The Official AVS Antenna and Related Hardware Topic! - Page 557 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 57Likes
Reply
Thread Tools
post #16681 of 16687 Unread 04-14-2017, 07:53 AM
Member
 
tripelo's Avatar
 
Join Date: Aug 2009
Location: Dallas, TX
Posts: 88
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Liked: 12
8VSB - Ostensible Echo Enhanced Tuner Sensitivity

Quote:
Originally Posted by holl_ands View Post
… In 2002 thru 2005, CRC [Communications Research Center, Canada] tested (4th Gen) Linx/Micronas, (5th Gen) Zenith and (5th Gen) Samsung PROTOTYPE ATSC Tuners, where the Multipath Test Results using BRAZIL-A thru E are provided below…
The sensitivity was tested in the presence of various power levels of the Ensembles (echos).

Quote:
… I have added a RED Column enumerating the MULTIPATH COMBINING GAIN for those test conditions that did NOT require HIGHER SNR's in order to successfully decode the Test Condition. Up to 2.5 dB of Multipath Combining Gain was provided in some cases. [Up to 3.0 dB "should" be possible with two EQUAL Strength Multipath Signals.] …
The five Images below were extracted from Holl_ands earlier post referenced above. According to Holl_ands they were extracted from the CRC document above.





Quote:
Originally Posted by holl_ands View Post
Three CRC Prototype ATSC Tuner Test Reports still showed up to 2.5 dB of MULTIPATH COMBINING GAIN.

An echo is a repeat of the original signal delayed or advanced in time. This is only slightly different than a ground reflection. It is well known that ground reflections can provide gain (sometimes combined with antenna gain, up to 6 dB or more).

The reflector an antenna also provides such an example.

It is not unreasonable to expect that laboratory conditions can exist such that the phase relationship of an echo will add and increase signal strength at an antenna, or before tuner input.

The extra signal (echo) does not have to be in perfect phase with the desired, several degrees out of phase can still result in additional signal gain (although less than maximum obtainable).

From analysis (available on request) of the data holl_ands provided, with high probability:

Four or more ensemble and multipath delay combinations contain signal energy that is in phase with the carrier such that, when combined with the carrier, they add to the carrier power, even before the signal processing/tuner.

Again, this in-phase combination is similar to the result one could get from a reflection off an antenna element (reflector), or a ground bounce reflection.


-------------------------------------------------------------------------------------


A team reporting to the NAB and FCC commented on the unusual sensitivity in this report.







Quote:
Originally Posted by NAB FCC Report above
CIN values are less than the white Gaussian noise threshold value. This is due to the definition used at CRC for describing the multipath…

Quote:
Originally Posted by holl_ands View Post
…this TIME DIVERSITY Combining Gain is very rarely MEASURED....
Quote:
Originally Posted by holl_ands View Post
…I STILL can't find a Weblink...

.
Attached Thumbnails
Click image for larger version

Name:	CRC Performance vs Ensemble (CRC Paper).jpg
Views:	146
Size:	138.9 KB
ID:	2083657   Click image for larger version

Name:	FCC CRC Comment.jpg
Views:	142
Size:	26.8 KB
ID:	2083665  
tripelo is online now  
Sponsored Links
Advertisement
 
post #16682 of 16687 Unread Yesterday, 01:14 PM
AVS Forum Special Member
 
JHBrandt's Avatar
 
Join Date: Apr 2008
Location: S. Garland, TX
Posts: 4,580
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1594 Post(s)
Liked: 779
Quote:
Originally Posted by ctdish View Post
I have seen stations as far away as Virginia Beach but skip is mostly a PIA. It will not likely get better after the repack.
John
I don't mean to hijack the thread but I'm curious, and this thread seems the most appropriate place to ask: has their been any discussion about rescaling or otherwise redesigning UHF antennas to optimize them for RF 14-36? Would it even be worth doing, either to improve gain within the TV band or to reduce gain in the soon-to-be LTE band? (Although I suppose a filter would be the most effective approach for the latter.)
JHBrandt is offline  
post #16683 of 16687 Unread Yesterday, 03:48 PM
AVS Forum Special Member
 
rabbit73's Avatar
 
Join Date: Apr 2008
Location: S.E. VA
Posts: 2,321
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 444 Post(s)
Liked: 176
Quote:
has their been any discussion about rescaling or otherwise redesigning UHF antennas to optimize them for RF 14-36?
Not that I know of, but it would make a significant difference at the low end of the UHF band.

Quote:
Would it even be worth doing
Yes, it would be worth doing as far as performance is concerned, but no US manufacturer is going to build or rescale an antenna unless they can make a profit on it.

When the UHF band was cut to 14-51, very few manufacturers rescaled. Antennas Direct rescaled a few of their antennas including the DB8 and called it the DB8e, but they didn't rescale the 91XG. The 91XG would be a winner in its class if it were rescaled for 14-36 and if there was no need for it above 36 in all areas where it would be sold.

Here is a comparison of the DB8e and the 91XG:


If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
rabbit73 is online now  
 
post #16684 of 16687 Unread Today, 07:50 AM
Advanced Member
 
ADTech's Avatar
 
Join Date: Jun 2010
Location: St Louis
Posts: 719
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 127 Post(s)
Liked: 68
Several things to note:

While the 91XG is among the favorites for a good many of folks around here, we sell so few of them compared to our other models that the expense of rescaling and retooling for it for the narrower band would probably never be recovered (which is why it wasn't done post 2009), much less make a it profitable product in the future (in my personal opinion). I have no idea what the boss is going to do regarding this, no decision has been made.

