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Old 6-Dec-2011, 11:19 PM   #1
jeffj318
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Question Who is right? My brother in law or me? HD antenna or not?

My brother in law said you need an HD antenna to get HD stations.
I said any roof top antenna would work as the signal depends on the TV whether it is HD or not. Who is correct?
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Old 7-Dec-2011, 12:13 AM   #2
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Originally Posted by jeffj318 View Post
My brother in law said you need an HD antenna to get HD stations.
I said any roof top antenna would work as the signal depends on the TV whether it is HD or not. Who is correct?
any antenna will catch HD . Even a pair of rabbit ears if you are close enough. Here is some info for newbies.

http://www.crutchfield.com/learn/lea...html?c=16&tp=3

http://www.dennysantennaservice.com/...lp_center.html
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Old 7-Dec-2011, 12:23 AM   #3
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Reception

There is No Such Antenna as a HD antenna. HD antennas were invented in marketing departments to sell more antennas. The point is easly proven because plain old rabbit ears indoor antennas will receive analog tv signals , Non HD digital tv transmissions and HD tv transmissions. 40 year old tv antennas that are in attics receive HD. 40 year old antennas that on the roof of the house and still in some kind of functional condition receive HD. A plain old wire coat hanger will receive analog tv transmissions , Non Hd digital tv transmissions and HD digital tv transmissions. The human body is a antenna that receives analog tv transmissions , Non Hd digital tv transmissions and Hd digital transmissions. The HD is on products because that is what people expect to see. Take the same antenna that has these two letters of the alphabet --> HD , and take that HD off the box and people will not by the antenna because there is no "HD" on the antenna box. What does that say about people that believe any thing with out even checking on the internet. All this stuff is easy to look up on the internet. Here are the tv picture resolutions ( the clarity of the picture ) , Low definition - 480i and 480P. High definition - 720P and 1080i and 1080P. The tv will also show you what signal is being transmitted and received , 480i , 480P , 720P , 1080i , 1080P. Perhaps you brother in law is goading you to get a rise out of you.

Last edited by Electron; 20-Oct-2012 at 3:04 PM.
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Old 7-Dec-2011, 12:32 AM   #4
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Originally Posted by jeffj318 View Post
My brother in law said you need an HD antenna to get HD stations.
I said any roof top antenna would work as the signal depends on the TV whether it is HD or not. Who is correct?
There is no such thing as an HD antenna. Digital television uses either all or a subset of the same channels used to broadcast analog television. That said, digital television has almost abandoned VHF channels below channel 7. In some markets, digital television is broadcast exclusively on UHF. Therefore, a UHF (14-69) antenna is the minimum requirement. In others, a High VHF-UHF (7-69) is required to receive all broadcasts. On those few areas where stations still broadcast on Low VHF, a full-spectrum VHF-UHF (2-69) antenna is required to ensure that you will receive all available television broadcasts. Low-power television is still allowed to broadcast on Low-VHF everywhere in North America. If these broadcasts are of interest to you, then you need a VHF-UHF antenna. If the antenna that you purchased 20 years ago is free of corrosion and broken elements, then it will work as well as the newest antennas from vendors making outlandish claims.
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Old 7-Dec-2011, 12:54 AM   #5
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Reception

Even as far back as the late 1930's , early 1940's , at the very beginnings of all electronic tv transmission and reception , analog high definition pictures of 1000 lines was possible and was demonstrated. And there were no so called HD antennas then.

Last edited by Electron; 20-Oct-2012 at 3:05 PM.
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Old 7-Dec-2011, 1:29 AM   #6
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Reception

Here is the truth about tv channels 2 thru 6. The VHF Low Band Tv channels of 2 thru 6 are not going away any time soon. Here is the real and actual FCC , Federal Communication Commission web site , http://transition.fcc.gov/fcc-bin/tv...&slon2=&size=9 . VHF Low Band tv channels of 2 thru 6 are being transmitted here in the USA and are still being transmitted in Canada and Mexico. It is interesting that miss information gets spread , even among those that know what they are talking about. I do not know every thing , however I do more research , way more research then most people. I am looking to get as close to the truth as possible and if I land right on the truth , then all the better for me.

Last edited by Electron; 7-Dec-2011 at 7:13 AM.
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Old 7-Dec-2011, 4:29 AM   #7
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There actually is one design parameter that is more important now than in the analog days - VSWR, or the impedance match between the antenna and feed line. Digital television tuners work best when the VSWR is low and stable across the 6 MHz channel. Most antenna designs from the analog days still work just fine, though.
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Old 7-Dec-2011, 4:40 AM   #8
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Here are some tables that summarize the use of the various bands.

This is the table you were trying to link.

Last edited by mtownsend; 7-Dec-2011 at 6:13 AM. Reason: Edited to remove off-topic comments
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Old 7-Dec-2011, 6:02 AM   #9
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Vswr

The VSWR Voltage Standing Wave Ratio of tv antennas of many years ago and current tv antennas are and have been designed to receive tv transmissions with no problems. Has to be that way , or the antenna will not sell , after being on the market for a short time.
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Old 7-Dec-2011, 6:48 AM   #10
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Actually, there are long-sellng models that have less than ideal VSWR performance, especially at the low end of the UHF band. The models we normally recommend don't suffer from this problem.
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Old 7-Dec-2011, 5:44 PM   #11
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Going back to the original poster's question...

Our owner tells of how, back when he started the company, he'd ship antennas out appropriately marked as UHF or VHF antennas. Purchasers would send them back for a refund because they "specifically wanted an HD antenna". As he relates, he finally just said with a sigh, "Fine, it's an HD antenna..." and those returns stopped.
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Old 7-Dec-2011, 7:29 PM   #12
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@ ADTech, This reminds me of a similar reaction by broadcast customers when I worked for a Telco in the 1980's. Until then, we had provided broadcast quality circuits to television stations and networks using microwave and toll-grade copper cable. As fiber-optic technology arrived in the field, we often heard the customer request a 'fiber link'. (After all, newer is always better. Right?) The tariffs defined the performance requirements of the circuit, but not the technology used to provide the service.

The Grass Valley brand single channel fiber hardware used analog modulation of an FM carrier. The laser light source was switched on and off at the frequency of the FM carrier. Even when short-hall analog facilities on copper or microwave had better frequency response, lower noise and lower distortion, some customers would insist on fiber, thinking it was digital.

As you say, "the customer is always right"... no matter how wrong they are.
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Old 9-Dec-2011, 6:31 AM   #13
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3dB loss from 2:1 SWR

I know the actual lose from a swr of 2 is only 0.5 dB but the digital signal is more
fragile to the effects of high swr than old analog signals were, due to error
vector magnitude high swr can render a signal unwatchable.
And even moderate swr of 2 can raise the "effective noise factor" by at least 3 dB
with regard to a digital signal.

That's half the signal or twice the noise depending on how you look at it.
So well designed /engineered antennas work the same as they ever did.
Also old antennas (and some new but old design) may be designed to peak at
channels above what are now used.

All you uber-gurus out there.
If any one can show how to calculate this effective increase in noise
factor for any given swr It would be greatly appreciated

Last edited by ghz24; 9-Dec-2011 at 7:50 PM.
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Old 19-Oct-2012, 2:20 AM   #14
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Thanks to all!

Thanks to all ... .this is the same brother in law who said the moon cannot come out in the daytime.
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Old 20-Oct-2012, 3:56 AM   #15
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jeffj318 . Thanks for reposting this thread , it has to the point information about the , so called HD antennas.
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Old 22-Oct-2012, 5:41 PM   #16
elmo
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Originally Posted by jeffj318 View Post
Thanks to all ... .this is the same brother in law who said the moon cannot come out in the daytime.
LOL! You my sir are obviously in the midst of pure genius!
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Old 25-Oct-2012, 2:58 AM   #17
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Originally Posted by ghz24 View Post
All you uber-gurus out there.
If any one can show how to calculate this effective increase in noise factor for any given swr It would be greatly appreciated
I don't know any way to calculate it. My approach would be to introduce a high SWR line between the antenna and the tuner; like a 75 ohm line (with choke balun) between a 300 ohm antenna and the tuner for a 4:1 SWR. Then I would measure the signal dropout point, with an attenuator and a signal level meter, and note its difference in dB from the 1:1 condition, which should indicate the amount of deterioration of NF. The EVM theory says that this deterioration is more than what would be accounted for by the increased line loss because of a higher SWR.

holl_ands has a few things to say about EVM:

Quote:
High...and even moderate SWR can distort the digital ATSC waveform, as signals mimic multipath bouncing up and down the coax downlead (Preamp's not so much).
EVM (Error Vector Magnitude) is a measurement of the amount of distortion:
http://www.digitalhome.ca/forum/show...&postcount=716

Technically speaking, the digital decision "eye pattern" becomes very noisy, as the 8 VSB amplitude levels become very indistinct, since the SWR reflections are mis-aligned in time to the primary signal. Dr. O Bendov describes this as so many dB of Noise Figure degradation, which is somewhat of a misnomer....

Bear in mind that, in a perfect world, ATSC needs more than 15 dB SNR if the Noise is truly Random, which corresponds to an SWR of about 1.4.
Fortunately the "multipath" bouncing up and down the coax isn't Random, and the Tuner isn't affected until seeing the TWICE reflected signal (down, up and back down), which is about 7.5 dB each way or SWR of about 2.5.
So ATSC actually tolerates a significantly higher SWR....I try for under 2.7.
In the link to post 716 by holl_ands, he seems to think there is some justification for calling an antenna an HD antenna if it has a low SWR:
Quote:
So indeed there IS a difference between Analog & DTV antennas....
DTV Antennas also need very good SWR performance.....
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Last edited by rabbit73; 25-Oct-2012 at 11:22 PM.
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