The Select-A-Tenna has been sold through catalogs and in magazines for years, but it wasn't until 1994 that I read enough about it to take the plunge.
It looks very simple: an 11" disk of ABS plastic with a dial in the middle. What's really at work here is an inductive loop antenna system inside the disc which actually works as advertised: it enhances signals that come to your AM radio and nulls out what you don't want to hear.
The Select-A-Tenna is designed, developed, and manufactured by some scientists in Wisconsin. It uses no batteries or AC power, and requires no physical connection to your radio. Using the unit is very simple: just tune your radio to a weak AM station, set the antenna a couple inches away, then tune the knob on the front. You will be amazed at the improvement in reception!
Using the Select-A-Tenna on a radio like the Grundig Satellit 700 or the GE Super Radio II is serious business for a Medium-wave DXer. Using it on a radio like the GE 7-1600c is sort of like putting a rocket engine in a 1974 Chevy Vega: as fun idea, but more power than you really need.
In early 2014 I received a note from website visitor J. Brook, who found one of these units at a thrift store for $10! J opened up the Select-a-Tenna and took some photos and measurements of what was found inside. Here are J's notes:
measured by my BK Precision 875B LCR meter, along with the number of turns and the form diameter (22 turns on a 9.75" form).
One photo shows a label I made with the specs
One photo shows 2 segments of wire alongside thecoil wire. The smaller gauge wire is 22-gauge magnet wire. The larger gauge wire is 18-gauge hobby wire. I think the coil wire falls in between--which would make it 20 gauge.
(After I pried the back off, I had to build a newbase for the antenna. That's the mint green thing in the photos.)
My Select-a-Tenna was sold to a radio hobbyist in Indiana.
The Select-A-Tenna is available through most radio supply outlets. Another great investment!
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