OTA Mounts, Towers, Rigging Hardware - Page 3 - Canadian TV, Computing and Home Theatre Forums

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post #31 of 2047 (permalink) Old 2005-10-04, 02:26 PM
 
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Cool Calculating bearing and distance to TV broadcast antennas

I've just gone through the exercise of determining the proper bearing given my specific location and though I'd share with everyone else how to do this -- and in the progress figured out that I'm a good 20 degrees off of where I should be pointing!

(An excel spreadsheet helps for this)

1) Go to google earth, and download the free explorer. Find your home on the map, and take down you exact latitude and longitude coordinates.

2) Go to http://www.fcc.gov/mb/video/tvq.html and search for the city you'd like to aim for. In Ontario that city is typically the CN tower, buffalo and/or rochester. Take down the bearings of a few of the stations' antennas you are shooting for.

3) Use the tool at http://www.movable-type.co.uk/scripts/LatLong.html to find out the exact bearing you should be aiming for. This bearing produced for people in Ontario (and BC as well) should be EAST of North.

(Almost there!)

4) Use the Natural Resources Canada declination calculator to find the difference between magnetic north and true north in your area: http://gsc.nrcan.gc.ca/geomag/field/mdcalc_e.php
In Toronto it is 10.4 degrees west of north. Meaning the needle will point 10.4 degrees west of north when you are facing true north. In Toronto this means you will ADD the 10.4 degrees declination to any bearing you get from step 3.

5) Grab/borrow a (decent) compass. Align your antenna to compromise between all the stations you are looking to receive from. Be sure to factor in declination (difference between magnetic and true north).
If you do not have any serious geographical or man-made obstacles you should be in business! Enjoy!

Gordon
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post #32 of 2047 (permalink) Old 2005-10-04, 02:49 PM Thread Starter
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Calculating proper compass bearings to TV broadcast antennas

Quote:
Originally Posted by gordee78
I've just gone through the exercise of determining the proper bearing given my specific location and though I'd share with everyone else how to do this -- and in the progress figured out that I'm a good 20 degrees off of where I should be pointing!
That's great info, and locations of all Canadian TV transmission antennas can be found at:

http://www.user.dccnet.com/jonleblan...a_TV_Stations/

while U.S. ones can be found at:

http://www.fcc.gov/fcc-bin/audio/tvq.html



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post #33 of 2047 (permalink) Old 2005-10-04, 02:55 PM Thread Starter
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Just one thing though to rain a bit on the parade: don't forget to consider the terrain between your receiving antenna and the broadcast antennas. Numbers are terrific to have, but bear in mind the difficulties posed by elevation changes and/or obstructions, such as between Vancouver and Seattle, or below the Niagara Escarpment from Buffalo.



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post #34 of 2047 (permalink) Old 2005-10-05, 10:39 AM
 
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Location: Markham -- Bayview & Steeles
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One thing to remeber, the inclination/declination really doesn't have much affect if the stations are in a N.W - S.E. direction, and at most the effect is only 1 or 2 degrees -- not really enough to affect the signal.

Also, if you know your lat/long, a good site to give you all the stations in your area and the distance/direction is:

http://www.2150.com/broadcast/default.asp
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post #35 of 2047 (permalink) Old 2005-10-05, 11:03 AM
 
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Quote:
Originally Posted by intrac
One thing to remeber, the inclination/declination really doesn't have much affect if the stations are in a N.W - S.E. direction, and at most the effect is only 1 or 2 degrees -- not really enough to affect the signal.
Just want to clarify here: What's declination got to do with affect on the signal? If someone has a compass and does not take into account the effects of declination then they would be off more than 10 degrees in Toronto! Wherever the compass holder is (regardless of where the stations are) they should take into account that their needle will be pointing at magnetic north ... and all the topographic maps and lat/long coordinates and bearings will be based on TRUE north measurements.
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post #36 of 2047 (permalink) Old 2005-10-05, 11:17 AM
 
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Quote:
Originally Posted by gordee78
Just want to clarify here: What's declination got to do with affect on the signal? If someone has a compass and does not take into account the effects of declination then they would be off more than 10 degrees in Toronto! Wherever the compass holder is (regardless of where the stations are) they should take into account that their needle will be pointing at magnetic north ... and all the topographic maps and lat/long coordinates and bearings will be based on TRUE north measurements.
The effect of declination is the same at both ends of the measurment, so the net effect is that your direction is essentially unchanged. Also, with an antenna distance measurement, you are only looking at between 50 and 100 miles.

There could be an affect on signal, because your aim will be off - it depends on the antenna beamwidth.
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post #37 of 2047 (permalink) Old 2005-10-05, 02:11 PM Thread Starter
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I agree with both of you. I live next to a street that runs north-south and was originally chained (surveyed) using the nearest meridian and not compasses. Since my own antenna and the broadcast transmission antennas are at fixed geographic coordinates, I can determine the difference in position (in degrees) using arithmetic to arrive at the correct angle. Then its possible to line up my antenna north-south with that street and turn it the appropriate amount of degrees. Without such a reference it would be necessary to do it by compass, at which point the factoring of declination will be necessary.



