Our Torrington translator site had been plagued with issues for quite some time.  Initially the issue was a poorly mounted antenna that literally destroyed the top section of the tower by twisting the tower leg in the wind until a number of the cross members broke.  That issue was resolved and the antenna mounted securely, however, the issue with poor performance remained.  I attributed it to the fact that the antenna (while now mounted securely) was still not mounted according to the manufacturer’s recommendations.  It is supposed to be stood off from the tower by about 3 feet, not face mounted directly to the tower.  Face mounting of these antennas can cause poor performance and significant distortion of the antenna pattern.

The reflected power reading on the transmitter tells the tale…This number should be 1.2 or less.  The lower the better.  2.12 is extremely bad and means that a significant amount of power being sent to the antenna is being reflected back to the transmitter.  Essentially it is being wasted as heat rather than being radiated by the antenna as it should be.

We have constructed a custom mount for the antenna that will stand it off from the tower supported by two of the tower legs rather than mounting the antenna directly to the face of the tower.

A bumper mounted capstain winch will assist in the process of hoisting the antenna and mount up the tower.  This is an extremely nice tool to have available for hanging antennas…

Reid has climbed the tower and begins the process of removing the antenna from the face of the tower…

Uh oh…We seem to have a problem.  The issues were caused not only by the mounting but by the fact that this antenna is on the wrong frequency!  This site is 89.9 yet the markings from the factory show this antenna as being tuned for 89.3.  No WONDER the performance was so poor!  In addition, it is marked as being part of a multi-bay antenna array, not a single bay antenna.  This can cause problems since the tuning on individual antenna bays is substantially different when they are part of a multi-bay array…

A better view of the antenna bay (with radome removed)…

Fortunately, these antennas CAN be re-tuned within a limited range.  This strap is part of the tuning mechanism.  Note the pair of marks where the strap WAS located.  Quite a far cry from where things are after being re-tuned for the proper frequency…

These antennas also have a sort of “fine match” on the end of each element to adjust the length for best tuning.  Normally brass spacers are used to keep the end caps at the right length but other hardware will have to do in this case…A small nut puts pressure against the threads in the end cap to keep things in place. (Yes, Mark…I KNOW that should probably be a non-ferrous brass nut but we had to use what we had on hand…)

We were able to mount the antenna far enough off the ground using the mounting hardware we had fabricated to tune and test the antenna before re-mounting it on the tower.  Being too close to the ground or any large metallic objects will affect the tuning so we attempted to get it out in free space as far away from other objects as possible.  It seemed to work just fine.  Unfortunately I did not anticipate this issue and did not have the proper test equipment with me so I had to tune by using the transmitter’s reflected power indication, making small adjustments and watching for the reading to get better or worse.  It worked!

Ben and Reid reattach the radome to the antenna…The tower section on the ground is actually the one from this site that had failed due to previous improper antenna installation.  We used it as somewhat of a measurement guide when designing new mounting hardware.

The antenna and new mounting hardware going up the tower while Reid watches and waits…

Ben operates the “tag” line to keep a handle on the antenna as it ascends the tower.  I am operating the winch line to actually pull it up the tower.

Done!  The antenna is now mounted properly to the tower.

The improvement was significant.  I was able to get the number as low as 1.15 on the ground but 1.28 is not terrible, particularly for just “field tuning” the system without the proper test equipment.