New amplified antenna versus old one.

[mm]

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

AIUI, the tv frequencies are still VHF and UHF, the same as before.
But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?

 

[Sjouke Burry]

mm wrote:

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

AIUI, the tv frequencies are still VHF and UHF, the same as before.
But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?
Here in the Netherlands we switched to digital and vertical antenna

polarization at the same time, in which case the old ones needed
re-orientation.
And sometimes "new chinese" is not always better than "local old".

 

[Dave Platt]

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

You'll need to define *which* new amplified antennas you're referring
to, *which* old ones, and *what* you mean by "better".

It's possibly true that there are better RF transistors available for
this sort of application today than a couple of decades ago. However,
I doubt that they're all that much better in terms of their gain,
noise level, or signal handling qualities. They're probably less
expensive than those of yesteryear.

I think that the quality of the design of the amplifier as a whole is
going to make more of a difference than the specific year in which it
was made. A lot of TV-antenna amplifiers are simply *miserable* -
they're a simple one-transistor broadband design, with no tuning, poor
bypassing, and lousy strong-signal handling capability. Hit 'em with
a strong RF signal anywhere in their passband, and they'll saturate,
start generating intermodulation products, and so forth. Some have
been notorious for breaking into spontaneous oscillation, and
interfering with nearby radio reception (or even GPS - a couple of bad
active antenna systems on boats in the Moss Landing harbor in
California wiped out GPS reception for several miles, posing a real
safety hazard).

AIUI, the tv frequencies are still VHF and UHF, the same as before.
But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?

I'd expect not.

The full (old, legacy) TV frequencies range from 54 MHz (channel 2,
bottom of VHF low band) all the way up to 890 MHz (CHannel 83).

In more recent years, the 800 MHz spectrum was pulled back, leaving
only the 54 MHz - 794 MHz range.

The new DTV transition has reclaimed the 700 MHz band. So, today, a
full-range amplified TV antenna must handle 54 MHz up to 698 MHz.

That's not all that much of a narrowing, and (as I said above) most
TV-antenna amplifiers aren't tuned. Interference signals are as
likely as not to be in the middle of their passband (e.g. ham, police,
fire), and the amplifiers usually do *not* have traps to keep out the
non-TV frequencies.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Jeff Liebermann]

On Fri, 17 Jul 2009 18:22:45 -0400, mm <NOPSAMmm2005@bigfoot.com>
wrote:

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

Better for doing what? The newer amplifiers, such as Channel Master
7777 have seperate VHF and UHF amplifier sections, which helps with
the sensitivity, dynamic range, gain, and antenna size requirements.
For example, you can combine a seperatge VHF and a seperate UHF
antenna on one mast with this amplifier. It's not a huge improvment,
but it's useful in fringe areas in keeping the length of the yagi
within reason.

AIUI, the tv frequencies are still VHF and UHF, the same as before.

Sorta. The top end of the UHF band (ch 52-83) is now mostly land
mobile. UHF TV is now ch 14-51.
<http://en.wikipedia.org/wiki/North_American_broadcast_television_frequencies>

But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?

Yep. You can always trade bandwidth for gain. The original UHF band
was 470-896MHz. The new UHF band is 470-698MHz for a net loss of
about 200MHz. That's not a huge change in bandwidth.

Whether you need the added gain also depends on what you're trying to
accomplish, how weak a signal you're attempting to amplify, how much
coax cable loss you're trying to compensate, and a few other factors.
In most cases, the antenna mounted amplifier has too much gain.

 

[isw]

In article <a9u16555s9qvkib85lc89qm77rcq4mpjjn@4ax.com>,
mm <NOPSAMmm2005@bigfoot.com> wrote:

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

AIUI, the tv frequencies are still VHF and UHF, the same as before.
But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?

There's a characteristic of RF amplifiers -- "phase noise" -- which is
not particularly important for analog signals, but which can be a big
problem for digital. IF the amplifier in the antenna has high phase
noise, then it *might* matter.

Isaac

 

[Jeff Liebermann]

On Fri, 17 Jul 2009 16:00:31 -0700, dplatt@radagast.org (Dave Platt)
wrote:

I think that the quality of the design of the amplifier as a whole is
going to make more of a difference than the specific year in which it
was made. A lot of TV-antenna amplifiers are simply *miserable* -
they're a simple one-transistor broadband design, with no tuning, poor
bypassing, and lousy strong-signal handling capability. Hit 'em with
a strong RF signal anywhere in their passband, and they'll saturate,
start generating intermodulation products, and so forth. Some have
been notorious for breaking into spontaneous oscillation, and
interfering with nearby radio reception (or even GPS - a couple of bad
active antenna systems on boats in the Moss Landing harbor in
California wiped out GPS reception for several miles, posing a real
safety hazard).

