Anybody have a good antenna design for the new UHF digital TV
stations?

I get reasonable results from my old VHF/UHF antenna (55% signal
strength) , but it's big and ugly, and I want to replace it with a
smaller, more efficient UHF design (maybe a Yagi) I can construct at
home.

Anybody know the dimensions of such an antenna, probabaly in the
frequency range of 400-800 Mhz ?

-Bill

On Sun, 15 Feb 2009 21:59:13 -0800 (PST), Bill Bowden
wrote:

Anybody have a good antenna design for the new UHF digital TV
stations?

I get reasonable results from my old VHF/UHF antenna (55% signal
strength) , but it's big and ugly, and I want to replace it with a
smaller, more efficient UHF design (maybe a Yagi) I can construct at
home.

Rule of thumb: The bigger and uglier the antenna, the better it works.

Anybody know the dimensions of such an antenna,

Various commercial digital TV antennas:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
with Eznec NEC2 files at:
http://www.hdtvprimer.com/SIMS/

probabaly in the
frequency range of 400-800 Mhz ?

There are going to be some DTV stations in the VHF range. You might
want to check the new channels for your area:
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-07-138A2.xls
List of frequencies:
http://en.wikipedia.org/wiki/North_American_broadcast_television_frequencies
Note that the upper end of the UHF TV band will be channel 51 at
698Mhz.






--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...
On Sun, 15 Feb 2009 21:59:13 -0800 (PST), Bill Bowden
wrote:

Anybody have a good antenna design for the new UHF digital TV
stations?

I get reasonable results from my old VHF/UHF antenna (55% signal
strength) , but it's big and ugly, and I want to replace it with a
smaller, more efficient UHF design (maybe a Yagi) I can construct at
home.

Rule of thumb: The bigger and uglier the antenna, the better it works.

Anybody know the dimensions of such an antenna,

Various commercial digital TV antennas:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
with Eznec NEC2 files at:
http://www.hdtvprimer.com/SIMS/

probabaly in the
frequency range of 400-800 Mhz ?

There are going to be some DTV stations in the VHF range. You might
want to check the new channels for your area:
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-07-138A2.xls
List of frequencies:

http://en.wikipedia.org/wiki/North_A...ion_frequencie
s
Note that the upper end of the UHF TV band will be channel 51 at
698Mhz.


Many good all-channel antennas exist but the absolute best-performing
antennas are limited to covering one band, sometimes just a portion of one
band. (This idea started a lot of do-it-yourself antenna projects.)

If you determine that you have some stations on VHF and some on UHF,
consider having more than one antenna. In a home where I lived in the
pre-cable days, I had four different antennas.

Of note: The bigger the antenna, the more likely it will be highly
directional. If you expect to receive weak stations from more than one
direction, you'll probably need either a rotator or more than one antenna.
It's probably better to connect multiple antennas through an A/B switch,
rather than combining them.

In article ,
Jeff Liebermann wrote:

On Sun, 15 Feb 2009 21:59:13 -0800 (PST), Bill Bowden
wrote:

Anybody have a good antenna design for the new UHF digital TV
stations?

I get reasonable results from my old VHF/UHF antenna (55% signal
strength) , but it's big and ugly, and I want to replace it with a
smaller, more efficient UHF design (maybe a Yagi) I can construct at
home.

Rule of thumb: The bigger and uglier the antenna, the better it works.

Anybody know the dimensions of such an antenna,

Various commercial digital TV antennas:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
with Eznec NEC2 files at:
http://www.hdtvprimer.com/SIMS/

probabaly in the
frequency range of 400-800 Mhz ?

There are going to be some DTV stations in the VHF range. You might
want to check the new channels for your area:
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-07-138A2.xls
List of frequencies:
http://en.wikipedia.org/wiki/North_American_broadcast_television_frequencies
Note that the upper end of the UHF TV band will be channel 51 at
698Mhz.

EXACTLY, after conversion, some VHF stations will return as Digital, a
few low-band and many high-band

--
--------------------------------------------------------
Personal e-mail is the n7bsn but at amsat.org
This posting address is a spam-trap and seldom read
RV and Camping FAQ can be found at
http://www.ralphandellen.us/rv

Bill Bowden wrote:
Anybody have a good antenna design for the new UHF digital TV
stations?

I get reasonable results from my old VHF/UHF antenna (55% signal
strength) , but it's big and ugly, and I want to replace it with a
smaller, more efficient UHF design (maybe a Yagi) I can construct at
home.

Anybody know the dimensions of such an antenna, probabaly in the
frequency range of 400-800 Mhz ?

-Bill

You could just cut off the long VHF elements and use them, cut to UHF
size, to extend and increase the number of director elements.

MTV

On Mon, 16 Feb 2009 00:32:22 -0800, "Sal M. Onella"
wrote:

Many good all-channel antennas exist but the absolute best-performing
antennas are limited to covering one band, sometimes just a portion of one
band. (This idea started a lot of do-it-yourself antenna projects.)

Sure. I can always trade bandwidth for gain. If you only watch one
DTV station, a single channel antenna is a good idea, especially if
it's distant and weak. If you don't like rotators, perhaps a
collection of single channel antennas pointed at each station might be
useful. I live in the mountains where reflections are a problem for
OTA reception. For a time, I was building and selling custom single
channel TV antennas, with built in preamps. They worked great, but
when Comcast started offering $13/month for local only TV, I gave up.

