The Official AVS Antenna and Related Hardware Topic! - Page 603 - AVS Forum | Home Theater Discussions And Reviews
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post #18061 of 18073 Old 02-14-2020, 01:17 PM
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Quote:
Originally Posted by lifespeed View Post
As far as I know, the best antenna tuned for our band is sold in the UK, although it is possible to arrange reasonable shipping. It is called the XB16A.
The XB16A looks good for our 14-36 UHF Band. Note the gain is given in dBd; add 2.15 to convert to dBi:



For comparison:





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If you can not measure it, you can not improve it.
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www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 02-14-2020 at 08:38 PM.
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post #18062 of 18073 Old 02-14-2020, 01:46 PM
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Originally Posted by bobchase View Post
Where did you get it? I bought a CM-3201 off of Amazon that said it was sold by Channel Master but received the old version.
I recently ordered directly from Channel Master and also received the old version despite the picture on their website showing the new one. They are sending me another one with a prepaid envelope to send the old one back. Apparently, they have both versions so anyone else ordering may want to check first with them before placing an order to get the exact version you want.
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post #18063 of 18073 Old 02-14-2020, 01:50 PM
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Originally Posted by rabbit73 View Post
I'm not surprised that Amazon did that to you; it's so typical of them. They want to sell the old stock first.

This reminds me of a similar problem that CM created with the 7777 preamp. They redesigned the 7777 so that it had only one antenna input instead of two, but kept the SAME model number. So then we have had to ask a poster with a reception problem: "Which 7777 do you have?"

Primestar31 said the new filter was available. I looked at the CM website, but wasn't certain about the specs. CM support sent the spec sheet to me by eMail and I ordered the new filter directly from CM:
https://www.channelmaster.com/TV_Ant..._p/cm-3201.htm

Amazon still shows the old filter today:
https://www.amazon.com/Channel-Maste.../dp/B01JGSC5AO



I don't think it was an Amazon issue since it says on their website: "Ships from and sold by Channel Master."
The picture does show the old version but since the new one is on the Channel Master site and some reviews indicate the new version, you might imply that they would send that one.

If it said that Amazon sold it or fulfilled the order, then it would be Amazon's fault. I ordered directly from Channel Master and received the old version (see previous post)!
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post #18064 of 18073 Old 02-14-2020, 02:09 PM
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Quote:
Originally Posted by rabbit73 View Post
The XB16A looks good for our 14-36 UHF Band. Note the gain is given in dBd; add 2.15 to convert to dBi:
For comparison:

Good plots, thanks. While the DB8e may appear superior to the XB16A just looking at the numbers, these charts don't show directivity. A Yagi antenna has better directivity than a bow tie, so if you have multi-path like we do in the bay area there is a real possibility the bow tie style antennae will perform worse. I had to repurpose my DB4e from San Francisco stations to the closer Fremont stations, as my South San Jose location had too much multipath for the bow tie.
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91XG Yagi for San Francisco, DB4e bowtie for Fremont
SiliconDust HDHR4-2US network tuners, one per antenna
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post #18065 of 18073 Old 02-14-2020, 02:09 PM
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Quote:
Originally Posted by MSZ 007 View Post
Here's an update on my quest for free HDTV. I got the 91XG set up with a CM7777v3 preamp and the results are very much improved. The best signals I've received so far have been with KNSD and KSWB. SNR has been in the mid to upper 20's for both stations. I've also noticed the signals are best once the sun goes down. They will however occasionally go from a really strong signal (SNR 28) to nothing at all about 3-4 times an hour. Also during the local news broadcasts in the evening the signals fluctuate quite a bit. For me day time and evening reception has to improve in order to justify keeping the antenna up. I'll keep trying though!

Right now I found the best location for my antenna to be the southeast corner of my house. The mast is currently set at about 17' high. See attached map.
Thank you for making the tests and posting the report. I had hoped that the reception would have shown more improvement and am surprised that reception is better on the south side. I guess it's too much to expect reliable reception with terrain in the signal path and temperature inversions.




If you can not measure it, you can not improve it.
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www.megalithia.com/elect/aerialsite/dttpoorman.html

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post #18066 of 18073 Old 02-14-2020, 02:28 PM
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Originally Posted by jkeldo View Post
I recently ordered directly from Channel Master and also received the old version despite the picture on their website showing the new one. They are sending me another one with a prepaid envelope to send the old one back. Apparently, they have both versions so anyone else ordering may want to check first with them before placing an order to get the exact version you want.
Thank you for the report.

Using the same model number for both versions is really a bad idea. I had hoped they would have learned that with the 7777 preamps.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
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post #18067 of 18073 Old 02-14-2020, 02:43 PM
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Originally Posted by rabbit73 View Post
Thank you for the report.

Using the same model number for both versions is really a bad idea. I had hoped they would have learned that with the 7777 preamps.
You would think they would change the model numbers. I'm still waiting for the second one to arrive.
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post #18068 of 18073 Old 02-14-2020, 04:51 PM
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Yeah, using the same model number causes a lot of confusion.
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post #18069 of 18073 Old 02-14-2020, 05:46 PM
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Originally Posted by labjr View Post
Yeah, using the same model number causes a lot of confusion.
Might be intentional in order to keep selling old stock.
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post #18070 of 18073 Old 02-14-2020, 10:27 PM
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Originally Posted by nathill View Post
Might be intentional in order to keep selling old stock.

