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Old 2-Oct-2016, 3:49 PM   #21
Blackbeen
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Quote:
Originally Posted by bobsgarage View Post
Glad to hear you tried the preamp. Was this all done with the HDB91X & 30-2476 ?

How did you combine the two antennas, with MCM combiner still ?

Also, I am assuming you are using the "real" channels numbers, not the virtual number, it appears to be the case.
Same stack to combiner to FM Filter to Preamp, yeah real channels to magnetic point, still no WMYD 20, even last night at a close to 50 channel peak where I was pulling ION & WADL-DT, I find this really bizarre.
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Old 2-Oct-2016, 5:19 PM   #22
rabbit73
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WMYD is not real channel 20, it is real channel 21 and VIRTUAL channel 20.1. If you are going to use a virtual channel number, please use the decimal form to avoid confusion. Giving the callsign, as you just did, is even better.
Quote:
I find this really bizarre.
So do I. There is a reason; we just haven't discovered it yet. They might be having transmitter trouble, or you might have interference to that channel.
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Old 2-Oct-2016, 5:38 PM   #23
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Originally Posted by rabbit73 View Post
WMYD is not real channel 20, it is real channel 21 and VIRTUAL channel 20.1. If you are going to use a virtual channel number, please use the decimal form to avoid confusion. Giving the callsign, as you just did, is even better.
In conversation I always refer to the channel number the station is identified with rather than the real (assuming its different), I understand the difference, regardless I tried the direct 20.1 point of 29 degrees magnetic this morning & I was surprised that I lost all but 6 channels of 36 (with the 22 degree point), I know its directional but that is a really an extreme blackout point, even local WNWO-TV 49 (24) dropped which I get with a 22 degree point with preamp even though its 98 degrees magnetic, anyhow WMYD is still a mystery.
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Old 2-Oct-2016, 6:18 PM   #24
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In conversation I always refer to the channel number the station is identified with rather than the real
I refer to the channel by its real channel number because

1. it is the real channel number that determines the antenna needed.
2. the real channel number is always listed on the report, but the virtual channel number isn't always listed.
3. sometimes two channels will have different real channel numbers, but the SAME virtual channel number.

Quote:
I understand the difference
You might understand the difference, but the way you state it isn't clear.

Using the callsign avoids that ambiguity and uncertainty.

Why don't you call the WMYD station engineer?
Quote:
I was surprised that I lost all but 6 channels of 36 (with the 22 degree point), I know its directional but that is a really an extreme blackout point,
This is the time of year for tropospheric propagation when you will receive channels that you will not usually receive.
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Last edited by rabbit73; 2-Oct-2016 at 6:28 PM.
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Old 2-Oct-2016, 6:35 PM   #25
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Originally Posted by rabbit73 View Post
Why don't you call the WMYD station engineer?
This is the time of year for tropospheric propagation when you will receive channels that you will not usually receive.
I might if I find the time & it nags me enough, none of the channels received in the sweet 22 degree range are highly unusual for any time of the year in this general location in the last 4 or so years of OTA usage. I find this selection to be the norm rather than the exception if not perhaps a bit lower than average from the sandwich days of DB4e with a working preamp at my old Apt a couple years ago. Improved stability for WDIV has its costs I guess.
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Old 2-Oct-2016, 6:47 PM   #26
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WDIV on real channel 45 has adjacent channel interference from WUPW on real channel 46. A tuner is not expected to reject adjacent channel interference that is more than 33 dB stronger. WUPW is 49.6 dB stronger than WDIV.

5.4.2 Adjacent Channel Rejection

The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first
adjacent-channel interference at the desired signal levels shown above the columns therein.



When you overload a tuner with local signals, it makes reception of weaker signals more difficult, because spurious signals are created in the tuner from IMD (Intermodulation Distortion) that damage the weak signals.

