The official final DTV Table Of Allotments/channel change thread - Page 243 - AVS Forum
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post #7261 of 7371 Old 12-07-2011, 10:15 AM
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Originally Posted by joblo View Post

No CECB that I'm aware handles QAM. I don't think that was even permitted.

Correct. FCC rules did not permit anything but 8VSB for the CECB.

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post #7262 of 7371 Old 12-07-2011, 02:29 PM
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Quote:
Originally Posted by joblo View Post

No CECB that I'm aware handles QAM. I don't think that was even permitted.

Practically.

Technically, many boxes using chips (tuner/demod) what are support QAM. Updating FW would open the feature.
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post #7263 of 7371 Old 12-07-2011, 02:34 PM
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Originally Posted by P Smith View Post

Practically.

Technically, many boxes using chips (tuner/demod) what are support QAM. Updating FW would open the feature.

I don't know how many CECB's have firmware upgrade features. Mine doesn't.

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post #7264 of 7371 Old 12-07-2011, 03:45 PM
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Quote:
Originally Posted by P Smith View Post

Practically.

Technically, many boxes using chips (tuner/demod) what are support QAM. Updating FW would open the feature.

We're talking about boxes mass marketed to J6P. "Practically" is all that counts; "technically" is irrelevant. (And resistance is futile... )
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post #7265 of 7371 Old 12-10-2011, 06:41 AM
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Okay, so somehow the FCC granted WLJC 185 kW on channel 7. Now I'm confused.

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post #7266 of 7371 Old 12-10-2011, 08:27 AM
 
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Originally Posted by Trip in VA View Post

Okay, so somehow the FCC granted WLJC 185 kW on channel 7. Now I'm confused.

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post #7267 of 7371 Old 12-10-2011, 02:52 PM
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Originally Posted by Trip in VA View Post

Okay, so somehow the FCC granted WLJC 185 kW on channel 7. Now I'm confused.

- Trip

Largest station exception, according to their technical exhibit. They claim that it takes 185 kW to match the coverage of WYMT Hazard, and apparently, the FCC agrees. Unless the FCC changes its mind in the future and rescinds the grant. Conveniently for WLJC-TV, it's just enough to put the 43 DBU contour completely over Lexington.


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post #7268 of 7371 Old 12-10-2011, 03:11 PM
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But it exceeds the 160 kW limit. They shot down KCWX's request to boost to 82 kW and WBNS's request to boost to 1700 kW on those grounds.

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post #7269 of 7371 Old 12-10-2011, 08:40 PM
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Quote:
Originally Posted by Trip in VA View Post

But it exceeds the 160 kW limit. They shot down KCWX's request to boost to 82 kW and WBNS's request to boost to 1700 kW on those grounds.

My guess (and it's only that) is that the FCC is now looking with favor on VHF. This may set a precedent in order to encourage stations to reconsider VHF over UHF.

Lookee! VHF is the hot new band! We'll give you BIG GIANT power if you give up your UHF assignment for the telecoms.
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post #7270 of 7371 Old 12-10-2011, 10:28 PM
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Quote:
Originally Posted by Trip in VA View Post

But it exceeds the 160 kW limit. They shot down KCWX's request to boost to 82 kW and WBNS's request to boost to 1700 kW on those grounds.

- Trip

KCWX didn't claim largest station exception in their application. It's also worth noting that the FCC database shows that application as still active, but ungranted. What the FCC dismissed was KCWX's STA request to begin operations at that power level prior to FCC approval of the Form 301 application, which would have to clear Mexican coordination first. I have a sense, however, KCWX has abandoned its own application, as they have now applied for a replacement DTV translator in the Austin area, to operate on RF channel 8.

While WBNS-TV did claim the largest station exception, their application admitted to 0.66% interference to co-channel WUPX Morehead KY, when calculated using Longley-Rice methodology. That's above the 0.5% permissible limit. WBNS vowed to either secure an agreement from WUPX to accept the interference, or to amend their application to lower interference to WUPX. Again, according to the FCC database, they did neither. Nor do we know if their application ever cleared Canadian coordination; I'm sure Columbus lies within the Canadian coordination zone. In any case, just based on the impermissible interference to WUPX, the FCC would dismiss that application. It would have been helpful if the FCC had published the communication with WBNS concerning this application.


