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Old 30-Oct-2016, 2:07 AM   #1
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,518
Could you post a thread for me to get opinions on antenna?

frg34 needs antenna help and has asked me to post for him.

Quote:
Originally Posted by frg34
Doesnt seem like they are approving new members. could you post for me? thanks
Coastal Maine, lots of trees, hoping to get WCSH nbc, WGME cbs, WMTW abc and WPFO fox.
http://www.tvfool.com/?option=com_wr...dfaf1b33bbd3a3
I
He has one strong local FM transmitter that might interfere with reception of his weak TV signals received by an antenna surrounded by trees:
http://www.fmfool.com/modeling/tmp/0...2/Radar-FM.png
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Last edited by rabbit73; 30-Oct-2016 at 2:20 AM.
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Old 30-Oct-2016, 6:30 PM   #2
rabbit73
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Location: S.E. VA
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Welcome, frg34:

WCSH NBC 44, NM -14.5 dB, 57.1 mi, 263 deg
WGME CBS 38, NM -6.2 dB, 45.6 mi, 266 deg
WMTW ABC 8, NM -14.4 dB, 59.5 mi, 262 deg
WPFO Fox 23, NM +7.7 dB, 25.0 mi, 301 deg

You are in a very difficult location for TV reception. The signals are weak, they are in different directions, they are on all 3 TV bands (only 2 bands for the 4 you want), you are down the hill near the river at a lower elevation, and surrounded by trees.

It is the real channel number that determines what antenna is needed.

VHF-Low, real channels 2-6
VHF-High, real channels 7-13
UHF, real channels 14-51

Not impossible, just difficult.



I don't have your exact location, but I did a 25 ft report based on my estimate; I think I'm pretty close:
http://www.tvfool.com/?option=com_wr...dfafdf4c115309

WCSH and WMTW look a lot better at 50 feet:
http://www.tvfool.com/?option=com_wr...dfafe2b1a0cef3

and even better at 75 feet, which you would probably need to get above the trees. Note that WCSH is now just as strong as the other NBC WLBZ on real channel 2 (would need a BIG antenna), which didn't get stronger:
http://www.tvfool.com/?option=com_wr...dfafe98602d14d



The terrain profile shows interference to the WCSH signal just before your location:

Attached Images
File Type: jpg frg34TVFmap3b.jpg (57.9 KB, 653 views)
File Type: jpg frg34TVFelevWCSH.JPG (107.2 KB, 621 views)
File Type: jpg frg34TVFp2WCSH.JPG (112.1 KB, 630 views)
__________________
If you can not measure it, you can not improve it.
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http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 31-Oct-2016 at 12:47 AM.
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Old 30-Oct-2016, 11:09 PM   #3
rabbit73
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Join Date: Aug 2012
Location: S.E. VA
Posts: 2,518
Here is a coverage map for WCSH. The NM changes for different heights, the green lines change for different heights, but the colors do not change for different heights. You are on the extreme fringe.

Signals weaker than NM -15 dB are impossible to receive because they are below the Thermal Noise Floor at -15 dB NM. If you are able to receive signals listed as weaker than NM -15 dB, either the tvfool report is wrong or the signal is stronger from tropospheric propagation (Tropo).

Note that only 685 kW ERP out of 1000 kW ERP are sent in your direction because of the directional transmitting antenna.



here is a closeup:

Attached Images
File Type: jpg frg34TVFcovWCSH.JPG (103.1 KB, 619 views)
File Type: jpg frg34TVFcovWCSHcu.JPG (113.9 KB, 616 views)
__________________
If you can not measure it, you can not improve it.
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Last edited by rabbit73; 30-Oct-2016 at 11:14 PM.
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Old 31-Oct-2016, 12:32 AM   #4
rabbit73
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Location: S.E. VA
Posts: 2,518
There are several possible antenna systems for your location.

System 1. A Winegard HD7698P aimed at 263 deg true and a Channel Master 7777 preamp. If you don't get Fox at 301 deg true, you will need to add a rotator. The Channel Master 9521A is popular, but it doesn't have long term reliability. You would need to upgrade to a ham (radio amateur) rotator like the Yaesu G-450 or Hy-Gain AR-40.
http://www.eham.net/reviews/products/24

If you must have WLBZ on VHF-Low real channel 2, you will need a BIG antenna like the Winegard HD8200U or Solid Signal HD8200XL.

System 2. An Antennas Direct 91XG or Solid Signal HDB91X aimed at 263 deg true for WCSH NBC and WGME CBS. A second antenna an MCM 30-2476 aimed at 262 deg true for WMTW ABC. Combine the two antennas with a UVSJ UHF/VHF combiner and connect to a CM7777. The two antennas should have their front end tilted up using the tilt feature to catch the signals coming down from the hill peak.

A third antenna a Solid Signal HDB91X aimed at 301 deg true and a second CM7777 preamp for WPFO Fox.

Bring down two coax lines, one from each preamp. Connect the outputs of the power inserters to an A/B switch to select which antenna system you want.

An alternate plan is to connect the antennas for NBC, CBS, and ABC to the antenna input of the TV and connect the Fox antenna to a separate tuner with its output connected to the aux input of the TV.

The advantage of the 3 antenna system is that a rotator is not needed, and the antennas are optimized for each channel. You wouldn't need to wait for the rotator to swing around, you wouldn't need to repair it in the middle of January, and you wouldn't need to rescan after changing directions if your TV isn't able to add a channel after scan.

If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge which will tend to discourage a strike, but the system will not survive a direct strike.

You will need a dual grounding block for two downleads.

__________________
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http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 31-Oct-2016 at 1:02 PM.
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Old 6-Nov-2016, 1:43 AM   #5
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,518
Quote:
Originally Posted by frg34
Thanks for posting for me and the detailed response: I appreciate it. Yeah, not sure getting much above 35 ft is realistic for me and the short trees around are 60+ feet.
You are welcome; I thought it was an interesting and challenging problem.

It is my hope that you will at least try to make a test. Sometimes the tvfool report is off, because it is only a computer simulation.
__________________
If you can not measure it, you can not improve it.
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http://www.megalithia.com/elect/aeri...ttpoorman.html
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