Some years back, I had a production team shooting a TV drama only a few blocks from my home.  When I discovered the sound mixer was an existing client, I invited myself onto the set where he was delighted to show me his latest purchase.  The most fantastic wireless mike aerial ever invented.

To my great dismay, this turned out to be a Log Periodic Dipole Array (LPDA) a.k.a. shark fin, or bat wing, aerial. He explained to me how it doubled the range of his Lectrosonics 195D ‘quad box’ (I hasten to add it was not a Lectrosonics aerial).

After four decades in RF technology, I felt humiliated when he disclosed his discovery; embarrassed by my lack of awareness. 

If I do say so myself, mine was an academy award-winning performance. I was not about to inform my client it was all in his head.  There is no reward for pricking fantasy bubbles and he wouldn’t have believed me anyway.

As soon as I arrived home, I looked up the aerial on the manufacturer’s web site.  It clearly stated ‘unity gain’.  My client had deluded himself into thinking his latest toy had performance that not even the manufacturer laid claim to.  BTW... Have you noticed that European manufacturers are conservative in their claims?  It's a cultural thing... something to do with honesty and integrity I believe.  

This is not the first time I have been found pathetically lacking in my knowledge of devices that have been around for decades.  I am constantly being updated by clients who make these revolutionary discoveries on a regular basis. 

Reputedly, the circus proprietor P.T. Barnum once said:  

"There’s a Sucker Born Every Minute."

Most western countries have consumer protection laws to limit the claims of snake oil salesmen.  You only have to watch late night television to quickly reach the conclusion those laws don’t apply after midnight.

In the LPDA case, the manufacturer had honestly stated the aerial performance.  It was the consumer who was making the ludicrous claim.

The above story reminds me of an old fable called Stone Soup. 

Those of us who work in science or technology tend to be skeptical creatures.  We rely upon data and accurate feedback when forming conclusions, especially those that defy the laws of logic or physics.

In evaluating an aerial, we would compare the device with a known reference device, typically the simple dipole.  It is absolutely essential in our evaluation that we make every other factor under test identical so that all variables are eliminated.

Had my client done so, he would have found little improvement in his latest acquisition.  When he added the two shark fins, he had mounted them on poles above his sound trolley.  His original aerials were the humble Lectrosonics whips that came with his UCR195D.  These were mounted on the back of his Quad Box which was on a trolley shelf. Apart from the fact his LPDAs were now mounted much higher, they were unobstructed by the metal frame and shelves as well as the Quad Box itself.  Had he simply relocated his original whip aerials to the same position he created for his LPDAs, he would have greatly improved the range. 

How do you explain to a client that his assumptions are ill-founded and that his financial investment contributed to an insignificant (if any) improvement?

The answer is simple.  You don’t!

Shortly after WW2, an ad appeared in Glasgow newspapers for a device that was guaranteed to “cut your electricity bills in half”. 

Those who parted with their money found the device did exactly that.  It was a pair of cheap scissors. 

Maybe P.T Barnum was right?

  © 2009 Microphone Magic