If you determine that you have some stations on VHF and some on UHF,
consider having more than one antenna. In a home where I lived in the
pre-cable days, I had four different antennas.

Same here. Back in the 1970's, I lived in Israel for a while. In the
cities, everyone lived in big apartment complexes. Nobody watched the
official Israeli stations. The good programming was on the various
Arab stations, which were diverse, distant, and politically incorrect.
There was no cable TV (because the government didn't want to make it
easy to watch the Arab stations) so every apartment had its own
collection of antennas. Typical was a 3 meter pole with at least 4
yagis. Multiply that by at least 4 apartments per building and the
roof tops looked like an aluminum forest. Somewhat later, I lived in
Smog Angeles where everything is on Mt Wilson. Only one antenna
needed.

Of note: The bigger the antenna, the more likely it will be highly
directional.

http://groups.google.com/group/rec.radio.amateur.antenna/msg/8535c986a167ac41
"small - efficient - broadband: pick any two."
Roy Lewallen, W7EL

I've dealt with some rather monstrous log periodic directional
antennas. They cover the entire HF spectrum, but only have about 4dBi
of gain at any frequency. Directionality is about what you would
expect for a 4dBi antenna (about 80 degrees -3dB beamwidth). Just
because it's big, doesn't mean it has gain or a narrow beamwidth.

The same thing applies to TV antennas. If you compromise on the
bandwidth by reducing the number of channels it covers, then you can
get some more gain and narrower beamwidth (for a given size). That
seems to be what's happening as the highest frequency goes from 900 to
700MHz. However, that's not going to make a huge difference is size
of gain. More useful is ignoring the VHF channels and making the
antenna UHF only. That really reduces the size of the antenna or
increases the gain (for a given size antenna).

If you expect to receive weak stations from more than one
direction, you'll probably need either a rotator or more than one antenna.

True. I once was involved in building direction finders. I got
greedy and decided to find a commercial application. What the world
needed was a direction finder tied to a rotator and yagi. The yagi
would automatically rotate to the direction of the strongest signal. I
first tried it with a TV antenna and it worked. Unfortunately, my
pre-microprocessor circuitry did not have any way to distinguish
between multiple peaks in the signal strength as well as antenna side
lobes. It would often pick the wrong lobe. Making a 360 degree scan
would solve this problem, but that increased the complexity beyond
acceptable limits.

So, I decided that perhaps it might be useful for commercial two-way
radio. I installed one on a mountain top site on a UHF commercial
frequency. Useful range was dramatically increased for the repeater.
However, during a typical conversation, the antenna would rotate back
and forth between each mobile and base. Commodity antenna rotators
are not designed for near 100% duty cycle. It was also a dice toss as
to whether a mobile could be heard, depending totally on the current
antenna orientation. I could have improved things with a better and
faster motor, but didn't. I know a bad idea when I design one.

I also built an omnidirectional TV antenna designed to be hung near
the top of the local 50 meter redwood and fir trees. There was enough
vertically polarized TV signal to make it usable. However, it also
picked up reflections from every possible direction, resulting in
multiple obnoxious ghosts. Bad idea, but fun to try.

It's probably better to connect multiple antennas through an A/B switch,
rather than combining them.

Yep. If the signals from multiple antenna could just as easily cancel
as they could add. However, if you installed a band pass filter
between the antenna and the combiner, the signals from one channel
will only appear on one port, thus eliminating any chance of
cancellation. I would filter and combine.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

Same here. Back in the 1970's, I lived in Israel for a while. In the
cities, everyone lived in big apartment complexes. Nobody watched the
official Israeli stations. The good programming was on the various
Arab stations, which were diverse, distant, and politically incorrect.
There was no cable TV (because the government didn't want to make it
easy to watch the Arab stations) so every apartment had its own
collection of antennas. Typical was a 3 meter pole with at least 4
yagis. Multiply that by at least 4 apartments per building and the
roof tops looked like an aluminum forest.

Those days are gone, we have cable TV, DBS TV and streaming video on the
Internet. In the cities the antennas remain, no one wants to pay the money
to remove them. Eventually it will be necessary to repair the roofs under them
and take them down.

We are also supposed to have digital terrestrial TV in a few months, but instead
of each station having various programs, there will be multiple channels
on the same frequency.

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Jeff Liebermann wrote:
If you don't like rotators, perhaps a
collection of single channel antennas pointed at each station might be
useful.

Are the GPS coordinates for the transmitting antenna
available anywhere? I called the local TV station
and they don't know the coordinates for their
transmitting antenna.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:

Are the GPS coordinates for the transmitting antenna
available anywhere? I called the local TV station
and they don't know the coordinates for their
transmitting antenna.

I'd be surprised if they gave them to you if they had them. Publishing the
exact location may be a security risk.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Cecil Moore wrote:
Jeff Liebermann wrote:
If you don't like rotators, perhaps a
collection of single channel antennas pointed at each station might be
useful.

Are the GPS coordinates for the transmitting antenna
available anywhere? I called the local TV station
and they don't know the coordinates for their
transmitting antenna.

I'm not sure what "GPS coordinates" means, but this site will draw you a
map and give you regular coordinates:

http://www.fccinfo.com