When you buy air time, get this one thing right

Most business are sold advertising packages based only on audience size and total # number of hits, called gross impressions. This is a mistake. It can make you stop your radio or TV and comment "I tried radio (or TV) and it didn't work."

That's because no one person in your audience - made up of the total of every station you're on - hears your commercial more than a couple of times a month, if that. You can hit tens of thousands of people in this way and get almost no response.

You must buy what's called frequency -- it's the number of times any given person hears your commercial within a 7-day period. It's derived using a formula that stations who subscribe to ratings services such as Arbitron or Nielsen are provided with.

Get with your rep and tell her or him you want a frequency of 3 or 4 measured only across a single week in your schedule. If you're running a sale, run it no longer than one week, with a frequency of 5 or 6. There's more, and it's crucial:

Radio divides its day into what are called dayparts. They are 6-10 AM, 10-3 PM, and 3-7 PM. Anything between 7 PM and 6 AM has a fraction of the audience at a fraction of the price, so advertise there only if you don't have the budget to do at least one daypart the right way.

If you're dealing with a station or group of stations who don't subscribe to a ratings service that allows them to determine the necessary numbers for good frequency, there's a way to do it that will be a reasonable guarantee.

Start with 6-10 AM. Get a quote on the price of 2 or 3 commercials within that time five days a week, no fewer, for a total of 10-15 commercials per week in that daypart. Subtract the cost from your radio budget. If you have enough left over to put 2-3 commercials into the next daypart, 10-3 PM, five days a week, do it. You can skip every other week if you must.

Again, re sales, run a sale for just one week with a frequency of 5 or 6 within any given daypart, buying as many dayparts as you can afford. Never skimp during any daypart.

If a station rep wants to sell you a huge number of commercials spread out over all the stations in his or her station group, which is called a broad rotator, don't. The rates are cheap, but you'll get no frequency, it likely won't work, and you'll be soured on radio.

For television, never buy the TV equivalent: a lot of commercials over a lot of programs, cheap. Again, no one person will see your message enough times for your commercial to work. These packages are also broad rotators. Never buy one. They do not work. Buy programs only, under these conditions: the program must be on five days a week, and you must buy at least two commercials in every program, for a total of ten commercials per week per program. Again, it's to guarantee frequency, without which there's no motivation, no retention, no top-of-mind awareness. If your rep is told by the station to sell rotators, he or she will point out that the cost-per-commercial doing it by program is higher than with a rotator. But what you want is effectiveness, not bargains that are no bargain at all.

But say you do buy incorrectly, and your friends tell you they heard your ad or saw it on TV. That's proof that "it's working," right? It's not. They're telling you because they know you. That's what drew their attention. They're not going into every store that advertises, telling them they heard or saw their ad. You and I certainly do not do that. If we see someone we know in an ad, we'll tell him. But seeing someone you know on television or hearing their ad on radio has nothing to do with whether the appeal is a good one, whether any one person is hearing it enough to take action, or whether the ad is written in such a way as to motivate customers to come see you.

Finally, radio is referred to as "advertising's champion long-distance runner." It works best over the long haul. It is the least expensive way to reach the greatest number of people the greatest number of times with the necessary frequency to be effective. The secret is to look at your radio advertising the same as you look at the light bill. You don't go around in the dark, and you don't advertise in fits and starts. Both are long-term.