Here's the article on the GPS interference problem:
<http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=43404>
I've had to deal with antenna mounted oscillating amplifiers
interfering with ham radio, commercial radio, and TV/FM. If it can
amplify at some frequency, it can also oscillate at that frequency.
The worst was tracking down an intermod problem at a local repeater
site. The TV amplifier would only oscillate when the repeater xmitter
was on the air. Lots of fun trying to track that one down. The good
news is that I have yet to see a fairly modern TV/FM antenna mounted
amplifier cause a problem. The one's I've found causing problems are
the cheap junk sold at trailer supply houses, marine supply houses,
and on eBay. Name brand seems to work well. Note that the ones found
by MBARI in the article were mast top integrated TV antennas with a
built in amplifier, not an add-on amplifier.

That's not all that much of a narrowing, and (as I said above) most
TV-antenna amplifiers aren't tuned. Interference signals are as
likely as not to be in the middle of their passband (e.g. ham, police,
fire), and the amplifiers usually do *not* have traps to keep out the
non-TV frequencies.

I use 1/4 wave coax stubs to do some minimal notching. FM broadcast
overload is most common. The problem is that the notch filter really
should be installed between the antenna and the amplifier, not after
the amplifier. That means trimming the cable on top of the tower. No
fun.

 

[Allodoxaphobia]

On Fri, 17 Jul 2009 21:42:52 -0700, Jeff Liebermann wrote:

I use 1/4 wave coax stubs to do some minimal notching. FM broadcast
overload is most common. The problem is that the notch filter really
should be installed between the antenna and the amplifier, not after
the amplifier. That means trimming the cable on top of the tower. No
fun.

Never forgetting, of course, that a 1/4 wave suck-out trap also works at
all odd-multiple frequencies.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

 

[mm]

On Fri, 17 Jul 2009 16:00:31 -0700, dplatt@radagast.org (Dave Platt)
wrote:

A friend has been told that new amplified tv antennas are better than
old ones. Is that true.

You'll need to define *which* new amplified antennas you're referring
to, *which* old ones, and *what* you mean by "better".

Old would be anything one or her friends might have lying around the
house, but I don't know what that would be.

New would be whatever they are selling now, but then again, they are
selling a lot of things.

Better would be getting more channels.

Both my friend, who lives in a basement apartment, and his landlady
and friend, who lives upstairs, have pretty much gotten along without
tv since June whatever. They have converter boxes but very few
channels. I haven't been there yet though. I only know she has an
attic, but i don't even know if it is finished or not, or if there is
a stairs or a hole in the ceiling, I don't even remember if it is a
one or two story house below the attic.

I'm thinking maybe they can share one probably new amplified antenna,
but I at least want to see how they do with one of my old ones first.

Based on what you say, it seems like being new is no guarantee of
being better than old. I'm hoping to go over there some day this
coming week and see the situation.

Also, based on an email from the landlady my friend forwarded me, he
seems to have given an old antenna to her, and she asked how old it
was, and said she was told new was better. I will learn more about
all of this when I go there, but thanks for the info to go with what I
see there..

Thanks to all of you.

It's possibly true that there are better RF transistors available for
this sort of application today than a couple of decades ago. However,
I doubt that they're all that much better in terms of their gain,
noise level, or signal handling qualities. They're probably less
expensive than those of yesteryear.

I think that the quality of the design of the amplifier as a whole is
going to make more of a difference than the specific year in which it
was made. A lot of TV-antenna amplifiers are simply *miserable* -
they're a simple one-transistor broadband design, with no tuning, poor
bypassing, and lousy strong-signal handling capability. Hit 'em with
a strong RF signal anywhere in their passband, and they'll saturate,
start generating intermodulation products, and so forth. Some have
been notorious for breaking into spontaneous oscillation, and
interfering with nearby radio reception (or even GPS - a couple of bad
active antenna systems on boats in the Moss Landing harbor in
California wiped out GPS reception for several miles, posing a real
safety hazard).

AIUI, the tv frequencies are still VHF and UHF, the same as before.
But then I started to think that maybe they were in a narrower band
than before, and an amplifier tuned to this narrower band could work
better than an old amplified antenna meant to work over the entire
VHF/UHF band. Any truth to this fanciful idea of mine?

I'd expect not.

The full (old, legacy) TV frequencies range from 54 MHz (channel 2,
bottom of VHF low band) all the way up to 890 MHz (CHannel 83).

In more recent years, the 800 MHz spectrum was pulled back, leaving
only the 54 MHz - 794 MHz range.

The new DTV transition has reclaimed the 700 MHz band. So, today, a
full-range amplified TV antenna must handle 54 MHz up to 698 MHz.

That's not all that much of a narrowing, and (as I said above) most
TV-antenna amplifiers aren't tuned. Interference signals are as
likely as not to be in the middle of their passband (e.g. ham, police,
fire), and the amplifiers usually do *not* have traps to keep out the
non-TV frequencies.