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post #7271 of 7371 Old 12-10-2011, 10:29 PM
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If Low VHF could have 185,000 watts would it be suitable to use then? What is the putential coverage area for a low VHF station with that much power?

How can we say "the digital transition is complete" when thousands of low power stations are still broadcasting in analog?
LOW POWER ANALOG NEEDS TO DIE NOW!!!
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post #7272 of 7371 Old 12-10-2011, 10:55 PM
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Originally Posted by Desert Hawk View Post

If Low VHF could have 185,000 watts would it be suitable to use then? What is the putential coverage area for a low VHF station with that much power?

Wow - talk about a DXer's delight!!


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post #7273 of 7371 Old 12-11-2011, 12:04 AM
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Quote:
Originally Posted by Desert Hawk View Post

If Low VHF could have 185,000 watts would it be suitable to use then? What is the putential coverage area for a low VHF station with that much power?

I just ran a Longley-Rice estimate of how KCWX (RF-5) would look with 185 kW at its HAAT of 1351':

http://www.onairusa.com/185kw/index.html

Compare it with the present coverage with 23.7 kW at that height:

http://www.rabbitears.info/contour.p...-98.6097222222
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post #7274 of 7371 Old 12-11-2011, 02:35 AM
 
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Originally Posted by dr1394 View Post

How is 4 = 3 * 2? Increasing the bits per symbol from 3 to 4 raises the bitrate by 4/3 or 1.333. That gets us to 19.39 * 1.333 = 25.853 Mbps. Then by removing the 2/3 FEC, the bitrate is increased by 3/2 or 1.5. 25.853 * 1.5 = 38.78 Mbps. Another way to look at it is 4/3 * 3/2 = 2.

The 16-VSB numbers can be found here.

http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf

See Table 8.1

Ron

Ok if I'm reading that correctly the main differnce between 8-VSB and 16-VSB is that 8-VSB has more coding to prevent analog interference. And that extra coding is why its capped at 19 Mbps. Seeing that as of Sept 1 2015 that will not longer be an issue since all analogs will have to shut down by then then it seem that that extra coding will no longer be necessary. That would allow OTA broadcasters to use 16-VSB which means 38 Mbps. Or am I misreading that.
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post #7275 of 7371 Old 12-11-2011, 07:31 AM
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Originally Posted by BCF68 View Post

Ok if I'm reading that correctly the main differnce between 8-VSB and 16-VSB is that 8-VSB has more coding to prevent analog interference. And that extra coding is why its capped at 19 Mbps. Seeing that as of Sept 1 2015 that will not longer be an issue since all analogs will have to shut down by then then it seem that that extra coding will no longer be necessary. That would allow OTA broadcasters to use 16-VSB which means 38 Mbps. Or am I misreading that.


Possibly -
BUT -
you still need to get reception devices out to the viewers that can accept 16VSB.

You CAN put antennas on your owned and/or controlled property...

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post #7276 of 7371 Old 12-11-2011, 09:20 AM
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Originally Posted by BCF68 View Post

Ok if I'm reading that correctly the main differnce between 8-VSB and 16-VSB is that 8-VSB has more coding to prevent analog interference. And that extra coding is why its capped at 19 Mbps. Seeing that as of Sept 1 2015 that will not longer be an issue since all analogs will have to shut down by then then it seem that that extra coding will no longer be necessary. That would allow OTA broadcasters to use 16-VSB which means 38 Mbps. Or am I misreading that.

I think analog interference is the least of the issues. The error correcting also helps with multipath and noise significantly improving the useable SNR. From what I can tell, the minimum SNR for 8VSB with no error correcting is about 24 dB. Someone can correct me if I'm wrong about that. See page 9 in this PDF.

http://www.digitalproceiver.com/mods...ing%208vsb.pdf

It looks like the dots just stay within the lines at 24 dB SNR. Dots that cross the lines are errors that need to be corrected.

