Which ATSC OTA Frequency has the best coverage (LOS) generally speaking - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 29 (permalink) Old 2017-03-06, 12:54 AM Thread Starter
Rookie
 
Join Date: Jun 2016
Posts: 12
Which ATSC OTA Frequency has the best coverage (LOS) generally speaking

Which ATSC OTA (north america) Frequency has the most line of sight (generally speaking)

Example. in a perfect world in the ATSC UHF range, which frequency/channel would provide best coverage.


In real world, i do know 800mhz area is haywire due to LTE and cellular.

Channel 2/4 54mhz VHF ota, how does it compare to higher channel of 68 of mhz 797?

Thanks ( im not talking about a specific region,or station, but general technical info)
jewish_dave is offline  
Sponsored Links
Advertisement
 
post #2 of 29 (permalink) Old 2017-03-06, 02:57 AM
Veteran
 
Join Date: Dec 2006
Location: Calgary AB
Posts: 4,013
Lower frequencies generally can travel further and overcome obstacles better.


Sent from my iPad using Tapatalk
BGY11 is online now  
post #3 of 29 (permalink) Old 2017-03-06, 02:59 AM Thread Starter
Rookie
 
Join Date: Jun 2016
Posts: 12
Hi Bgy, that i understand but at what cost? lower bandwidth?
jewish_dave is offline  
 
post #4 of 29 (permalink) Old 2017-03-06, 09:18 AM
 
Join Date: Dec 2008
Location: Mississauga
Posts: 774
The 6 MHZ bandwidth stays the same.

FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR[SIZE="1"
Jorgek is offline  
post #5 of 29 (permalink) Old 2017-03-06, 10:16 AM
 
Join Date: Nov 2009
Posts: 509
Generally speaking, the higher the frequency of the RF signal, the more line-of-sight is its propagation. The lower the frequency of the RF signal, the more readily the signals will "bend" over terrain, the curvature of the earth, and the like.

It's all in the math. If you want to study further and understand the math, suggest you research "RF Fresnel zones" and "RF path loss calculations". The math does get complicated very quickly.

Good luck.
ProjectSHO89 is online now  
post #6 of 29 (permalink) Old 2017-03-06, 10:42 AM
Veteran
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 5,787
Which ATSC OTA Frequency has the best coverage (LOS) generally speaking

There is no general answer. It depends on a number of variables. Under perfect LOS conditions lower frequencies have an advantage due to larger antenna size and lower attenuation from atmospheric conditions. Without LOS and minor obstacles lower frequencies definitely have an advantage. That is countered by increased interference from RF noise and more distant stations. It's even more difficult to make a general statement due the fact that changing atmospheric conditions result in different results due to seasonal and other factors that can vary on an hourly basis. What can be shown in a lab or with mathematics does not always reflect what happens with OTA due to an almost infinite number of variables in real world situations.
ExDilbert is offline  
post #7 of 29 (permalink) Old 2017-03-06, 03:01 PM Thread Starter
Rookie
 
Join Date: Jun 2016
Posts: 12
so lower frequencies require a large antenna ?
jewish_dave is offline  
post #8 of 29 (permalink) Old 2017-03-06, 03:58 PM
DHC Supporter
 
Join Date: May 2010
Location: S.E. VA
Posts: 687
Yes, the lower the frequency, the longer the elements. Just like organ pipes; the low notes use longer pipes. It is called the resonant frequency.

The UHF elements are the shortest. VHF-High elements (real channels 7-13) are about 3 times as long as UHF elements.

VHF-Low elements (real channels 2-6) are about 3 times as long as VHF-High elements.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
rabbit73 is offline  
post #9 of 29 (permalink) Old 2017-03-06, 04:05 PM
 
Join Date: Nov 2009
Posts: 509
Quote:
What can be shown in a lab or with mathematics does not always reflect what happens with OTA due to an almost infinite number of variables in real world situations.
Absolutely, but the math is essential to understanding how it's supposed to work. Once one understands the underlying concepts, it's a lot easier to understand and explain the seemingly infinite permutations that occur in the "real world".

Quote:
so lower frequencies require a large antenna ?
Generally, yes, if you're to compare antennas of comparable performance. It has to do with wavelength and the speed of light (radio waves). More math again.
ProjectSHO89 is online now  
post #10 of 29 (permalink) Old 2017-03-06, 09:02 PM
Veteran
 
Join Date: Apr 2004
Location: derry + winston Mississauga
Posts: 1,509
With digital transmission most broadcasters have desired to be on UHF band.IF you have LOS than higher the frequency the better.The theatrical range is further on lowest frequency.If best means most reliable LOS reception then highest frequency.

Attic CM 4248 at Buffalo,M4 at Buffalo.VHF yagis at Toronto .
rob50312 is offline  
post #11 of 29 (permalink) Old 2017-03-06, 10:56 PM
Veteran
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 5,787
The only reason UHF is favored now is because effective radiated power (ERP) was set too low for VHF ATSC stations. It's an example of where the people doing the math were wrong when it came to calculating real world TV coverage.
ExDilbert is offline  
post #12 of 29 (permalink) Old 2017-03-07, 07:06 AM
Veteran
 
Join Date: May 2009
Location: Mississauga
Posts: 7,341
Quote:
so lower frequencies require a large antenna ?
All else being equal, a lower frequency requires a larger antenna. Antenna element size depends on wavelength, which is inversely proportional to frequency. The relationship is wavelength in metres = 300 / frequency in megahertz. Or frequency (MHz) x wavelength (M) = 300.

I haven't lost my mind. It's around here...somewhere...
JamesK is online now  
post #13 of 29 (permalink) Old 2017-03-07, 09:59 AM
Veteran
 
Join Date: Jul 2005
Location: Craig Henry (Greenbank/Hunt Club), Nepean, ON
Posts: 3,158
The other issue is that all frequency planning is based on the mythical outdoor antenna mounted at 10m above ground.
While VHF propagates better outdoors, the longer wavelength has more trouble entering building -- look up aperture for a discussion of the differences between indoor VHF and UHF reception.

In addition to underestimating the noise environment at VHF outdoors, they drastically underestimated the higher VHF noise environment indoors.
tvlurker is offline  
post #14 of 29 (permalink) Old 2017-03-07, 10:39 AM
Veteran
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 5,787
Lower frequencies (VHF) penetrate buildings better than higher frequencies (UHF.) UHF frequencies penetrate buildings adequately but VHF are better at penetrating or circumventing almost any man made or natural obstacle. Unfortunately, noise levels in modern urban environments, which are stronger at lower frequencies, negate that advantage and create havoc with ATSC, more so due to the low ERP used for TV stations.
ExDilbert is offline  
post #15 of 29 (permalink) Old 2017-03-07, 11:57 AM
Veteran
 
Join Date: Apr 2004
Location: derry + winston Mississauga
Posts: 1,509
Low frequencies do not penetrate buildings better.Drive your car underground parking and see how your AM reception is compared to FM.

Attic CM 4248 at Buffalo,M4 at Buffalo.VHF yagis at Toronto .
rob50312 is offline  
Reply

Tags
atsc , ota

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