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LPFM: Like It or Not, They’re Here

While I have some concerns about technical standards and potential interference issues, most of the rhetoric strikes me as at least a little bit disingenuous, sometimes to the point that I'm looking around to see where I stashed my hip waders.

A lot of broadcasters including the National Association of Broadcasters objected when the FCC proposed a low-power FM broadcast service.

Dire predictions of unbridled interference and irresponsible operation have been around ever since the NPRM was released.

Now that LPFM is a reality, some folks are still pretty upset.

I’m an engineer. I deal with the real world of broadcasting. I leave issues like this to the folks who scurry off to their offices in a suit and tie every day.

While I have some concerns about technical standards and potential interference issues, most of the rhetoric strikes me as at least a little bit disingenuous, sometimes to the point that I’m looking around to see where I stashed my hip waders.

The Mr. Carlson clones who inhabit the front office need something to worry about and this is as good as anything else; but the fact is that, unless the new low-power licensees do some really stupid things, LPFM is here, and it’s here to stay; just deal with it.


I had an interesting experience with LPFM and came away seeing it as a real opportunity for broadcast engineering professionals that can pay off big.

I’m in Madison, Wis. Mad City is a place where all sorts of activism and enthusiasm are the order of the day. Combine that with a diverse, talented population and the raw, youthful energy of a large number of university students, and things are gonna happen.

I wasn’t too surprised to receive a call from a friend at the local community station, where I’m a consulting engineer.

He needed help. It seems that a local group he’d adopted had been granted an LPFM license and they were setting up their transmitter site. It wasn’t going well. Could I look things over?

“Interesting,” I said, raising my best Mr. Spock eyebrow. Sure, I’d be glad to drop by.

I’ve seen a lot of transmitter sites in my time. My philosophy has always been that old chestnut KISS, because the more stuff you’ve got at a site, the more there is to fail and put you off the air. Minimalist design is its own virtue.

What I saw at the newest wannabe FM in town caused me to smile with both pleasure and amusement.

Get ‘er done

Remember the old Mickey Rooney and Judy Garland movies? About halfway though, Mickey would say “Hey kids … Let’s put on a show out in the barn!” Imagination, improvisation, talent and enthusiasm always pulled it off.

That’s what I saw here. These LPFM folks have the Fire in the Belly but they don’t have a whole lot of money to throw at problems.

In a corner of a garage I saw a discarded four-foot relay rack that housed an old stereo FM exciter, an older (like 20 years’ worth) Orban decibel squasher, a nondescript personal computer and a small UPS.

I was told this isn’t the whole transmitter; they’re waiting for the FedEx man to deliver a 100 watt RF power amplifier. Other upgrades, in the antenna system, are planned.

A 5/8-wave ground plane is stuck on a section of TV mast on the garage roof, fed with RG-214. Soon it’s going to be raised to the authorized maximum height — all the way up to 36 feet HAAT.

I like it. This station takes minimalism to the extreme. There’s almost nothing here to fail. It’s simple and easy to maintain; it can be made pretty bulletproof without a lot of work or expense.

The PC provides the transmitter operator with remote control via dialup modem. Interestingly, it also provides the programming.

Around town there are a number of folks who want to be on radio. They don’t have access to a station or the knowledge and skills to set one up. What they need is just a place to put their point of view on the air.

What they do have is the means to assemble a small production studio: a couple of mics, a mixer and a PC tucked away in a basement or a corner in some student apartment.

These folks will be putting together their programs as sound files and uploading them to the transmitter site PC via the Internet. The PC’s scheduling software will retrieve and play the files back at the appropriate times.

I’m impressed.


A quick pass at the transmitter and antenna system with a TDR and Bird, some minor tweaks and setting a few DIP switches made things right. The PC pulled up a test file of Broadway show tunes and ID announcements, and a happy bunch of newbie broadcasters took to the air with an earthshaking 30 watt signal.

It’s worth our time and effort as engineering professionals to get to know these folks.

Suppose an interference problem cropped up that involved these guys? Who do you think will get the most cooperation in resolving it: a strange (and more than likely a little bit irked) chief engineer who suddenly shows up at their door? Or the friendly, helpful guy who gave them a hand getting on the air in the first place?

If you help these people get set up, or to get back on the air when they have problems, you’ve got a foot in the door. You’ll know their RF systems intimately, and you’ll be able to use that knowledge to clear up any future problems.

The LPFM operators will gain from it too; your skills and experience will make their operation more likely to conform to the both the spirit and the letter of the regulatory law.

Don’t ever sell short the value of your mentoring.

We all know that people interested in working with RF systems are getting to be few and far between these days.

How about that high school kid who looks over your shoulder every time you tweak the LPFM transmitter? Does he have the smarts and ambition needed to help you out part-time? Is he a likely candidate for the next generation of transmitter men?

Some folks will see the arrival of an LPFM to your neighborhood as the End of Civilization as We Know It; but it can be a win/win situation if you let it.

As for me, right now I’m going through my stuff for a coax surge suppressor and a scrap of copper grounding strap to add to the LPFM’s transmission line. Maybe I’ll even drag out three or four sections of used Rohn 25 that I have lying around.

Adding that to their antenna system might make it a bit more lightning-proof, and maybe even get a decent signal out to 3 or 4 miles …

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