Your goal is to connect the antenna.
You look at the antenna connector, and "decode" the specification
for the antenna by looking at it.
A poorly constructed antenna, will use the wrong connector, and
cause the user to select the wrong equipment to go with it.
For example, I have a T-shaped FM antenna, and I think it came
with the wrong connector on the end. If I had a T shaped FM
antenna with twin lead, I'd cut off whatever was on the end, strip
and clean the two wires, and screw them to a Balun. That
would do the 300 ohm to 75 ohm conversion (preserving as
much of the signal as possible).
Virtually any (unbalanced) wire shoved into the central pin on
the tuner will do something. But, you lose the ability to orient
the antenna in a useful way ("point it to the transmitter"). Some
of the commercial TV antennas, they have a 15 to 20 degree beamwidth,
and you can use the tight beam of the antenna, to avoid interference
sources which are off-axis.
So all of this faffing about, is to lend some order to the
randomness of single wire antennas. We want an antenna with
predictable properties. Even the rabbit ears, you can aim
it, and adjust the length of the ears, for the frequency of
interest.
For example, when I built my own antenna (one designed by
someone who lives in the same city as me), that antenna
has a tight beamwidth, and since transmitters are on
three different compass points here, I can't pick up all
the stations at once without rotating the antenna. That's not
very practical. But, the high gain of the antenna, is supposed
to help with distant stations (like the station downtown here,
with a puny 3kW transmitter). Using the Balun and proper hookup,
saves a couple dB on losses, so the 15dB I paid good money for,
is not degraded. Making your own antenna is not cheap, unless
you have a discount hardware store nearby. My antenna used
50 feet of 1/4" copper tubing, unrolled and straighted into
elements. The guy who designed it, was a software guy, and he
wrote an optimizer for his design. It ran on his computer
for a solid week, adjusting element lengths, until it had
a relatively flat frequency response.
His antenna design, has the performance of this one, only
this one has phase reversals at VHF frequencies. It means
this antenna cannot pick up digital TV on a couple of the
low channels (between 7 and 13). It's not clear, why our
Department Of Communications continues to support VHF. All
the digital channels could have been assigned in UHF frequencies,
which would have simplified antenna designs. Someone wanting
OTA TV here, they need an antenna covering VHF and UHF, and
that makes the antenna twice as complicated. Some amateur
antenna designers analysed this with 4NEC2, to figure out
what happens at VHF frequencies. At a couple frequencies,
the lobes of the antenna point backwards.
http://www.thesource.ca/estore/prod...ine&category=Outdoor+Antennas&product=1519124
You can see that antenna has its own Balun in the center
of the antenna. You can't see the connector on the end, but
there might be an F-series on the end, suited for direct
connection to your tuner. In practice, a length of cable
TV wire, and a female-to-female F-series will likely
be needed, to wire it up.
The same antenna is sold on this site, as a kit. In this case,
it's intended for mast mounting. The preamp in the picture,
compensates for loss in the feed cable, when it runs a hundred
feet to your room. If you install on a mast, it has to be
secure, as well as take into account grounding requirements
if the mast is hit by lightning. It's just easier with
that antenna, to avoid the preamp and mast altogether,
and just use it in the house, next to a window. Even
if you lose 6dB in the process. It's just safer.
http://angelelectronics.ca/shop/ota/outdoor-antennas/65mi-105km-over/channel-master-cm4228-combo
In the city, you don't need that, because the stations
are so strong. In that case, the rabbit ears will pick
up all the stations that may be available. When I
started my antenna project, it was intended for the
cottage. Which is a "fringe" installation, and needs
the gain. All the stations within range of the cottage,
sit on the same antenna tower (on a hill many miles away),
and so the antenna will never need to be rotated.
Paul