WUPW -29.1 dBm + 13 dB ant + 18 dB preamp = +1.9 dBm; tuner overload

ATSC Recommended Practice:
Receiver Performance Guidelines


Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity

Quote:
A DTV receiver should achieve a bit error rate in the transport stream of no worse than 3x10E-6 (i.e., the FCC Advisory Committee on Advanced Television Service, ACATS, Threshold of Visibility, TOV) for input RF signal levels directly to the tuner from –83 dBm to –5 dBm for both the VHF and UHF bands.
5.2 Multi-Signal Overload

Quote:
The DTV receiver should accommodate more than one undesired, high-level, NSTC or DTV signal at its input, received from transmission facilities that are in close proximity to one another. For purposes of this guideline, it should be assumed that multiple signals, each approaching –8 dBm, will exist at the input of the receiver.
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Last edited by rabbit73; 2-Oct-2016 at 7:22 PM.
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Old 2-Oct-2016, 7:17 PM   #27
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Sometimes the combiner you are using has problems. What happens to WMYD when you connect the UHF antenna to the tuner with and without the preamp, bypassing the combiner?

UHF Ant > FM filter > grounding block > tuner

UHF Ant > FM filter > preamp > grounding block > power inserter > tuner

Which FM filter are you using?
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Last edited by rabbit73; 2-Oct-2016 at 7:19 PM.
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Old 2-Oct-2016, 8:30 PM   #28
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Quote:
Originally Posted by rabbit73 View Post
WDIV on real channel 45 has adjacent channel interference from WUPW on real channel 46. A tuner is not expected to reject adjacent channel interference that is more than 33 dB stronger. WUPW is 49.6 dB stronger than WDIV.

5.4.2 Adjacent Channel Rejection

The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first
adjacent-channel interference at the desired signal levels shown above the columns therein.



When you overload a tuner with local signals, it makes reception of weaker signals more difficult, because spurious signals are created in the tuner from IMD (Intermodulation Distortion) that damage the weak signals.

WUPW -29.1 dBm + 13 dB ant + 18 dB preamp = +1.9 dBm; tuner overload

ATSC Recommended Practice:
Receiver Performance Guidelines


Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity



5.2 Multi-Signal Overload
In short this is why I opted for a more directional antenna to address this, there has been improvement.
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Old 2-Oct-2016, 8:38 PM   #29
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Quote:
Originally Posted by rabbit73 View Post
Sometimes the combiner you are using has problems. What happens to WMYD when you connect the UHF antenna to the tuner with and without the preamp, bypassing the combiner?

UHF Ant > FM filter > grounding block > tuner

UHF Ant > FM filter > preamp > grounding block > power inserter > tuner

Which FM filter are you using?
This crossed my mind but I would have to take down the whole stack to access the combiner & I don't have another afternoon to forfeit doing that right now, too much other house stuff to do, recabling ate a whole afernoon yesterday I had planned for other work.
The FM Filter was bought at radio shack a 3-4 years ago, not sure of the model, it resolved the issue I had with WTOL 11 breakup I had at the time.
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Old 2-Oct-2016, 10:03 PM   #30
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In short this is why I opted for a more directional antenna to address this, there has been improvement.
Good, a more directional will help that because they are in different directions.
Quote:
The FM Filter was bought at radio shack a 3-4 years ago, not sure of the model, it resolved the issue I had with WTOL 11 breakup I had at the time.
Also good.
Quote:
I don't have another afternoon to forfeit doing that right now
Understood
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Old 4-Oct-2016, 4:03 PM   #31
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It's not a factor at this point since I recabled to a separate rotor connection but a FYI to anyone who might want to attempt a single cable connection with the ROTR100 from ProBrand support: " Channel Master Spartan series Pre Amps draw less current so 0068DSB, 0268DSB are good ones and 0065DBS and 0265DSB come without the power supply so may be a cost saving as well.. I am not sure if they still have these lower voltage, lower current draw units but that is where to check."

I also contacted WMYD & they verified that there have been no changes on their end so at this point I have conclude that the loss of DB4e from the stack or the combiner are the cause, not a lot of time to verify this in the next couple weeks.
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Old 4-Oct-2016, 10:39 PM   #32
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That sounds like the same list I got from them 5 or so years ago when we were selling that rotor. Only problem is that all of those Spartan models were discontinued some 5+ years ago. That makes it a pretty tough proposition to score one unless you get lucky.
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Old 5-Oct-2016, 2:09 AM   #33
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Double rescan

Double rescan

Have you tried a double rescan? It is possible that the tuner memory has become corrupted by, for example, WHNE on real channel 20 at the same azimuth.

https://www.google.com/?gws_rd=ssl#q=fcc+double+rescan
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Last edited by rabbit73; 7-Oct-2016 at 12:29 AM.
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Old 5-Oct-2016, 5:44 PM   #34
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Quote:
at this point I have [to] conclude that the loss of DB4e from the stack or the combiner are the cause
That got me wondering about the UHF antenna change. It wouldn't be gain, so maybe it is a slight change of antenna location or the form factor of the antenna.