In Table 8.1 in the link that Ron posted above, it shows that the 8VSB symbol rate is 10.76 Msymbols/S or 32.28 Mbps. The Data Payload Rate is 19.39 Mbps. If you eliminate the Trellis coding, the Data Payload Rate should go up to 29.09 Mbps, leaving 3.19 Mbps of other overhead.

In the same table it shows 16VSB Data Payload Rate of 38.78 Mbps with no Trellis coding. If you were to add 3/4 coding for OTA use then the Payload Data Rate would go down to 29.09 Mbps.

From what I've seen, it looks like Trellis coding uses 1 bit/symbol, hence 2/3 for 8VSB and I assume 3/4 for 16VSB. There must be some SNR penalty for 3/4 compared to 2/3. 16VSB should require 3 dB higher SNR for the same performance so the transmitters need to increase power by 2X. I'm thinking that the minimum SNR for 16VSB would be on the order of 19-20 dB.

Of course this is just an exercise in "What could be done to improve efficiency?" since it would require another transition which should not happen for a long time.

Chuck


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post #7277 of 7371 Old 12-11-2011, 09:16 PM
 
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Originally Posted by Calaveras View Post

Of course this is just an exercise in "What could be done to improve efficiency?" since it would require another transition which should not happen for a long time.

Chuck

If the FCC takes away 31-51 and stations are focred to share channels it'll have to happen sooner than later.

Besides the FCC can madate that all TVs made after Jan 1st 2013 have 16VSB tuners in them. Have the transition take place in Jan 2018. That's 5 years.
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post #7278 of 7371 Old 12-12-2011, 01:12 AM
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Originally Posted by Calaveras View Post

Of course this is just an exercise in "What could be done to improve efficiency?" since it would require another transition which should not happen for a long time.

Chuck

If it was possible to have another transition, then using 16-VSB would be a pretty silly way to go. It's a 90's technology that never saw the light of day.

There have been many advances in error coding and modulation since 1995. Many of these new techniques (like Low Density Parity Check and Bose-Chaudhuri-Hocquenghem multiple error correction binary block codes) are used in the DVB-T2 specification.

From this document, it would seem that a 27 Mbps service could be obtained in a 6 MHz channel at around 16 to 17 dB signal to noise ratio. Or even more trickier, a 20 Mbps service in a 4.5 MHz channel. Then you could have the same number of TV stations delivering an ATSC similar service in 25% less RF bandwidth.

http://www.dvb.org/technology/standa..._Imp_Guide.pdf

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post #7279 of 7371 Old 12-12-2011, 04:49 AM
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No matter what KCWX does with their ERP at that "remote" TL, it will still deliver the best signal to more cattle and mesquite than to OTA viewers. The long tale of one of perhaps last full-power US commercial Ch 2 NTSCs to be licensed
http://www.qsl.net/wa5iyx/fred-2.htm
That said, my viewing them as a 23-kw DT-5 has been far superior to their 100-kw analog 2 with all the interference it would suffer (lightning, appliances, co-channel from Houston tropo and the rest of country's on Es) at 46 miles away.
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post #7280 of 7371 Old 12-13-2011, 04:07 PM
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Another transition in 2018?! Are you freaking joking?! HELL NO!!! The public should riot in the streets if that happens. Even 2028 or 2038 are way too soon for another nonbackwardcompatible transition. Something of the magnitude of what we went through last decade should be a once in a lifetime thing!

How can we say "the digital transition is complete" when thousands of low power stations are still broadcasting in analog?
LOW POWER ANALOG NEEDS TO DIE NOW!!!
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post #7281 of 7371 Old 12-13-2011, 08:19 PM
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Another transition in 2018?! Are you freaking joking?! HELL NO!!! The public should riot in the streets if that happens. Even 2028 or 2038 are way too soon for another nonbackwardcompatible transition. Something of the magnitude of what we went through last decade should be a once in a lifetime thing!

Hi,

Transition in 2018, I will not be around then perhaps but I expect the OTA to Cable / Satellite / Internet transition to be almost completed by then.

What might remain of OTA DTV at that point, look at Channel 1 (ONE). That service with 12 video channels will be the pattern for sure. (First in list)

Quote:


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Even the equipment that KAXT uses is pretty.

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HDTV, you think that it will be forever free, ROFLOL.

Remember, we had a "DTV" transition, NOT a "HDTV" transition.

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post #7282 of 7371 Old 12-13-2011, 11:43 PM
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As it turns out, the ATSC 3.0 folks have already considered using LDPC and BCH error correction codes with 8-VSB.

http://atsc.org/cms/pdf/pt2/02-PT-2-...-Yiyan-V10.pdf

On page 40, it looks like a 24 Mbps service is possible at 15 dB S/N ratio.

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post #7283 of 7371 Old 12-14-2011, 08:39 AM
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Quote:
Originally Posted by dr1394 View Post

As it turns out, the ATSC 3.0 folks have already considered using LDPC and BCH error correction codes with 8-VSB.

http://atsc.org/cms/pdf/pt2/02-PT-2-...-Yiyan-V10.pdf

On page 40, it looks like a 24 Mbps service is possible at 15 dB S/N ratio.

Ron

I'm doing my best to understand this. In another link you posted there was a table that said that the ATSC symbol rate is 10.76 Msymbols/S or 32.28 Mbps. Looking at the graph on page 40, that would correspond to a Shannon limit of about 20 dB C/N. This is what I read somewhere else as the essentially error-free C/N requirement with no error correcting.

If I understand this correctly, the Data Rate label is actually the Data Payload Rate, a term used in your other link. Data Payload Rate meaning the actual useable data which is what's left over after all overhead is accounted for; i.e., error correction and whatever else there is.

So it appears that the newer error correction schemes use fewer bits to achieve the same level of error correction as the current ATSC system does thus resulting in a greater Data Payload Rate.

Further it appears that all this error correction has been implemented to reduce the useable C/N from around 20 dB to 15 dB.

On top of greater error correction efficiency with these newer methods, there's also greater data compression efficiency that can be achieved by moving from MPEG2 to MPEG4.

Do I have this correct or have I missed something?

At the end of the presentation it is stated that OTA can never compete with satellite or cable in terms of bandwidth efficiency. I assume this is because the latter two don't need any error correcting. But it is also stated that OTA has its own advantages.

Chuck


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post #7284 of 7371 Old 12-14-2011, 09:18 AM
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Originally Posted by Calaveras View Post

At the end of the presentation it is stated that OTA can never compete with satellite or cable in terms of bandwidth efficiency. I assume this is because the latter two don't need any error correcting. But it is also stated that OTA has its own advantages.

Over the air suffers from multipath that is not present in satellite signals.

Satellite signals suffer from the extreme distances between the satellite and the ground station and the high gain antennas needed to compensate.

Bottom line, if you use the right antenna for terrestrial broadcasting it can work fine, but mistakes in antenna selection and installation are well documented in these forums. For mobile reception, a large, perfectly aimed satellite antenna is impractical, so over the air wins.

I'd suggest that few try to install their own satellite antenna, but many attempt to self-install an over the air antenna. The gap in experience can explain many of the OTA miscues.
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post #7285 of 7371 Old 12-14-2011, 06:23 PM
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Over the air suffers from multipath that is not present in satellite signals.

I'd suggest that few try to install their own satellite antenna, but many attempt to self-install an over the air antenna. The gap in experience can explain many of the OTA miscues.

I have had to find that out by trial and error. I have installed several outdoor antennas for family, friends, and coworkers. Most got beautiful results immediately while a couple were far less than ideal. I spent many hours wringing hands and pulling hair out before learning what the cause was. Short term multi-path overloading the tuner being the biggest bug-a-boo I have run into. I now know what to look for and be aware of when selecting a location to install, but those with less experience may have given it one shot, got less than desirable results, and given up...

