Hal Kneller and I worked together at Harris and later at Nautel. Though he now is retired, he still does contract engineering.
Hal reports that at WSRQ(AM) in Sarasota, Fla., Hurricane Milton took out the glass bowl feed-through insulator connecting the output of the antenna tuning unit to the shunt feed line. A branch from a nearby tree hit the wire, cracking the feed-through insulator, as you can see in the first image.
This put the station off the air, as the tower feed was shorted to the ATU chassis through the broken insulator. Hal placed a block of wood inside the ATU to lift the feed and clear the short circuit until a replacement could be made.
Hal writes, “Yes, there are still some shunt feed AMs operating!” He said this station was one of Ron Rackley’s last projects; it feeds a cell phone tower, to which a ground system was added.
After searching eBay for a cost-effective replacement without luck, Hal contacted companies that make phasors and ATUs. Some had no stock. One quoted $600+ for a replacement. So he started looking for a block of Teflon to replace the glass bowl feed-through.
What Hal discovered was high-density polyethylene. Hal discovered that HDPE is strong as well as resistant to weather and sunlight, and it had the proper dielectric insulating properties at AM RF frequencies.
Doing an internet search, Hal came across Plasti-Block, which solved his problem.
Hal didn’t have a suitable bit to cut the 3/4-inch hole for the stainless-steel threaded rod, so the company did it for him. (Plasti-Block didn’t recommend using a wood paddle bit for this purpose.)
Using a drill bit intended for metal, Hal was able to cut the 1/4-inch holes for mounting the block to the face of the ATU, though he says a drill press would be better.
The best part is that his cost including shipping, cutting and material was about $81, and the order shipped within a few days. The second and third photos reveal the finished work.
Lacking a block that measured 8 x 8 inches, Hal got a block measuring 6 x 8 x 2 inches that covered most of the screw holes. For the others Hal just replaced the original bowl insulator screws.
Hal concludes that this material seems much stronger than the original glass and so far, through shine and rain, it has worked wonderfully and saved the station hundreds of dollars.
Drilling through counters
Frequent Workbench contributor Paul Sagi in Malaysia saw the adjustable mic track we mentioned in September from our tour of WGEM(FM/TV) in Quincy. It reminded him that he needed to drill four newsroom voice-track studio tables to mount AKG mics.
The tables had nice woodgrain veneer tops, supported by sturdy steel frames. The clearance between the mic position and the frame was low, with a variance of only 1/4-inch. The trick was to drill a small pilot hole from below, then use a hole saw from above.
This particular mic was mounted on a gooseneck, fitted with a male XLR connector. The male XLR fit into a chassis-mount female XLR, which was mounted in the hole on each table. The female connector had a release button, which Paul removed, to prevent anyone from walking away with the gooseneck and mic.
However, the small gap between the mic and the female XLR connector, caused by the removal of the release button, made the mic wobbly.
Paul filled the gap with black double-sided foam tape. One side of the tape was stuck to the mic connector, the other side of the tape was coated with talcum powder, so the gooseneck could be slid into the female XLR connector. The result was a stable connection.
Paul has also followed our discussions about blocking Windows updates, a serious problem for stations using Windows automation playout systems. Paul offers two sites that “kill” or block Windows updates:
The Windows Update Blocker does a great job of killing Windows updates, and it’s configurable in a fine-grained way by editing a text file.
Paul was unsure whether Windows Update Blocker can block the execution of an XML file. He found an XML file in Windows that was used as a timer to initiate Windows Update. He deleted the XML file instead of editing it.
Finally, Paul suggests a visit to www.grainger.com. At this writing the website’s home page features a winterization checklist of supplies.
By the way, on Dec. 12 I’ll be giving a free webinar produced by the Society of Broadcast Engineers and sponsored by SCMS, featuring tips and ideas from Workbench and beyond. Particulars can be found here.
Workbench submissions are encouraged and qualify for SBE recertification credit. Email johnpbisset@gmail.com.
