The things one finds when you open up a defective coax line…

I thought I’d post a few photos of a repair done some time ago to show this comedy of errors, found when the VSWR on a particular FM broadcast antenna system went high:


This shows an air leak detected at a splice in the 3″ line while up a tower several hundred feet.  Soap bubbles to the rescue!  If air can get out, water can get in.


Here we see the leaking connector splice opened up to reveal not only a burned Teflon insulator, but a shop rag and copper chips left when the connector was field-installed!  I always wondered about the dielectric strength of a shop rag…


Further up the tower at the antenna input proper, we see two views of a common mistake when assembling EIA coax, a split bullet.

Note how the burning is concentrated on the right side of the downward facing bullet, left loose by the lack of tension caused by the one finger being outside the inner conductor.


Any time this type of work is done, it always pays to hire the most professional climbing team for the job.

A lot of this type work is done at night and under time constraints, during the least revenue value time of the broadcast day.

Care and expertise must be exercised in order to prevent the illustrated types of failures.



Atop South Mountain in Phoenix, Signals worked on completing the install of a new Nautel NV40 FM transmitter for CBS Radio, at KZON-Fm 101.5.  It is an HD facility.  This upgrade replaced an aging Continental 816R4.


Shown are some of the steps involved, to include the 400-Amp disconnect with 4/0 welding cable (to ease bending), and conduit work into the transmitter:




A shot of the link between the site UPS units and the transmitter input for the controller and exciter power:


Also shown is a rear penetration into a floor duct for interface cabling:


A closeup of the transmitter main ground, with a hand nut, so checking it periodically can be accomplished without needing a wrench. (This is meant to be both fun and functional):


The crew from CBS is Chris, Eric Schecter (DE for CBS Phoenix), and Paul.  All are exceptional broadcast engineers, and a pleasure to work with:


I’ll be continuing this post further down the road, as we will be upgrading all the RF switching at this site.