At present, I don' t want to use a series capacitor 
with
the link coil.



I use link coupling at the output tank circuit of two of my homebrew rigs.  
I use swinging link at the transmitter and fixed link at the antenna tuner, 
which is located at the base of the tower.

At the transmitter I use a series variable cap, about 1100 pf in series with 
the  link for 80 and 40.  For 160 I had to use trial and error, and ended up 
with a network of fixed and variable capacitors to form a capacitive voltage 
divider to get it to take load.  I adjust mine by swinging the  link out to 
very loose coupling, and then adjusting the variable capacitor for maximum  
loading -- just a slight peak.  That tells me the  link is in resonance.  
Then I swing the link in for the proper degree of loading.  Usually I have 
to re-dip the final when the link is swing in, but the re-adjustment should 
be very slight.

At the antenna tuner I use a series cap for 80 and 40, but on 160 I hit just 
the right number of turns on the link that no series capacitor is needed.

The xmtr and ant tuners are linked together with 50-ohm coax.

It has been my experience that getting this system to work is a matter of 
trial and error.  The number of  turns on the link can make a big 
difference.  In the past I have had to use a rotary inductor instead of 
variable capacitor to  get the link to resonate.

You can get much  better coupling by resonating the  link.  With the correct 
number of turns the link will work non-resonant, that is, directly into a 
resistive load, but I have found the whole thing to be very unpredictable.

But that's part of the fun of  ham radio.  Keep tinkering and modifying it 
until you  get it to work, then configure it permanently.

Don k4kyv

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