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post #38 of 2047 (permalink) Old 2005-10-05, 03:19 PM
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Here is another inverse tool from NRCan.

The tool is for accurate azimuth determination. The ellipsoid to use is GRS80 but really any will do with the accuracy we are talking about here.
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post #39 of 2047 (permalink) Old 2005-10-20, 07:04 PM
 
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Securing 10' Mast

Anyone have pics or suggestions on how to secure the mast holding a cm4228 and a rotator? Over the past 2 weeks (2 days in particular with high winds) I have noticed that my 10' mast has bent to the right. Unfortunately this has become a problem as while I am still able to pull in CTV/CITY with the rotator - I have lost significant signal strength on the US feeds (averaging 60-70%). I've noticed that due to the bend the antenna is now tilted downwards a tad... Its currently mounted to the chimney but I'm thinking either the pole needs replacing or I need to reconsider the mount altogether. I don't have a current pic of the problem but I do have the original setup (a few months back) when it was really working out.. Now I'm not so sure anymore... any suggestions?

old pics
http://photobucket.com/albums/b233/open6l/
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post #40 of 2047 (permalink) Old 2005-10-20, 07:08 PM
 
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Actually my mistake - I do have a few shots in there.. the bend is actually a bit worse now and that white discoloration is some old duct tape that was on the pole - its not due to the bend...
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post #41 of 2047 (permalink) Old 2005-10-20, 09:07 PM
 
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Location: Waterford, Ont
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Quote:
Originally Posted by open6l
actually my mistake - I do have a few shots in there.. the bend is actually a bit worse now and that white discoloration is some old duct tape that was on the pole - its not due to the bend...
A taller tower and a shorter pole.

Panasonic PT47WX53, Humax HFA100, Denon AVR 1610 surround, CM4228 Antenna, WD TVlive
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post #42 of 2047 (permalink) Old 2005-10-20, 09:29 PM
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Location: 300 Steelcase Road W, #20 Markham,905470 9604 ext 230
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open6l I know what your problem is.

The size of your 10' pole is too thin for what you are doing.

From your pictures your pole looks too thin, what size are you using 1 1/4" ID?

You need atleast a 1 1/2" ID to 1 3/4" ID for the free standing 10' pole with a rotor with a antenna like a 4228 on top. The rotor can mount take to a 2.0" diamater pole.

My suggestion is that it looks like you already have a clear view for the ota signals, from your roof there is no reason to go that high.

I would recommend you use a 5 to 6' pole against the chimmney at least 1 1/4" to 1 1/2" ID pole that it clears the chimmey by a 1 or 2' the most.

From there use the balance of the pole enough to mount your rotor and 4228 on top.

With the second pole on the rotor make sure the length is just enough to mount the antenna, you should not use no more than 40".

The loading(the weight of the rotor and antenna) that you have with your current setup is too much to support a free standing 10' with the rotor.

As long as your antenna has a clear view then that is as tall as you need to go. If you really want to go tall then I would suggest a tower.

CM4228/9521/7775;F.RmJvc70FH96/8300HDPvr/Dish 612;B.Rm LC52LE810UN/8642HD;Study LG50PK550/Xbox360;

Last edited by Yaamon; 2005-10-20 at 09:48 PM.
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post #43 of 2047 (permalink) Old 2005-10-20, 09:56 PM
 
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The pole is 1-1/4 and the 2nd pole is 36"... Before the rotor it was quite secure but i noticed after the rotor that it wasn't as good... thought about what you said - maybe i'll cut it down to 5' instead - would you also recommend 1-1/2" or is the 1-1/4" fine for 5' ?
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post #44 of 2047 (permalink) Old 2005-10-20, 10:04 PM
 
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btw - how far does clear view need to be? I mean I have the tallest roof of the neighborhood with no immediate trees blocking (other than the mini forrest off in the distance).. is that ok in terms of clearance?
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post #45 of 2047 (permalink) Old 2005-10-20, 10:15 PM
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Location: 300 Steelcase Road W, #20 Markham,905470 9604 ext 230
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open6l from your pictures your view is clear that is why you dont need to go as high.

Yes you can use back your pole, just cut it down make it long enough that it clear the chimmney by 1 to 1.5'

Then from there use the piece of 36" pole as you have it with your rotor.

By doing that the pole will be very sturdy like being only 2' out as the lower parts are braced against your chimmney.

Yes the install before the rotor was perfect. Nice job, I would have reduced that length of pole as your view seems clear. 7' free standing with a 4228 is on the edge for the weight of a 4228.

CM4228/9521/7775;F.RmJvc70FH96/8300HDPvr/Dish 612;B.Rm LC52LE810UN/8642HD;Study LG50PK550/Xbox360;
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