New amplified antenna versus old one.

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".

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).

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.

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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.

Sorta. The top end of the UHF band (ch 52-83) is now mostly land mobile. UHF TV is now ch 14-51.

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.

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

Here's the article on the GPS interference problem:

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.

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

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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.