Topband: Antenna Tuners

[Gary Smith]

> I have e-mailed Palstar but, to date, they have not responded. I would 
> love it if someone would come up with a high power, fully weatherized, 
> remote tuner.

I was in a dilemma back in Illinois, I had a Heights 100' aluminium 
fold over tower but insufficient land to put down sufficient radials 
in all but one direction. I had though, excellent results in my condo 
before that, using shortened loop antennas made of copper pipe, 
mounted in an octagon shape hanging  against a wall upstairs. That 
got me to thinking...

I remember reading they were supposed to be 95% transmit-wise, as 
effective as a dipole at the same height. The Q was so high on 80M 
that there was only around 3-4 KHz available at the resonant 
frequency. 

At first, in the condo, I used a vac variable across the feed point 
and adjusted it with the Rx in the room. It was like using a crystal 
radio in that once set, I was essentially rock bound to that 
frequency; at that resonant frequency I could adjust to 1:1 but past 
2 KHz either side and the SWR would be too high. At least I got on 
the air and could call CQ and I made more than a few ATNO that way.

When I moved to the house and had that Heights fold over tower and 
couldn't put down radials for 80, much less 160, I remembered my fix 
at the Condo. This time I built short center fed delta loops for 80 
and 160, mounted them apex up at the top of the tower, just below the 
rotor. It looked somewhat like a K9AY mounted at the top with one 
delta 90 degrees from the other longer delta.

I mounted Vac Variables inside plastic sealed mail boxes mounted to 
the tower at the feed-point, connected them to servos and had the 
servo counterpart in the shack in the basement in a cabinet with 
Groth counters attached to each. The Q was less on these antennas 
because the loops were larger than they were respectively in the 
Condo. Still a high Q but I could get 5-10 KHz of ideal SWR before 
needing to re-adjust the servo (Enough I could effectively run split 
using the Corsair's external VFO). 

With the sensitivity to resistance you get with the servo, it was 
instantly obvious when you were at either end of travel with the Vac 
variable so no chance of damaging the bellow, I could run my legal 
limit amp with zero problems, ever and regardless of where I was on 
the band, I had a 1:1 SWR at the feed-point. 

After a few days of becoming accustomed to the system, it took 
seconds to get me perfectly on frequency. All you needed to do was 
listen and adjust. When you were away from resonance, the radio was 
totally silent except for radio hiss, when you heard the band come 
alive, you were close to resonance, almost ready and could operate. 
Look at the SWR and adjust the final couple degrees of turn and you 
were at 1:1.

It worked perfectly, every time, never failed, always gave me 1:1 at 
the feed-point and considering I had no way to get a really ideal 
antenna up for 80 & 160, this gave me years of excellent operation on 
those bands.

73,

Gary
KA1J