Old antenna for new tv

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On 9/2/2010 12:51 PM, mm wrote:

I'll guess that you had to chase the tuning up the band because the superregenerative oscillator in the Hallicrafters was drifting as the tubes warmed up the resistors and capacitors in the circuit. I don't know enough to even guess how you were picking up an FM audio signal on an AM receiver unless the transmitter was broadcasting some sort of spurious subharmonic that was amplitude modulated or unless the FM signal and the IF section of the receiver created a beat frequency (analagous to tuning in a single side band audio signal).
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wrote:

I have to take time to read this. It looks complicated.
It is, however, the first thing I've read that at all addresses what I asked about elsewhere, about waves received by elements that bend and go in the oppoosite directino, about the waves cancelling each other out.
Well, actually they refer to this in a much different context, iiuc, but I'm please that it says anything at all. I only have a little bit of theory and a tiny bit of practice, and when I get an idea, I'm glad to see it's not crazy.
Nonessential reading: Question: How does the energy collected by the directors get to the cable? Answer: It is re-radiated to the driven element as normal radio waves.
Question: Why dont the re-radiated waves go backward or laterally? Answer: Because all the directors cancel each other in those directions.
Question: Why dont these re-radiated waves prevent the diffraction of incident waves inward toward the boom? Answer: Because the phase of the re-radiated waves has been changed by about 90 degrees, so they neither subtract nor add to the incident waves.
Question: How did the director currents get changed by 90 degrees? Short answer: The element lengths control this. The director currents are shifted -90 degrees while the reflector current is shifted +90 degrees.
Long answer: This graph shows how the current induced in a rod is affected by the length of the rod. The phase changes quickly with a small change in element ....

Not sure what you mean here. Are you talking about the antenna the OP brought up. It does have an amp after all.
If you're not talking about that, pelase explain a little.

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On 9/2/2010 1:08 PM, mm wrote:

<snip>
I Googled a bit and that seemed about right. It does seem to cover a lot for one page! I'll have to read it now myself!

Those are some answers!

Without the amp. Probably just a couple dB on VHF.
Jeff

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wrote:

"Any Color Code - This large directional antenna can be used in any color code specified on AntennaWeb.org "
Yeah, you can use it, but will it work? I wish they had phrased this differently, or maybe they knew exactdly what they were doing and phrased it just so so they couldn't be charged with lying.
I forget what the 7th color is but if this antenna will bring in signals from that range, I'll eat my hat.
This is all they say about tmiles.
"This long range digital outdoor HD TV antenna has been known to pick up stations that are around 150 miles away. We have had customers call and tell us how happy they were with their antenna because they were able to pick up stations up to 150 miles away. We have even had customers tell us they were able to pick up US broadcasts from Canada. So we are very confident that this antenna will work for you."
Baloney. Because of the curvature of the earth, no one can get tv from 150 miles away unles somewhere there is a transmitting antenna many times higher than any near you. They amaybe talking about people who live 150 miles from the CN Tower, which is the 3rd highest tower (that is, including tall buildings) in the world, 1815 feet. Do you live within 150 miles of Toronto? If not, forget it.
It's getting late for me, butyou can check this out.
http://www.google.com/#num 0&hl=en&newwindow=1&q=cn+tower+tv+channels&aq=f&aqi=g1&aql=&oq=&gs_rfai=&pbx=1&fpba7271bf89c8c4
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mm wrote:

http://www.google.com/#num 0&hl=en&newwindow=1&q=cn+tower+tv+channels&aq=f&aqi=g1&aql=&oq=&gs_rfai=&pbx=1&fpba7271bf89c8c4
Getting stations from more than 150 miles away reliably and repeatedly may be impossible, but it DOES happen. E-layer reflections, IIRC, is what allows it. Under certain conditions, the cloud layer creates a tunnel of sorts that can carry signal past line of sight. I used to get it often in analog days, but have only noticed it once since the switch to digital. And that was with one of those powered indoor antennas, placed in a window. I'm in SW MI, two counties in from the big lake. I was playing with the converter box, and told it to auto-search. For about 4 hours, I was getting a station in Milwaukee WI, clear as a bell.
I also need to replace what is left of my rooftop antenna, but have been procrastinating it for several years, since it would involve crawlspace time replacing cable runs. So when BigLots had the powered indoor antennas on sale for 20 bucks, I figured 'what the hell', and actually have had surprisingly good results with it. I can't get all the stations I want to get, but I can get the big 4 networks reliably, with a little trial and error turning the camera tripod I have the antenna sitting on.
(No, no SWMBO lives here. Why do you ask?)
--
aem sends...

