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AhmedGalal
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Limitations of Terrestrial UHF

09/18/2015 3:52 PM

Firstly I'm sorry if my question is Dumb I'm not a Communication Engineer , I'm production Engineer
What are the geographical limitations of tv reception system of terrestrial UHF ?
What if I used antenna array to increase gain ? Is that can help me receive far stations ,
Is Analog transmission has more coverage than Digital transmission
Thanks in advance
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Original_Macgyver
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#1

Re: Limitations of terrestrial UHF

09/18/2015 4:01 PM

First thing is to get an antenna that is the correct design to receive your specific frequency.

Now, get that antenna as high up as possible.

If there are stations that are received from a different direction then maybe a directional antenna or an array would work. However, you cannot just hook all the antenna together into one device, you'll be picking up interference from stray signals

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SolarEagle
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#2

Re: Limitations of terrestrial UHF

09/18/2015 4:14 PM

There is a ton of info online....

http://www.w6pql.com/antennas.htm

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lyn
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#3

Re: Limitations of terrestrial UHF

09/18/2015 6:16 PM

It sounds like you are new to rf communications.

You have a lot of reading to do:

Ultra high frequency - Wikipedia, the free encyclopedia

A Guide to UHF Television Reception | WTIU

How Far Can Two-Way Radios Communicate?

How the Radio Spectrum Works - HowStuffWorks

UHF Repeaters - How do they work?
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Anonymous Hero
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#4

Re: Limitations of terrestrial UHF

09/18/2015 6:20 PM

UHF is pretty much line of sight.

The higher the frequency the more direction the signal becomes. Microwave signals are even more directional.

As McGiver said, altitude helps because the coveter of the earth, hills, trees, and other obstructions disrupt the signal, much like a laser beam, but UHF does have some penetration power through buildings.

The further you are from the source the more gain your antenna needs to pull out a reliable signal. A general rule of thumb for the limit is about 70 miles, but that depends on what other objects are in the way, which can reduce the range and don't forget the transmitter power. If they don't produce a a powerful signal, the range goes down.

Digital isn't necessarily better for range. Digital is an all or nothing signal. Either you get a very good video and audio or it goes blank. Analog degrades with more and more noise in the signal, but can be useable at distances where digital has too many dropouts.

Your best bet is a hi gain antenna properly oriented and high in the air, with a high quality antenna feed line.

They make amplifiers to boost the signal, but they are not a magic wand. Not only do they amplify the signal, but they will amplify the noise. How far you come ahead depends on how good the amplifier is and just how weak the signal is.
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AhmedGalal
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#5
In reply to #4

Re: Limitations of terrestrial UHF

09/18/2015 7:49 PM

Thank you so much , your answer is pretty clear and helped me , terrestrial tv is not important to me , but some sports events like World Cup is free on it .
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lyn
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#6
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Re: Limitations of terrestrial UHF

09/18/2015 7:55 PM

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Anonymous Hero
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#7
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Re: Limitations of terrestrial UHF

09/18/2015 7:57 PM

If you want to get crazy you can stack or co-phase antennas to increase gain.

Two co-phased antennas will double the again (+3dB). Four will double the gain again for a total of +6dB.

However, you need to be careful about matching impedances on the feed lines.
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Tom_Consulting
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#8
In reply to #4

Re: Limitations of terrestrial UHF

09/18/2015 10:37 PM

GA - and consider adding a rotator to the antenna mount...that way you can point it towards different stations.

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Original_Macgyver
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#16
In reply to #4

Re: Limitations of terrestrial UHF

09/22/2015 10:33 AM

AH,

Good explanation. Your description is spot on!

GA from me too!

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HiTekRedNek
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#9

Re: Limitations of terrestrial UHF

09/19/2015 9:09 AM

If you live in the USA,use this map to determine the signal strength and direction to transmitters in range of your location.

http://transition.fcc.gov/mb/engineering/dtvmaps/

You can also try the internet for overseas broadcasts.It may be $$ per view.

Some things just are not free.

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HiTekRedNek
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#10

Re: Limitations of terrestrial UHF

09/19/2015 9:18 AM

A fairly recent development is Fractal antennae,which give lots of gain for their size,and there are plenty of web sites that give instructions on how to make your own.

Results vary,but if you have more time than money,it might be worth your efforts..and learn a little fractal geometry as a bonus..

Here is a link to get you started:

http://www.instructables.com/id/Indoors-Fractal-HDTV-Antenna/

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Anonymous Hero
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#11
In reply to #10

Re: Limitations of terrestrial UHF

09/19/2015 2:08 PM

I can't find anything that describes the theoretical gain (let alone the actual gain) for this antenna.

I have seen antenna theoretical plots for the $60 Winegard PR-8800 outdoor bow-tie HDTV antenna producing > 15 dBi of gain.

I suspect that the indoor fractal antenna will be closer to 3 to 6 dBi, but I would love to see some quantitative data.
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HiTekRedNek
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#12
In reply to #11

Re: Limitations of terrestrial UHF

09/19/2015 2:55 PM

The main advantage is in size.

A very small physical size can give a disproportionately long wavelength path.

They are used in cell phones for this reason.

Here is a link to get you started:

http://ictactjournals.in/paper/IJCT_March%282013%29_Paper_2_669_674.pdf

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#13
In reply to #12

Re: Limitations of terrestrial UHF

09/19/2015 3:56 PM

Thanks. very good article.

Seems you are still much better off with a good external antenna if you can do it.
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Legolaz
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#14

Re: Limitations of Terrestrial UHF

09/20/2015 9:01 AM

It did not come to mind that there was also likewise an Extraterrestrial UHF.

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#15
In reply to #14

Re: Limitations of Terrestrial UHF

09/20/2015 9:27 AM

Oh, if only we could find it!
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Users who posted comments:

AhmedGalal (1); Anonymous Hero (5); HiTekRedNek (3); Legolaz (1); lyn (2); Original_Macgyver (2); SolarEagle (1); Tom_Consulting (1)

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