What is This Antenna?
Paul Zander, AA6PZ
This work is licensed under a
3.0 Unported License
A friend had what he thought was a UHF TV antenna, but wasn't sure
to connect it.
Near the middle of the antenna are a pair of wing nuts. This is
"obviously" where the feedline would connect. There are a pair of
heavy wires parallel to the boom, and a short section of 300 Ohm
lead that looks like it was installed at the factory. There is
no direct connection between the "feed assembly" and any of the
elements. I modeled the antenna with EZNEC. Not surprisingly, it did
As an experiment, I
changed the model to make element 7, counting from the left as 1,
driven element. This resulted in a model of a Yagi antenna with
approximately 10 dBi gain from 440 to 500 MHz. The antenna is
years old, when UHF TV covered
470 to 800 MHz, this antenna was not intended for TV usage.
So what was the original purpose of this antenna? What is
to make a connection between the feedline and the elements?
The answer came from Bob, K8YS in
He recalled that around 1980 there was a "pay to view" TV
service. They broadcast on a UHF TV channel, but "scrambled"
the signal. They sold a package with the decoder box and a
After receiving his email, I recalled that in the San Francisco
area, there was a similar service. And it used a channel that
matches the frequency coverage of this antenna. Two sets of
terminals would make it easy to connect in with the roof-top
antennas that most people used at that time before cable.
In both Cincinnati and Silicon Valley, there were so many
electronics companies that home-brew decoders were widely made and
distributed to friends and neighbors. The "service" only
lasted a few years.