PPM and Signal Strength

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PPM and Signal Strength

Post by rogerwimmer » Thu Apr 21, 2011 9:03 am

Doctor: Have you ever eaten at the Chili's up in Longmont, CO? I saw a guy there a few months ago that looked a lot like you. I figured since you reside in a different part of the metro, maybe it actually was you. But I was too shy to interrupt your meal...if it really was you.

Anyhow, since PPM is based on Arbitron getting my station's unique code, I have been wondering if that puts certain kinds of signals at a disadvantage. Let's take my signal for instance. It's somewhat of a rim-shot. So as you're driving around, it will frequently dropout or fade somewhat. Let's say that same thing happens to our listeners who carry the PPM and the dropout happens as often as once per minute. Since I need at least 5 continuous minutes of listening to get a quarter hour (right?), will I never get credit for anyone this is happening to, since the chances of their radio NOT fading at some point in a 5-minute window are tiny? Will they ever even count towards my cume?

Thanks for whatever insight you can offer. - Anonymous


Anon: First, I have never been to Chili's in Longmont, CO, so the person you saw wasn’t me. However, if you do see me around the Denver area, please don't be shy...go ahead and interrupt me. On to your question . . .

Correction: The 5-minutes of listening in a quarter hour does not have to be continuous. A listener only needs to listen to a total of five minutes at any time during a quarter hour for a radio station to receive credit.

Now on to your signal strength question . . .

Arbitron's PPM device collects information every four seconds. If a PPM participant is listening to your radio station and the signal drops out, the PPM will not record the listening if the dropout occurs at the exact time when the PPM collects information. There is a chance that you will lose some listening time with one or more PPM participants, but since the PPM collects information 15 times each minute, the odds are in your favor that the PPM will collect information even if your signal drops out for a short period while a participant is driving around in a vehicle.

In case you are interested, here is a complete explanation of the PPM procedure in Arbitron's publication titled, A Guide to Understanding and Using PPM Data.

Let me know if you need additional information.


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Roger Wimmer is owner of Wimmer Research and senior author of Mass Media Research: An Introduction, 10th Edition.

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