Tilting Antenna for Better Reception - Page 3 - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #31 of 64 (permalink) Old 2009-06-28, 09:52 PM
 
Join Date: Apr 2009
Location: Ottawa
Posts: 502
Question Optimal Antenna Elevation angle

What is the best elevation angle to set an antenna at for LOS receiption? I am pretty much in the highest spot in the immediate relatively flat neigbourhood and I have currently set my antenna to point pretty much horizontal. I know that if there is some obstruction nearby then one should aim for the top of this obstruction as the adjusted horison. However, as in my case, would there be a significant amount of receiption coming in at above zero elevation angles due to atmosperic "bending" of the electro magnetic propagation? I can imagine that for long distances this may be more important but what about the LOS case where the transmitting tower is about 20miles away?
RamKat is offline  
Sponsored Links
Advertisement
 
post #32 of 64 (permalink) Old 2009-06-28, 11:19 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
The only thing you can do is experiment, it varies at each location and can vary over the course of a day.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #33 of 64 (permalink) Old 2009-06-29, 06:23 AM
 
Join Date: Apr 2009
Location: Ottawa
Posts: 502
Quote:
The only thing you can do is experiment, it varies at each location and can vary over the course of a day.
I wonder about the SW model that the folks at TVfool uses. When I worked in the Infra red field a couple of decades ago we had an atmospheric model, called LOWTRAN, to predict the transmission of infra red through the atmosphere. This model took into account changes in atmospheric conditions and broke the atmosphere up into layers with characteristics of every layer defined. Standard libraries existed for say tropical, sub tropical etc conditions and the seasons of each of these areas which one could use and modify for the local condition of interest including atmospheric pressure, temperature, humidity, visibility etc. I am sure that something similar should exist for the UHF band. The optimal angle would probably also change for each frequency so it may not be a set angle and as you say it may change throughout the day and seasons.
RamKat is offline  
 
post #34 of 64 (permalink) Old 2009-06-29, 09:57 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
I am sure that something similar should exist for the UHF band.
I think the guy who does the tropo ducting forecast would have that info. Try following back thru the site. http://www.dxinfocentre.com/tropo.html

Also, LOS infra red light wouldnt be affected like uhf is by ground conditions. So, not only do you have to look for the signal coming in at say plus 20 degrees, it could also be coming in at a minus 20 degrees angle. Its always a compromise and an experiment, heh.

Quote:
I can imagine that for long distances this may be more important but what about the LOS case where the transmitting tower is about 20miles away?
I think youre right about that. At 20 miles, the bounce angle from the atmosphere would have to be extremely sharp.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #35 of 64 (permalink) Old 2009-06-29, 12:10 PM
OTA Forum Moderator
 
Join Date: Jan 2005
Posts: 24,879
RamKat I think you missed the original thread so I've merged yours into it - see the previous posts for more advice on tilt.
stampeder is offline  
post #36 of 64 (permalink) Old 2009-06-29, 12:14 PM
OTA Forum Moderator
 
Join Date: Jan 2005
Posts: 24,879
Large bodies of water between TV antennas and stations can also require tilting to try to get over the "Lake Effect" or as we now call it on Canada's west coast, the "Straight Effect".
stampeder is offline  
post #37 of 64 (permalink) Old 2009-06-29, 01:08 PM
 
Join Date: Apr 2009
Location: Ajax, Ontario
Posts: 285
I heard Lacrosse is basically a 'DB2' in disguise. So I can do the same for my CM4221HD bowtie given that I have to aim across the lake to Grand Island.

I have a satellite J pipe with tilt feature. Hmmm...I have to do some thinking how to retrofit it to my stacking bowties.
kooguy is offline  
post #38 of 64 (permalink) Old 2009-06-29, 07:35 PM
 
Join Date: Apr 2009
Location: Ottawa
Posts: 502
Quote:
Large bodies of water between TV antennas and stations can also require tilting to try to get over the "Lake Effect" or as we now call it on Canada's west coast, the "Straight Effect".
Would this be to get a multipath out of the sensitive part of the vertical gain in order to improve the LOS to reflected signal strength ratio?

I had similar issues with infra red transmission over a body of water - had to add a special blanking algorithm to get rid of that.
RamKat is offline  
post #39 of 64 (permalink) Old 2009-06-29, 08:34 PM
Veteran
 
Join Date: Jan 2009
Location: Montreal
Posts: 2,421
as a practical matter, I wonder how many people actually tilt, I imagine its more fringe areas, also doesnt that become a strain if a rotator is involved...
balm is offline  
post #40 of 64 (permalink) Old 2009-06-30, 12:06 AM
Veteran
 
Join Date: Nov 2006
Posts: 1,543
Quote:
Originally Posted by balm View Post
as a practical matter, I wonder how many people actually tilt, I imagine its more fringe areas, also doesnt that become a strain if a rotator is involved...
Tilting about the centre of gravity shouldn't affect the rotor at all.
That's how the (home built) manual tilt on our big array here does it.
mlord is offline  
post #41 of 64 (permalink) Old 2009-06-30, 12:11 AM
Veteran
 
Join Date: Jan 2009
Location: Montreal
Posts: 2,421
mlord,


did you post any pics of your home-built tilter, thanks
balm is offline  
post #42 of 64 (permalink) Old 2009-06-30, 12:28 AM
Veteran
 
Join Date: Nov 2006
Posts: 1,543
Quote:
Originally Posted by balm View Post
mlord, did you post any pics of your home-built tilter, thanks
Mmm.. I think the only possibly okay photo I have of it is this one:

[deleted -- better image below now]

The mast from the rotor extends straight up to the mid point of the antenna. The antenna is on a separate mast, hinged at the midpoint where it attaches to the mast from the rotor.

The tilt gets manually adjusted by removing a bolt from the bottom adjustment rail, repositioning it, and reinserting the bolt again.

I have parts and plans to motorize it, but that hasn't happened yet.

The blob behind the antenna is a scrap of eavestrough downspout, acting as a weatherproof housing for the preamp and 2:1 combiner.

Cheers
mlord is offline  
post #43 of 64 (permalink) Old 2009-06-30, 12:34 AM
Veteran
 
Join Date: Jan 2009
Location: Montreal
Posts: 2,421
thanks, thats sharp! so now I see the bottom adjustable brace is very supportive...

what can we use as a hinge, can a simple bolt system be used thru the two pipes, or is that an oversimplification!
balm is offline  
post #44 of 64 (permalink) Old 2009-06-30, 10:35 AM
Veteran
 
Join Date: Nov 2006
Posts: 1,543


The "hinge" is just a couple of T-brackets: bolted to the antenna mast (left), and attached to the tower/rotor mast (right) via a single bolt/nut, so it can pivot freely (yet securely).
mlord is offline  
post #45 of 64 (permalink) Old 2009-06-30, 11:04 AM
Veteran
 
Join Date: Nov 2006
Posts: 1,543
And to answer the obvious unasked question: Yes, it is absolutely rigid, with zero flex even when subjected to very high winds.

Cheers
mlord is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome