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Old 11-May-2010, 4:44 PM   #1
otadtvman
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7 to 51 or 14 to 51 Antennas?

Hello Everyone

Since the DTV transition, UHF channels in the US end with channel 51. However, almost a year later, most antennas available are still designed to receive through channel 69. I understand that by rescaling antennas to 51, their gain performance can be improved.

Is there a current list of rescaled antennas? I would be especially interested in models designed for fringe reception?

Thanks
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Old 11-May-2010, 6:14 PM   #2
ADTech
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Of the major antenna manufacturers, only Antennas Direct has brought products to market optimized for the truncated UHF band. These would be the ClearStream Micron, ClearStream C1, ClearStream C2, and ClearStream C4 which are all optimized for the post-transition U.S. UHF band.

The ClearStream C5, which is derived from the C1, is available as a separate add-on unit for VHF 7-13 for areas that need high-VHF performance in addition to UHF reception.

There are several hobbyist-created antennas, well discussed at the Digital Home Canada website, that are available as DIY projects for UHF that have been re-scaled.

To date, I am unaware of any 7-51 combo antennas that may be on the market. As manufacturers who sell into Canada will tell you, it is still premature to abandon UHF performance up to channel 69 as Canada still has more than a year remaining before their UHF spectrum is reduced.

Please keep in mind that rescaling an existing 14-69 UHF antenna to cover 14-51 more effectively will cause the antenna to grow by about 20% for similar performance. As many legacy UHF designs peak strongly at the high end of the UHF band (700 MHz or more), the re-scaling moves the gain curve lower in the UHF band and the narrowed bandwidth allows for greater efficiencies.

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Last edited by ADTech; 11-May-2010 at 6:26 PM.
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Old 12-May-2010, 9:54 PM   #3
otadtvman
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Hi ADTech,

Thanks for the reply.
Quote:
Originally Posted by ADTech View Post
To date, I am unaware of any 7-51 combo antennas that may be on the market.
A Google shopping search does provide results for "7 to 51 antennas". However, I suspect that some of these models may actually be 7 to 69 antennas that are being advertised as "7 to 51".

Quote:
Originally Posted by ADTech View Post
Please keep in mind that rescaling an existing 14-69 UHF antenna to cover 14-51 more effectively will cause the antenna to grow by about 20% for similar performance. As many legacy UHF designs peak strongly at the high end of the UHF band (700 MHz or more), the re-scaling moves the gain curve lower in the UHF band and the narrowed bandwidth allows for greater efficiencies.
I understand that a yagi will peak strongly at the high end of the UHF band:

01-18-08
Quote:
Originally Posted by ghostie View Post
But I then go to this page and notice that they don't recommend yagi antenna's because of the cutover:
"Note also that now is not a good time to buy a Yagi antenna. Present Yagi antennas are optimized for channel 69. But beginning on 2/17/09, 51 will be the highest channel, and a new generation of Yagi antennas cut for channel 51 will be the most desirable. For the next few years Yagi buyers must pay close attention to the frequency specs."
- http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

Why is this an issue? Sure, channel 52-69 won't be utilized, but is there anything wrong with a standard channel 2-69 yagi antenna after the cutover?
01-18-08
Quote:
Originally Posted by HDTVChallenged View Post
In the real world, it's probably not a big issue. If the antenna works ok now, it's not going to suddenly crap out when chs 53-69 go way.

OTOH, a pure UHF yagi is designed so that the are most sensitive at the highest frequency (Ch69 currently), the sensitivity decreases (sometimes dramatically) as the frequency decreases. Most real world "yagi" designs include a rear reflector that helps offset the loss at lower frequencies. A lower tuning frequency will result in less gain "loss" at ch14 and perhaps a slightly better gain at ch51.

Edit:

Why tune to the highest frequency you ask? Because the antenna gain rapidly drops to zero dB or less above the tuning frequency.
However, why does rescaling for 14-51 cause the antenna to become ~20% larger.

Thanks
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Last edited by otadtvman; 19-May-2010 at 4:54 PM.
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Old 13-May-2010, 9:31 PM   #4
ADTech
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Quote:
Google shopping search for "7 to 51 antennas"
However, I suspect that some of these models may actually be 7 to 69 antennas that are being advertised as "7 to 51".
Your suspicion is correct since CM has not rescaled their antennas.

Quote:
However, why does rescaling for 14-51 cause the antenna to become ~20% larger.
In general, rescaling moves the peak of performance down-frequency from the old peak frequencies. The lower frequencies require elements that are physically longer to be resonant in the narrower design performance band. The higher frequencies, which now no longer need to be supported, were what necessitated the smaller elements and what usually cause the rapid peaking of gain at the high end of the scale. The narrower bandwidth also allows a more efficient design as demonstrated by the ClearStream product line.
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Old 13-May-2010, 10:57 PM   #5
otadtvman
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Rescaled 91XG

ADTech,

Thanks for your explanation.

91XG Antenna - "Our most powerful uni-directional UHF antenna."
  • "Wideband coverage of UHF channels 14-69"
  • Dimensions 22" H x 20" W x 93" (7.75') Deep
-----------------------------------------------
  • Rescaled for coverage of UHF channels 14-51
  • Approx. dimensions (increased by 20%): 26.4" H x 24" W x 111.6" (9.3') Deep

For those on the fringe of DTV UHF reception, especially where multi-path interference may be also be an issue, a rescaled 91XG would be greatly appreciated. The digital "cliff effect" is annoying. While it would be larger (~1.5' longer), it would still be a manageable size compared with the all-in-one combination VHF / UHF yagi antennas.
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Old 17-May-2010, 10:23 PM   #6
otadtvman
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Quote:
Originally Posted by ADTech View Post
Of the major antenna manufacturers, only Antennas Direct has brought products to market optimized for the truncated UHF band. These would be the ClearStream Micron, ClearStream C1, ClearStream C2, and ClearStream C4 which are all optimized for the post-transition U.S. UHF band.

As manufacturers who sell into Canada will tell you, it is still premature to abandon UHF performance up to channel 69 as Canada still has more than a year remaining before their UHF spectrum is reduced.

Antennas Direct Tech Support
Dear ADTech,

It is certainly to AD's credit that AD has optimized the C1, C2, & C4 for the truncated UHF band.

Since Canada is also planning to reduce their UHF spectrum, Canadians will probably defer elective antenna purchases until after their RF transition. Why invest in a new antenna now when their UHF frequencies will changing in about a year?

However, in the US, the transition has already occurred. There is no need to defer antenna purchases - its quite the opposite. Why would Americans want to invest in pre-transition-designed deep fringe antennas nearly a year after the DTV transition?

Additionally, the US population of 309 Million is obviously a much larger market than the 32 Million Canadians.

When will we Americans see the 91XG optimized for 14-51?

Thanks
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Old 18-May-2010, 2:23 AM   #7
Dave Loudin
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Information on bowtie arrays optimized for different situations can be found here. Robust discussions on commercial and home brew designs can be found here and here.
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Old 18-May-2010, 6:23 AM   #8
otadtvman
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Hi Dave,

Thanks for the links for do-it-yourself antennas. However, I'm not looking to experiment with antennas.

I'd prefer to purchase a proven 14-51 UHF antenna:
  • Top-performer for 40+ miles and double-edge-diffraction
  • Solution for multipath interference
  • Rotor friendly / low windload
  • Top-quality materials & construction
  • Reliable, able to stand the test of time and extreme weather conditions
Any suggestions?

Thanks!
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Old 18-May-2010, 2:25 PM   #9
LovesTheOTA
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As a Canadian living north of Toronto I too would great appreciate a 14-51 rescaled antenna for picking up my hard to reach Buffalo stations. Its a Canadian tradition pulling in U.S. signal leakage over the border.
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Old 18-May-2010, 2:48 PM   #10
ADTech
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Quote:
When will we Americans see the 91XG optimized for 14-51?
Disclaimer: I'm in tech support, not marketing or management. Therefore, make of this what you will...

The short answer is "When it makes financial sense to develop one and bring it to market."

Explanation:

While we'd all like to see the biggest, baddest performing antenna, the reality of this business is that a company must invest its resources where it will be expected to earn a return. The 91XG is an extremely low volume niche item sold mostly to distributors at very low margins. Given the tens of thousands of dollars in R&D costs that it takes to develop a new commercial antenna for market, all I can say is that this project is not yet high on the priority list (which has other, more important projects on it). Additionally, there is ample inventory in our warehouse to last into next year.

If and when it should become available, it will be listed on our website first.

Quote:
I'd prefer to purchase a proven 14-51 UHF antenna:
C4. Its better efficiency often makes the difference over raw gain, especially at the low end of the UHF scale. I've used it to pull in stations at the lower end of the range that a 91XG couldn't. Above channels 25-30, the 91XG or the DB8 will outperform since they're peaked at the high end.

Last edited by ADTech; 18-May-2010 at 2:56 PM.
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Old 18-May-2010, 3:45 PM   #11
Dave Loudin
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Quote:
Originally Posted by otadtvman View Post
Hi Dave,

Thanks for the links for do-it-yourself antennas. However, I'm not looking to experiment with antennas.

With all due respect, the site about bowtie arrays documents designs that have been proven through modeling and use by a host of people. You can buy kits through that site that you can easily assemble and get the performance you are looking for. Additionally, in the Digital Home forums, there is an OTA antenna chart that provides recommendation for a wide variety of situations. These recommendations are based on the discussions and experince of the forum members.

My recommendations: 1) order the bow-tie kit that matches your needs, or 2) look over the recommendations given in the referenced chart and buy one that meets up with your requirements.
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Old 19-May-2010, 1:26 PM   #12
otadtvman
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Quote:
Originally Posted by LovesTheOTA View Post
As a Canadian living north of Toronto I too would great appreciate a 14-51 rescaled antenna for picking up my hard to reach Buffalo stations. Its a Canadian tradition pulling in U.S. signal leakage over the border.
I suspect many other Canadians may also take part in the US TV reception tradition:
Quote:
About four-fifths of Canada's population lives within 150 kilometres (93 mi) of the United States border.
http://en.wikipedia.org/wiki/Canada
http://en.wikipedia.org/wiki/Canada#cite_note-152
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Old 19-May-2010, 1:53 PM   #13
otadtvman
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Quote:
Originally Posted by ADTech View Post
The 91XG is an extremely low volume niche item ...
I'm surprised especially since:
  • UHF signals do not travel as far as VHF given the same transmitter power
  • The majority of DTV stations are now UHF
  • OTA provides free HDTV for which cable providers charge a premium

Quote:
Originally Posted by ADTech View Post
If and when it should become available, it will be listed on our website first.
I would be happy to purchase a 14-51 91XG directly from AD's website.

Quote:
Originally Posted by ADTech View Post
C4. Its better efficiency often makes the difference over raw gain, especially at the low end of the UHF scale. I've used it to pull in stations at the lower end of the range that a 91XG couldn't. Above channels 25-30, the 91XG or the DB8 will outperform since they're peaked at the high end.
1.) Aren't yagi-type antennas like the 91XG recommended over bowtie type arrays in areas with multipath issues?

2.) Which has less windload?
  • a vertically-oriented antenna such as a C4 or DB8
  • a horizontally-oriented yagi antenna such as the 91XG

3.) Which antenna type is recommended for double-edge-diffraction reception areas?

Thanks
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Last edited by otadtvman; 19-May-2010 at 2:02 PM.
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Old 19-May-2010, 2:21 PM   #14
otadtvman
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Quote:
Originally Posted by Dave Loudin View Post
...in the Digital Home forums, there is an OTA antenna chart that provides recommendation for a wide variety of situations. These recommendations are based on the discussions and experince of the forum members.
Dave,

Thanks for the suggestions.

I checked the chart and it does not list any recommendations for a 14-51 UHF antenna - it only lists 14-69 antennas.

For 7-51 combo antennas the chart recommends the HD-769xP models. However, these antennas are for channels 7-69 hence their nomenclature - "HD-769xP".

Is there a UHF bow-tie kit that's recommend for 40+ miles in a double-edge-diffraction reception area?

Thanks again
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Old 20-May-2010, 12:32 AM   #15
Dave Loudin
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The bowtie kits are optimized for the 7-51 channel range, emphasizing different parts of the bands. Go to the site I linked to and read up on it. If the gains match up to what the TVFool NM figures suggest is needed, then you will be fine. If you need double-digit gain at VHF, then this is not an all-in-one solution.

Please ease up on the 7-69 vice 7-51. The people behind the antenna chart know full well what they are talking about. In their judgment, the HD-769x series is the best solution for 7-51. So what if it has gain up to 69? If it has enough gain at 14, then you're OK.
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Old 21-May-2010, 1:07 AM   #16
teleview
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Lightbulb Tv reception

When the UHF channels 70 thru 83 went away it took the manufactures awhile to rescale to 14 thru 69. Manufactures are waiting to see what will happen with the VHF high and low bands. You are making a mountain out of a french fry. You can do the cut to channel and stack em. . . . . . http://www.go2mhz.com/specimages/Wade/Taco%20uhf%20CATV%20and%20MATV%20Antennas.pdf http://www.go2mhz.com . . http://www.wade-antenna.com . . . . Or you could strap on the PB-82-BB . http://www.go2mhz.com/specimages/Wade/D1338-BB.pdf . Or you could even do this . http://www.wade-antenna.com/Wade/CircularHelical.htm . . . . http://forum.tvfool.com/showthread.php?t=410

Last edited by teleview; 21-May-2010 at 3:47 AM. Reason: Spelling corrections and update/clarify information.
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Old 21-May-2010, 6:01 AM   #17
teleview
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Lightbulb Tv reception

Ok a check of the Winegard HD9095P shows that the gain of CH 14 is 14.2 , CH 32 is 16 , CH 50 is 15.5 , CH 69 is 12.2 . . The center frequency between 14 and 51 is 32 and 33 , are you happy now?
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