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Change Your Filters to Avoid Cooling Problems

And where can you find a reasonably priced Yagi antenna?

air filter
Fig. 1: Don’t forget air handler filters — and make a notation when the filter was changed.

How does that saying go — “Out of sight, out of mind!” Don’t let summer go by without changing out your air conditioning filters. Not only do clogged filters cause your cooling system to work harder, but the dirty filters can actually cause your system to fail prematurely.

As we have less time to visit sites (and to crawl up on the roof or into the studio ceiling), filter change-outs are easy to forget. If it’s been awhile, take a peek.

If you’re not using the more expensive high-density filters, consider switching to those. They will keep systems cleaner, and if you order them in bulk from companies like Grainger or others online, prices can be very reasonable.

If you’re fortunate enough to have snagged a summer engineering/remote intern, task them with logging the number and size of all the filters you use. Then, as the filters are changed, make sure they are dated, as seen in Fig. 1.

It’s also important that the filters are inserted properly — the arrow on the side of the filter points to the direction of air flow — make sure filters aren’t installed backwards!

[Maintaining Liquid-cooled Transmitters]

With the humidity being sucked out of the air during the summer, now is a good time to check the condensate drains. Big box stores and HVAC suppliers sell condensate drain brushes that can be used to keep the drain lines clear, as well as tablets that can be placed in the drain pan to prevent algae formation.

If you’ve ever cleared an algae plug, you know how strong the fibers forming the plug can be. A little preventive maintenance will avoid flooding problems later. Preventing a flood is crucial if your air handler is mounted directly above a studio or transmitter.

Fig. 2: Filtrete has these air fresheners that clip on the filters — freshen up your studios!

And while we’re on the subject of studio air, let’s face it — studio air can get especially rancid, so you might want to try Filtrete’s new filter air fresheners. Seen in Fig. 2, these fresheners clip onto the air filter to provide a more pleasant scent for these rooms.

Got other air conditioning system tips or suggestions? Send ideas for inclusion in a future column to [email protected].


Wayne Eckert is with the Florida Rural Communications Cooperative and is no stranger to Workbench.

Over the years, Wayne has read a number of questions and laments by broadcast engineers trying to locate a source for FM band receive-only Yagis, commonly used to feed off-air transmitter monitor receivers. Once upon a time, this product was marketed by most TV antenna manufacturers, but with the growing popularity of satellite, cable and streaming TV services, many of these companies have gone out of business.

Wayne discovered that the few broadband Yagis on the market are either aimed at audiophiles, which equates to over-the-top pricing, or CATV Yagis, which also have a price tag that will likely make your GM hit the roof.

But all is not lost! Wayne found a product made by Stellar Labs and sold by Newark.

Wayne lives in the middle of nowhere in southwest Florida; he needed an FM Yagi, since the transmitter site he wanted to monitor was about 55 miles away. The Stellar Labs product did a very good job for a very fair price (single quantities available for $32.54), according to Wayne.

The antenna is a four-element Yagi, consisting of one driven element, one reflecting and two directing elements. The result is tremendous directivity and forward gain.

Wayne adds that another really nice feature that engineers will like about this antenna is that a mast mount is included, and the mount can be tilted either up or down to match the elevation between the transmitter and the studio. On, enter part number 30-2460 to obtain more information.


Frank Hertel, consultant with Newman-Kees RF Measurements, has discovered yet another inexpensive method of labeling cables.

Manufactured by Mr-Label, and available from Amazon, these letter-sized sheets of self-adhesive cable labels are waterproof and tear-resistant and come in five assorted colors. Laser-printable or hand-printed with a Sharpie, a packet of 10 sheets (300 labels) is under $10.

On the Amazon, search for “Mr-Label US letter sheet self-adhesive cable label.”

Contribute to Workbench. You’ll help fellow engineers and qualify for SBE recertification credit. Send Workbench tips and high-resolution photos to [email protected].

Author John Bisset handles western U.S. radio sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.