Which I'm glad for! I was afraid I was getting the new 600 MHz filter from Amazon from CM after seeing @rabbit73 's post. Whew! I either got lucky or the amazon link I clicked on was specific for 700 Mhz cutoff filter. I got that link from @mattdp 's guide. Yeah I do wish they had added an extra set of numbers to their model numbers to differentiate.


https://www.amazon.com/Channel-Maste...language=en_US

-Dave

Last edited by DavidES; 02-14-2020 at 10:33 PM.
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post #18071 of 18073 Old 02-15-2020, 11:36 AM
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Quote:
Originally Posted by rabbit73 View Post
Thank you for making the tests and posting the report. I had hoped that the reception would have shown more improvement and am surprised that reception is better on the south side. I guess it's too much to expect reliable reception with terrain in the signal path and temperature inversions.
Rabbit -

I have not given up just yet and will keep trying different locations on both north and south sides. Based on my signal strength fluctuations, is that consistent with multi-path issues? Or is it something else? The fluctuations happen on all channels. Signal strength will be great for about 5-10 minutes and then drop out completely for a few seconds to a minute at a time. I can make a video of what I'm seeing if you'd like.

As far as mounting to the south side, it was just an easier installation. There aren't any obstructions in the SE corner. No tall trees or buildings in the distance. I also didn't have to go as high since I don't have to clear the peak of my roof. The mast is at 18' on that side. The two story house two doors down to the south is also not in play since its roof ridge is about the same height as the house directly next to me. Do you think going a little higher would help though?
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post #18072 of 18073 Old 02-15-2020, 04:49 PM
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Quote:
Originally Posted by MSZ 007 View Post
Rabbit -

I have not given up just yet and will keep trying different locations on both north and south sides. Based on my signal strength fluctuations, is that consistent with multi-path issues? Or is it something else? The fluctuations happen on all channels. Signal strength will be great for about 5-10 minutes and then drop out completely for a few seconds to a minute at a time. I can make a video of what I'm seeing if you'd like.

As far as mounting to the south side, it was just an easier installation. There aren't any obstructions in the SE corner. No tall trees or buildings in the distance. I also didn't have to go as high since I don't have to clear the peak of my roof. The mast is at 18' on that side. The two story house two doors down to the south is also not in play since its roof ridge is about the same height as the house directly next to me. Do you think going a little higher would help though?
I wonder if you are getting LTE interference as that issue has been discussed here recently. I would start with the following post and go down a few more posts for more information:

https://www.avsforum.com/forum/25-hd...l#post59183000
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post #18073 of 18073 Old 02-15-2020, 08:27 PM
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Tropospheric Propagation

Quote:
Originally Posted by MSZ 007 View Post
I have not given up just yet and will keep trying different locations on both north and south sides. Based on my signal strength fluctuations, is that consistent with multi-path issues? Or is it something else? The fluctuations happen on all channels. Signal strength will be great for about 5-10 minutes and then drop out completely for a few seconds to a minute at a time. I can make a video of what I'm seeing if you'd like.
A video might be interesting if you have the time.

There are several factors causing the fluctuations. Your signals are not direct LOS because of terrain interference; they are scattered which causes multipath. But most important, they are Tropo signals, which means they would go off into space and never reach you were it not for Tropospheric Propagation which creates a duct that carries them to your location.

Quote:
The best signals I've received so far have been with KNSD and KSWB. SNR has been in the mid to upper 20's for both stations. I've also noticed the signals are best once the sun goes down. They will however occasionally go from a really strong signal (SNR 28) to nothing at all about 3-4 times an hour. Also during the local news broadcasts in the evening the signals fluctuate quite a bit. For me day time and evening reception has to improve in order to justify keeping the antenna up. I'll keep trying though!
The formation of a duct is dependent upon weather conditions, primarily a temperature inversion, which varies according to a 24-hour cycle. I suggest you look at the video by Gordon West about Tropospheric Propagation. It's about ham radio signals making it all the way from Hawaii to California, but the signals are on frequencies similar to TV signals.
Gordon West Explains Tropospheric Ducting



The formation of the ducts is explained beginning at about 22:02 in the video.


see also:

Tropospheric DX Modes
http://www.dxinfocentre.com/propagation/tr-modes.htm
Most likely: 3) TROPOSPHERIC SUPER-REFRACTION (TrE), in your case

http://www.mike-willis.com/Tutorial/refraction.htm
Anomalous Propagation
Figure 7 - Surface and Elevated Ducts

The optical equivalent is a mirage:
https://www.abc57.com/news/skyline-s...ichigan-mirage

https://en.wikipedia.org/wiki/Mirage
Superior mirage

Quote:
As far as mounting to the south side, it was just an easier installation. There aren't any obstructions in the SE corner. No tall trees or buildings in the distance. I also didn't have to go as high since I don't have to clear the peak of my roof. The mast is at 18' on that side. The two story house two doors down to the south is also not in play since its roof ridge is about the same height as the house directly next to me. Do you think going a little higher would help though?
The general rule is higher is better, but because of layering, there will be hot and cold spots as you move up and down as I showed you earlier. You just have to try it.

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If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

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