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Not necessarily true. If you live on a hilltop 300' higher than the average terrain around you, you have greatly increased your line of sight distance to the horizon. Therefore you could pick up stations your friends below you could not receive. That is why these antenna range sales pitches do not tell you what the conditions were.
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wrote:

Okay. My error. But you could get the same results in this unusual situation with any good antenna, maybe any antenna at all.
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IF IT IS A ROOF TOP OR EXTERIOR MODEL YOU CAN JUST ADD AN INLINE SIGNAL BOOSTER TO YOUR EXISTING ANTENNA THE MORE DB GAIN THE BETTER AN ANTENNA ROTOR PLUS THE AMP WILL KICK BUT BECAUSE YOU CAN ROTATE THE ARRAY AND HONE IN THE SIGNAL
INTERIOR RABBIT EARS WITH OUT AMPLIFICATION ARE INSUFFICIENT THOUGH SOMEWHAT EFFECTIVE DEPENDING ON SIGNAL STRENGTH IN YOUR AREA AND HOME
IAP
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On 9/1/2010 10:05 PM, Jdog wrote:

It all depends on your situation. If that one is expensive it probably isn't worth it. I have 2 antennas in the attic. I have a largish yagi that pulls in the main local channels just great. They are all in about the same direction. But it does a poor job on channels to the side. So I made up one with a folded dipole vhf antenna and a bowtie uhf antenna. I mounted them in the attic with the folded dipole pointed at the main stations and the bowtie pointed at 90 degrees, so it could pick up the college station at Claremore. That is about 35 miles away, and it comes in fine. I do get an occasional drop out, which I suspect is a plane flying through the pattern. The folded dipole pointed at the major channels gets a good signal, but has more drop outs. I suspect that is because the signal path is right over a busy freeway, and trucks stick up high enough to cause reflections. You may have some or all of these conditions.
I have cable so I didn't really need these, but I wanted to be able to get the signal off the air for bad times when the cable might be down (bad weather and such). Then I wanted the Claremore station because at the time they were showing Classic Arts Showcase 24 hours a day on the sub channel.
Bill
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Here're my three cents - until you read a review of that antenna where someone puts it through its paces against a better known model, and shows that it does a good job, you should probably avoid it.
Here's a place that has been in business quite a while, and provides good customer support. They also put up a decent amount of technical info about most of their antennas, and have fair shipping prices. I bought a Winegard 9095 ($69 plus ship) from them a while back, and was able to pull in stations from Cincinnati and Columbus here in Dayton, as well as a few from Indiana. Pretty cool pulling in twenty some stations. That was with an amplifier, though, and a lot depends on your tuner. I was getting about 8 fewer stations with another digital tuner.
specs: http://www.starkelectronic.com/wca9095.htm (averages about 15db gain up to channel 50, then down to about 12db
BTW, the Channel Master 4251 parabolic antenna is widely viewed as the best UHF antenna ever made. They sold for between $150-$200 new, and were discontinued in 2001. Some info:
http://www.rocketroberts.com/cm4251/cm4251.htm
>I'm suspicious of the stats for the "new", 35 dB is very high. Built in >preamp?
I agree - those numbers seem so high that I'm guessing it is just "technospeak" to reel people in, and not realistic. What you need is a graph showing the actual dB gain at various channels. Good manufacturers make those available, so that people can see the actual gain and decide if an antenna is right for them.
Regarding not being able to get a TV station from 150 miles away - it really depends. I live near Dayton, Ohio. While a few years back I had my antenna mounted up above the roof, for the past year or so I had it mounted off the lattice on our front porch. Yes, it was about 10' off the ground. I was able to occasionally pull in stations 50 miles away. One day, in the middle of the night, I was getting in a station from Louisville, Ky. That's right about 150 miles, and it was crystal clear. When I was a kid living near Lima, OH, my dad could use the antenna rotor and pull in a station from Toronto a lot of nights.
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On 9/1/2010 11:05 PM, Jdog wrote:

The old style antenna will work (with HD and digital) just as good today as it did 50 years ago. Actually they seem to work much better with the switch to digital. The ones the link points to... well they might work, but none of the ones I tried (and returned)worked well. Now an old fashioned type with a pre-amp out near the antenna and possibly another amp near the TV, that will work better that that *gimmick* one at the link.
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On 9/1/2010 10:05 PM, Jdog wrote:

Antennas, the 20/80% rule applies. You can get a lot of results with not to much work when it comes to antennas. In your case a lot depends on what channels you are going to want. UHF antennas are the ones with the short elements. VHF is the long ones. Work backwards, find where the signal you want to catch is coming from and the strength and then you get the antenna that will do the job. The wiring from the antenna to the TV is also very important and the number of splitters on the line. Catch the signal and get it to the TV is what it's all about. The antenna you found is actually rated quite good but it is UHF only, I read somewhere it was made for the Australian market and now it's imported to the US. If you go this way they are a lot cheaper on e-bay. There must be 100 dealers selling them. There are a lot of how to do clips on youtube. If the signal is strong enough in your area you can make your own. I recently dropped DISH and now use OTA and the cable modem to stream to the TV. The towers are 70 miles from my house. I get about 30 channels OTA and watch CNBS, Bloomberg, CNN and a few others with live streaming. Here ya go, one of the better sites I found when I was putting up my antenna, which is a beat up old one my neighbor gave me but it gets the job done. Most maybe all digital TV's have a signal strength meter use that to aim the antenna. http://shop.ebay.com/?_from=R40&_trksid=p3907.m570.l1313&_nkw=tv+antenna&_sacat=See-All-Categories and must reading for the home TV antenna enthusiast, links to tower locations and signal strength from them. http://tvfool.com /
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