The transition is going to take at least three years in the US and longer in some areas of Canada. Any rescaled antenna sold before the year 2020 would be potentially sacrificing reception prematurely for any stations remaining active on 37-51. My suggestion is to kick back and wait for things to progress, there's plenty of time.

If anyone does want a UHF antenna that rather closely matches up with the future UHF channel band, one could always import a "Group A" Yagi antenna from the UK.
andy416us and rabbit73 like this.

Tech support for Antennas Direct
ADTech is offline  
post #16685 of 16687 Unread Today, 12:30 PM
AVS Forum Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 4,985
Mentioned: 7 Post(s)
Tagged: 1 Thread(s)
Quoted: 470 Post(s)
Liked: 194
I just completed Re-Optimization Runs for FF4 and FF6 WITHOUT Reflectors in Ch14-36 "Even Newer UHF Band" [will upload results in next few days...incl. comparison to less than Optimum simple Re-Scale]. Re-Optimizations for "Even Newer" UHF + Hi-VHF Bands are currently running [SWR isn't THAT much higher than desired range...at least in versions with NO Reflector]. FF4 [NO Refl] improved 1.1 dB on 470 MHz [9.8 to 10.9 dBi] and 1.5 dB on 608 MHz [11.2 to 12.7 dBi]....which will be in same ballpark of improvement after adding the Double Angle Reflector.

Now that I know how much BIGGER they are, the next step is to Re-Optimize AGAIN with suitably BIGGER Double Angle Reflectors, including variables for the Bowtie-To-Reflector Separation and Reflector "Bend" Angle. Last time I did these runs it took several days per Run....and I may or may not need MULTIPLE Runs per Design [also, for the Dual Band, UHF+Hi-VHF variant, I want to find the "best" WIDTH for BOTH Bands]. I don't think I'll need to try LOTS of different Reflector Heights this time....so maybe I'll be done with at least the UHF-Only version by the end of April.....

MEANWHILE, I've tried several Lo-VHF Re-Optimizations [for Ch2-6, Ch2-6+FM, Ch2-6+Ch7-13, and Ch2-6+FM+Ch7-13] for various Antenna Types [with NO Reflector to begin with], looking for something Shorter than a 2-Story House!!!!! So Far, the 2-Bay Bowtie appears to be in the lead.....and I've wasted a LOT of computer time on the Alternatives....runs are complete, so should upload Results "any day now". These tend to run in less than a day each and leave enough processor time free to run TWO at the same time on any of my 3 computers [unlike Screen Grid Reflector types that hog ALL of the 12 Hyper-Threads]. And I REALLY need to take a look at a 4th PC Tower that my [now MACBOOK] son passed on to me to see what else it needs to help heat up the back room.

I also have a Re-Optimization running for the HHH (Holl_ands Horizontal Harness) & other Mods to improve Hi-VHF for the OLD CM4228 8-Bay Bowtie, just as I did for new CM4228HD.....

Summary of Lo-VHF Designs can be found here:
Rocky Mount, VA Antenna Suggestions (Revisited)

================================================== ========
There is LOTS of Time Left to Re-Optimize a BUNCH of other Antennas....for the MOST part, Ch38-51 won't even BEGIN to move until 14Sep2018 and you'll STILL need coverage for that band for LPTV and Repeaters until the Phone Companies actually decide to BEGIN OPERATIONS....which might be early 2019...or even 2020????

Note that Phase1 is Toledo, OH [NOT incl. Detroit]....and a bunch of small DMA's:
https://www.rabbitears.info/phasemap...nel=52&phase=1

Phase 1 is scheduled to Begin Testing on 14Sep2018 and completion by 30Nov2018....for more details see my fol. post:
AVS Official Topic: The FCC and Television Spectrum Repack

FYI: My SOCAL Area [Phase 2] is scheduled to Begin Testing on 1Dec2018 and completion by 12Apr2019 and will be one of the first truly BIG DMA's to suffer an upheaval....

PS: I'm struggling trying to find a SHORT Term to describe the "Even Newer UHF Band"....cuz we've already been using "New UHF Band" to describe current Ch14-51 coverage. I'm not all that enthusiastic about "500 MHz Band" or even "Ch14-36 Band"....any suggestions?????

Last edited by holl_ands; Today at 02:19 PM.
holl_ands is online now  
post #16686 of 16687 Unread Today, 12:58 PM
AVS Forum Special Member
 
Ken.F's Avatar
 
Join Date: Jul 2010
Location: West Rockhill, PA
Posts: 4,319
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1535 Post(s)
Liked: 1329
Quote:
Originally Posted by holl_ands View Post
FYI: My SOCAL Area [Phase 2] is scheduled to Begin Testing on 1Dec2018 and completion by 30Nov2018.
Scheduled completion is the day before testing begins?

Quote:
PS: I'm struggling trying to find a SHORT Term to describe the "Even Newer UHF Band"....cuz we've already been using "New UHF Band" to describe current Ch14-51 coverage. I'm not all that enthusiastic about "500 MHz Band" or even "Ch14-36 Band"....any suggestions?????
"2019 UHF Band"?
Ken.F is offline  
post #16687 of 16687 Unread Today, 01:19 PM
AVS Forum Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 4,985
Mentioned: 7 Post(s)
Tagged: 1 Thread(s)
Quoted: 470 Post(s)
Liked: 194
Thnx for finding my Copy/Paste Error....Fixed Completion dates for both Phase 1 and Phase 2....
holl_ands is online now  
Sponsored Links
Advertisement
 
Reply HDTV Technical

Tags
Channel Master Cm 4228 8 Bay Hdtv Uhf Antenna Cm4228hd



Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off