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Understand the Rules on RFI

It's probably one of the most disturbing phone calls you'll receive as a chief engineer. A neighbor calls and explains he is picking up your AM or FM station on their new television, and the new TV is encased in this nice big piece of furniture they bought from Sears.

It’s probably one of the most disturbing phone calls you’ll receive as a chief engineer. A neighbor calls and explains he is picking up your AM or FM station on their new television, and the new TV is encased in this nice big piece of furniture they bought from Sears.

The neighbor picks up a power-line filter, thinking the RFI is coming in through the power cord. While at the retailer, the sales guy says it’s the responsibility of the radio station to “do whatever it is they do to mask this interference,” and by the way, they don’t have power-line filters.

On to Radio Shack, where the clerk repeats the radio station responsibility line. The neighbor now calls Sony, and after trying some of the hints in the instruction manual, the Sony technician also agrees it’s the station’s problem.

What to do?

Contract and special projects engineer Mike McCarthy of McCarthy Radio near Chicago suggests showing the neighbor a copy of the blanketing rule. This rule shows, in black and white, what the station’s responsibilities are for curing RFI. Explain the rule and do the math in the rule to show him how blanketing works.

Mike also reminds us to point out the one-year rule, high-gain antenna provision and other preclusions.

Then write a letter to the Sears and Radio Shack on station letterhead, signed by the GM, with a photocopy of the rule. Tell them they are misleading the public by acting as practitioners of law by suggesting that the station is at fault without knowing the rules or the whole picture. If you are uncertain, ask the manager to check with the station’s communications legal counsel.

Mike wishes there were a form of legal recourse for suing those who spread incorrect information like this. The worst part is this falls in the engineer’s lap. Don’t ignore it; many a station has been inspected when a consumer’s complaint fell on deaf ears, and they figured out whom to contact at the FCC.

In one case, a complainant contacted his congressman, who just happened to sit on the subcommittee that funds the FCC. You can bet the station got visited. Have to keep those constituents happy.

When I was chiefing stations, I kept a form at the front desk for the receptionist to complete for any interference call. It included a section for the complaint, and a section that my assistant or I completed as to what action we took. We kept the completed forms in a file, just in case.

. . .

Here’s an item to add to your resource list.

Howard Kahan is vice president of HLK and Associates in Ohio at (800) 222-3855. In addition to providing a line of Bud Industries racks and enclosures, Howard specializes in locating obsolete and hard-to-find electronic parts.

You’ll find the Web page at

. . .

Over a decade ago, many stations went through the arduous and costly task of removing PCB capacitors from transmitters and power supplies.

Not everyone participated, and some engineers find PCB-laden transmitters still in use. A chief recently inquired of the radio-tech listserv of how to handle the PCB problem.

Perhaps one of the best replies came from Frank Giardina. He suggested calling your local power company. General Electric Industrial Apparatus Service can handle disposal, but many power companies have to deal with this problem, and should have some suggestions.

. . .

Everyone likes to save money, and Hal Kneller, chief engineer for WZZS(FM), WZTK(AM) and WZSP(FM) in Zolfo Springs, Fla., offers a tip for engineers maintaining the Harris Gates or SX series of transmitters.

You may have found that the MOSFETs used in these rigs are getting expensive to replace. The IRF-350 will work just fine, and can be purchased from for about $10 each.

Gary Liebisch, AM applications engineer for Harris, agrees. He has used them himself when he was a chief. Don’t forget to tell your manager that you’re saving her some money.

. . .

Aaron Winski is 25 and the director of engineering for an 18-station group with stations mostly in Illinois. With that many stations, time is always of the essence, so shortcuts and gadgets play a major role in Aaron’s workday.

After years of profiting from tips in Workbench, Aaron shares one of his own. Fig. 3 shows a set of test leads made using male and female XLR and 1/4-inch tip-ring-sleeve (TRS) connectors. The leads were soldered from a package of Radio Shack alligator test clips. They help when you are testing, injecting tones or connecting a scope, and belong in everyone’s tool bag.

In fact, now that remote season is underway, put a set in the remote kit. Aaron stores the adapters in a small canvas zipper case from the local electronic supply house.

You can take Aaron’s idea a step further by making up mating connector cables for your Potomac generator and analyzer and your favorite equipment. Back in the days of “all cart machines all the time,” DB or cinch plugs connected to the connectors used on the Potomac equipment made adjustments and alignments a quick process. And you didn’t need to remove the equipment from the control room. Just make sure you make the cables lonnggggg.

Making up test cables like this is a perfect intern’s job. He or she will learn how to solder; you get the cables manufactured. So what if they have to solder the connections a hundred times until they get it right? Everyone benefits.

What, no intern? Check your phone book for electronics schools, community colleges or trade schools. Many of these programs have work-study arrangements that can be a real benefit to you.

Submissions for this column are encouraged, and qualify for SBE recertification credit. Fax your submission to (703) 323-8044, or send e-mail to [email protected].