Here’s a Workbench suggestion from Wayne Kirkwood for do-it-yourselfers who need a simple ground binding post.
This particular project, a phono preamp, was sent to Wayne by a customer for test and calibration.
A threaded hex spacer makes a secure ground binding post.
The original ground connection was a slotted 6-32 screw head, poking out of the back panel and held in place by two jam nuts, one on each side of the rear panel. There was no way to tighten the screw, and the ground connection required an alligator clip.
In order to make it a binding post, Wayne reversed the screw so that the head was on the inside of the chassis, with the stud poking outward. A nut and lock washer attach it to the rear panel. The result is a 6-32-inch threaded stud poking out of the back panel. To make it a binding post, Wayne took a threaded hex 6-32 spacer and screwed it onto the stud. Wayne also recommends at least one flat “thrust” washer between the spacer and panel nut.
This solution is much neater than the original (or a wing nut) and easy to loosen or tighten by hand or using a nut driver. If there is paint on the inside of the panel, always remove it. This is so the ground connection is bare metal. A lock washer cannot be trusted to provide a good ground on a painted surface.
This trick may be obvious to some readers but it’s easy sometimes to overlook simple solutions using new combinations of standard hardware.
Tom Norman does project work, currently in Chicago; he commented about rodent infestation. He’s had success using steel wool, as we’ve discussed here, but reminds us to replace the steel wool from time to time. Steel wool becomes “rust wool” in short order, even in arid climates. Consider using copper Chore Boy-brand scrubbers or similar products made from stainless steel.
Tom once faced a situation where wires fed a NEMA electric box via conduit. Finding a nest in the box, Tom stuffed a good deal of Chore Boy scrubbers into the conduit and followed that with RectorSeal Duct Seal compound (available at Home Depot).
Tom encountered duct seal years ago when he was putting a new radio transmitter on the air. The phone company delivered their wires to the transmitter building via flexible conduit. Their cable emerged from this conduit, and the conduit was sealed against the cable by stuffing duct seal into the conduit until no more could be inserted. With that in mind, it was interesting to see it used in other places by local phone companies.
Duct seal sheds moisture and, apparently, is not appetizing to rodents. This made Tom wonder if the Chore Boy part of the solution was even needed.
Because duct seal is a putty, there are limits to the kinds of openings that can be sealed with it without providing other kinds of support. It stays pliable, even out in direct sunlight, and its viscosity changes with temperature. Its real advantage is that it can be stuffed into places you might have a hard time reaching by just forcing more of it into the area. Tom has used it to seal moderate-sized openings on vertical surfaces, and painted over it with reasonable results.
Good luck to anyone and everyone who has to deal with rodent problems at a transmitter site. There is no way to kill off all the vermin at a site, but there are ways to minimize their destruction.
Duct seal is available at Home Depot and other big box stores. A 1-pound block costs less than $25. Check out www.homedepot.com, keyword “duct seal,” to find a variety of products from Gardner Bender and Ideal. Tom normally purchases 1-pound blocks because they are manageable for small applications.
Tom also mentions that duct seal could be used in conjunction with wire mesh to manage openings of irregular size or shape, the object being to provide a surface upon which the duct seal can attach.
Steve Keating is with Mission Electronics in Las Vegas. He tell us about a project he built up for a five-tower array several years back. He needed to be in the transmitter building while a technician was in each of the doghouses. They were measuring transmission line impedances, and Steve needed to communicate with them.
A small speaker was not available but a 2-inch driver was, so he used a 4S junction box in each doghouse and a larger enclosure in the building with switches and a power amplifier to form an inexpensive intercom.
This also would work for monitoring on-air reception just about anywhere, if fed from a standard radio or tuner with line out and an amplifier mounted inside a handy box.
Nowadays, the size of things has shrunk, and Steve shares a link for a very tiny speaker.
It measures 1.1 by 1.6 inches and is manufactured by Visaton. It’s their part number K 28.40-8 micro speaker. A great choice where space is at a premium. The speaker costs about $6 and will handle 2 watts. Visiton uses a neodymium magnet that allows the speaker to fit almost anywhere; the magnet is the strongest type of permanent magnet commercially available. Because of its size, you can add audio to projects you never thought possible.
Find out more at www.parts-express.com.
Workbench — Radio World’s iconic and most popular column — relies on your good, practical ideas and those of your colleagues. Send in tips big or small; help your fellow engineers and qualify for SBE recertification credit. Email firstname.lastname@example.org. You can even (gasp) fax them to (603) 472-4944. And discover a trove of past tips by clicking on the Columns & Views tab at radioworld.com, then choosing Workbench.
John has spent almost five decades in the broadcasting industry and yet he is still learning. He handles West Coast sales for the Telos Alliance; he is SBE-certified and is a past recipient of the SBE’s Educator of the Year Award.