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post #7286 of 7371 Old 12-15-2011, 02:49 AM
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Quote:
Originally Posted by Calaveras View Post

I assume this is because the latter two don't need any error correcting.

256-QAM used on US cable systems is still coded, but fairly lightly. The symbol rate for 256-QAM is 5.360537 Msps. There are 8 bits per symbol, so the raw bitrate is 42.88430 Mbps. The payload rate is 38.81070 Mbps, so there's only about 10% wasted in error correction coding. Compare that with 40% for 8-VSB, and you can see what the author was getting at.

Cable 256-QAM is described in this standard.

http://www.scte.org/documents/pdf/St...SCTE072006.pdf

Satellite is similar, although they use a little more coding. Typically a 3/4, 5/6, 6/7 or 7/8 rate FEC.

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post #7287 of 7371 Old 12-15-2011, 08:15 AM
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I have had to find that out by trial and error. I have installed several outdoor antennas for family, friends, and coworkers. ... I now know what to look for and be aware of when selecting a location to install...

Location, location, location... this has been the biggest problem for lots of folks here in the SF Bay Area. We've found that just a few feet one way or the other, either horizontally or vertically, can make a big difference in what you receive. Moving the antenna from one side of the house to the other or raising it or lowering it a few feet can solve a lot of problems.

I recently had a two man crew work on my antennas. Used to do it myself, but I'm getting too old to do it now. They installed two push-up masts and once the antennas were installed they raised and lowered them to find the best spots. I now get some distant stations up to 7 dB stronger that I used to. Same antennas, same location on the roof, just different heights... in this case it's higher in both cases.

I think a 29 dB signal on channel 32 from 65 miles away is pretty good.

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post #7288 of 7371 Old 12-15-2011, 09:32 AM
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Originally Posted by Larry Kenney View Post

Location, location, location... this has been the biggest problem for lots of folks here in the SF Bay Area. We've found that just a few feet one way or the other, either horizontally or vertically, can make a big difference in what you receive. Moving the antenna from one side of the house to the other or raising it or lowering it a few feet can solve a lot of problems.

I recently had a two man crew work on my antennas. Used to do it myself, but I'm getting too old to do it now. They installed two push-up masts and once the antennas were installed they raised and lowered them to find the best spots. I now get some distant stations up to 7 dB stronger that I used to. Same antennas, same location on the roof, just different heights... in this case it's higher in both cases.

I think a 29 dB signal on channel 32 from 65 miles away is pretty good.

Larry
SF

It is the same here. A few feet here or there can mean all the difference. We don't have hills here. It is about as flat as you can get... You would think it would ne a piece of cake. Ah, not so. It's the trees with their little year 'round sub-tropical leaves flickering in the wind. They wreak havok with multi-path...

You never know where the LIMIT is until you EXCEED it... Dianne B. "Let's try that again... without the oops." (Will Smith and Jeff Goldblum in "Independence Day")
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post #7289 of 7371 Old 12-15-2011, 03:52 PM
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Originally Posted by OTAhead View Post

It is the same here. A few feet here or there can mean all the difference. We don't have hills here. It is about as flat as you can get... You would think it would ne a piece of cake. Ah, not so. It's the trees with their little year 'round sub-tropical leaves flickering in the wind. They wreak havok with multi-path...

Hi,

We had a big windstorm here in California. I was trying to watch the noon news on two stations, RF 29 and RF 44. Both were very choppy on short time frames. This was something new that I had not see before.

I looked out my window and tall trees ~ 100 feet away were swinging like mad.

The temperature inversion over the bay and the mountain reflections are what I usually fight, RF 29 and RF 30 were gone for a while this fall, now back. That also was new. (Early rain?)

Leaves on the trees will be soon gone. I can remember ~ 1975 coming home early the day before DST ended so I could rake the last of the leaves with some light, now mid December and lots of leaves are still on.

SHF
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post #7290 of 7371 Old 12-16-2011, 11:50 AM
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tall trees ~ 100 feet away were swinging like mad.

Dynamic multi-path.

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