I did a terrain profile that shows how the curvature of the earth blocks the direct signal and causes it to graze the surface and be subjected to ground clutter interference.



The ground clutter interference will cause scattering of the signal so that it presents a non-uniform wave front to the antenna. This non-uniform field makes the location of the antenna very critical, because there will be hot spots and cold spots.







It is also possible to have a non-uniform field in the vertical direction. Moving a UHF antenna a little as 6 inches up or down can make a difference. That would be easier for you to do than moving it in a horizontal direction. I wonder how the DB4e would do now?

http://www.hdtvprimer.com/antennas/siting.html
Attached Images
File Type: jpg BlackbeenTVFp2WMYD.JPG (106.7 KB, 591 views)
File Type: jpg Non-uniform fields HDTVPRIMER snip2_1.jpg (142.5 KB, 2447 views)
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Last edited by rabbit73; 5-Oct-2016 at 6:50 PM.
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Old 5-Oct-2016, 6:59 PM   #35
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I was having trouble receiving CH 42 because my antenna was facing the wrong direction. The signal was strong enough, but the signal quality was poor; the tuner was not able to pick it up during a scan.



As you can see, the top of the signal is not very flat, which probably indicates a multipath reflection problem. That's not surprising, because the antenna is aimed in the opposite direction and only reflections off the objects in front of the antenna are picked up; there is no direct signal from the transmitter.

I went across the street and setup a 2-bay UHF antenna, my Sadelco DisplayMax 800 signal level meter, and a CM7777 (original) preamp. I was able to get a nice scan and a stronger signal with the antenna aimed at the transmitter for CH42.



Interestingly, when I moved the antenna a few feet left or right, without changing the height or azimuth, there was a big difference in the signal strength and scan quality. This is most likely because of the tree line in front of the antenna about 200 ft away which created the non-uniform field.

I was able to get a nice scan and a stronger signal with the antenna aimed at the transmitter for CH42.



My 8-inch Audiovox TV in the car was able to pick up CH42 WCVE; the 22-inch Sony was too big to bring along.

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Last edited by rabbit73; 6-Oct-2016 at 12:49 AM.
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Old 6-Oct-2016, 10:51 PM   #36
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Great explanation of multipath by Rabbit, who else?

Quote:

The ground clutter interference will cause scattering of the signal so that it presents a non-uniform wave front to the antenna. This non-uniform field makes the location of the antenna very critical,

It is also possible to have a non-uniform field in the vertical direction. Moving a UHF antenna a little as 6 inches up or down can make a difference.

http://www.hdtvprimer.com/antennas/siting.html
Rabbit,

I have to hand it to you, that was the best explanation I've ever seen of multi path. I for one didn't get it to be honest. I think I'm getting the hang of what multipath means now.

Using those illustrations sealed the deal for me. Is Ken Nist still active?
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Old 7-Oct-2016, 12:20 AM   #37
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Quote:
that was the best explanation I've ever seen of multi path.
Thank you for your kind words; I'm still learning so that I can make clear explanations.
Quote:
Using those illustrations sealed the deal for me.
I have learned a lot from Ken's website.
http://www.hdtvprimer.com/
Quote:
This web site was created in 2003 to help nontechnical people cope with the digital transition. The transition is now history, and with it much of the reason for this site.

The unique parts of the web site have been left up. The site will continue to track new developments in over-the-air TV antennas.
Quote:
This document is Copyright 2002-2009 by Ken Nist. The “document” includes all web pages at www.hdtvprimer.com. The author places no restrictions on the use of this document. It may be used by anyone in any manner for any purpose.
Quote:
Is Ken Nist still active?
His website is still up most of the time, but he doesn't add to it anymore and has only retained the essential parts. I don't know about the "active " part. His ham license is still active, and was renewed in 2013:
http://wireless2.fcc.gov/UlsApp/UlsS...?licKey=621708
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Last edited by rabbit73; 7-Oct-2016 at 12:25 AM.
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