Line of sight is very important. If the hill is big enough, it can
completely block the signal. As I mentioned, a big high gain antenna
does nothing if there's no signal to receive. I can run the numbers
for you if you send me the station call sign, your EXACT lat-long, and
the proposed height above the ground. Something like this:
<
http://802.11junk.com/jeffl/coverage/RST/>
The catch is that I'm rather busy during the holiday madness month and
may not have much time to do it right. If you want to try it
yourself, you can do a fair job with Google Earth.
Reading between the lines, are you proposing to build an indoor TV
antenna? If so, that will limit the size of the antenna boom. It
would still be worthwhile, but not as much as simply putting the
antenna on the roof. Think of devious ways you can install a rooftop
antenna. I recently built a yagi out of sheet mylar and aluminum duct
tape. It worked.
Also, if you do it indoors, you will not have much feed line. The
purpose of the antenna mounted amplifier is mostly to compensate for
the losses of the coax cable between the antenna and receiver.
However, if the coax cable is short (less than 10m) don't bother with
the amplifier.
Indoor antennas through glass has another problem. The IR reflective
coating found on all new construction windows is quite effective at
blocking RF signals. That's another reason for a roof mounted
antenna.
I'm trying to forget. There was more garbage sold as converters than
I ever saw in my worst nightmare. Fortunately, most of those were
either trashed, recycled, or sold on eBay.
The channel number has been virtualized allegedly in order to prevent
user confusion. Of course, it did quite the opposite. At this time,
the channel number has NOTHING to do with the actual transmit
frequency. Various frequency lists will have both the indicated
channel and the real transmit channel.
The Zenith DTT901 is actually one of the better converters. The
limiting factor on almost all of them is receive sensitivity but the
Zenith box was better than most.
Any proper antenna is better than rabbit ears and a loop.
That's why I suggested building a crude wooden prototype before diving
into a proper constructed version. If the rabbit ears are as bad as I
suspect, anything will gain will make a substantial improvement.
However, there's nothing sacred about building a yagi. It just
happens to be fairly easy to build and delivers lots of gain. There
are plenty of other designs that work. Try a Gray Hoverman antenna:
<
https://www.google.com/search?q=gray+hoverman+antenna&tbm=isch>
$100 without any mounting hardware or coax. Add a few dollars for
those. I just was forced to buy a 10ft 1.25" mast at Radio Shock. $32
each. OUCH!
<
http://www.radioshack.com/product/index.jsp?productId=3739599>
Oh swell. The price went up for Christmas.
Incidentally, you can compare many commercial antennas at:
Yep. That's the suggested plan.
All elements are one piece except the driven element. However, you're
not going to be building it like the typical yagi calculator shows.
It's not going to be a simple dipole. Build a folded dipole instead.
The feed point will (hopefully) be about 300 ohms. At the feed point
attach a 300 ohm to 75 ohm balun, and then the coax cable to the TV.
One of these things:
Yes it matters and no it's not a simple 1/2 wave dipole. With a
folded dipole, the 300 ohm feed point is at the wire ends.
A few more details... I suggested building a single channel yagi
instead of a broadband antenna because it's easier and because it
delivers more gain. If you build the yagi from any of the online
calculators, you'll end up with a fairly narrow band antenna. The
more elements, the narrower the bandwidth. When the bandwidth starts
to approach that of the TV channel (6MHZ) you're going to run into
critical design parameters and cut dimensions that can't be worked out
by trial and error. So, don't make it with too many elements and you
should be ok. Otherwise, borrow an antenna analyzer that covers the
frequency range, a reflection coefficient bridge with sweep generator,
a network analyzer, or some manner of RF test equipment that can
determine if you've hit the correct tuning frequency.
A rough guess as to bandwidth for the single channel yagi would be
about 15% or about 90MHz (see bottom graph) so you should be ok.
<
http://www.supernec.com/yagi.htm>
Here's an antenna a friend built:
<
http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
It should work, but doesn't. Note the creative use of hardware store
materials.
--