Antenna Height - why it is important, what are the benefits
Ғылым және технология
The height of a radio antenna or radio aerial can have a significant impact on its performance, especially at VHF and UHF. We often see many forms of radio antenna mounted on tall masts or towers or they may be mounted on the tops of buildings, fixed to chimneys fixed to the sides of the buildings and the like.
We see many VHF and UHF television antennas mounted on the tops of houses, and mobile phone and other telecommunications antennas are often mounted on towers. The antenna height is obviously very important.
There are several reasons for this:
It can be imagined that a clutter free signal path will enable a better signal to be received and this is true. An antenna mounted high up is more likely to be able to achieve this.
Like there is a visible horizon, the same is true for radio signals. Mounting the antenna high up extends the radio horizon and hence the coverage. It is possible to calculate the distance to the radio horizon very easily.
A high antenna also helps when there are hills or even just undulations in the surface of the Earth.
Additional benefits are gain from antenna height. It stands to reason that a high antenna will be further away from sources of interference.
Similarly for a transmitting situation, if the radio antenna is mounted high up, the radiation levels will be reduced in any buildings.
However it is necessary to remember there will be other considerations when antennas are mounted high up. High antennas may be more difficult to maintain as they will be more difficult to access. They may also be more exposed to t e weather and storms, so a well installed antenna is essential. Also high antennas will need a longer feeder or coaxial cable. It is essential to use low loss coax - use the lowest loss that is reasonable. This is particularly important for VHF and UHF antennas that are high up because feeder loss is higher at these frequencies than at lower frequencies.
For more information about antenna height and why it is important check out our web page: www.electronics-notes.com/art...
Check out the Electronics Notes website: www.electronics-notes.com
Please don't forget to subscribe to our KZread channel: kzread.info?...
And please don't forget to "like" the video
Пікірлер: 25
I love dipping into your notes and this one is no exception. For me, it is sometimes revision and sometimes new learning. When watching for revision, I usually learn some new things too. Thank you.
@ElectronicsNotes
Жыл бұрын
Thanks for sharing this. I am really delighted you find the videos and website useful.
Great explanation
@ElectronicsNotes
4 ай бұрын
Thank you. I’m really glad you found the video useful.
a older guy told me years ago about antennas he said the truth about antennas was ALWAYS ALWAYS Height = Might No mater What and some 35-40 years later I Know This To Be True ..lol. I have experienced it time & time again over the years as has every one else who has ben around antennas very long !
@ElectronicsNotes
Жыл бұрын
Yes, height is might for antennas is a great way to sum everything up about antenna height. I suppose you have summarised in three words what I explained in the video. Thanks.
Thanks for your efforts
@ElectronicsNotes
2 жыл бұрын
Glad to help.
Another factor in VHF/UHF range is the attenuation of foliage at higher frequencies, this is most noticeable when operating direct mobile to mobile. On 2 meter ham radio I've gotten the best performance for the cost of height by placing my base antenna sticking out of the top of a tall tree next to my home to get it above the average tree top level. I could use repeaters up to 100 miles away with this. Of course the higher you go, the longer your coax cable run, the more loss between the radio/TV and the antenna, so you'll need to get better coax cable to reduce signal loss. For TV a good mast mounted preamplifier makes a lot of improvement in your received signals even with cheaper coax cable. In the States I've had excellent results using the Channel Master 2222 TV preamp. 73 mike
@ElectronicsNotes
5 ай бұрын
That’s really interesting - thank you. Certainly foliage does make a difference and your innovative way of overcoming it is very good! Thanks again for your comment.
Very helpful thank you
@ElectronicsNotes
Жыл бұрын
Glad the video was helpful. Thanks for the comment.
Another tip is, watch your antenna gain when going up high. a higher gain antenna has a flatter signal path, you be right underneath it, and have a much weaker signal than someone 20 km's away - but this works also both ways, the TX antenna gain and the receivers antenna gain, if they are both, say 12db, you might not even crack open a repeaters squelch. It's why antennas on appartments are 6-12db, on top of high hills 3-6db , this takes into account 90% of hand helds atre 0-3db, and cars are 4.5-6db.
@ElectronicsNotes
2 жыл бұрын
This is a good point. Often broadcast antennas have some separate antennas beamed downwards to give local coverage.
CAN ANTENNA GIVE OFF LETHAL RADIATION SIGNALS HARMFUL TO PEOPLE IF ITS INSTALLED INSIDE A HOUSE?🤔
@soha150
2 жыл бұрын
It depends on the amount of power radiated through these Antennas If you radiate over 360 watt of power -based on FCC regulations- then you are in the danger zone of getting harmed by the radiation Another factor is the frequency of the radiated electromagnetic wave the more frequency the less the wave propagate -in general matter- and less harm to humans, until you reach X-rays frequency then the harm-ness is way bigger. I hope I answer your Q
@microminiskirt
2 жыл бұрын
@@soha150 THIS WOULD BE ON 2 METER BAND NO MORE THAN 80 WATTS.
@soha150
2 жыл бұрын
@@microminiskirt 2-meter band is 144 Mhz to 148 Mhz and this frequency can penetrate wall and human body, 80 watt for long time is diffidently harmful if you are about 10 meters away from it or less. What kind of antenna is used?
@microminiskirt
2 жыл бұрын
@@soha150 A GP2 COMET PROPOSED BUT DID NOT GET IT. IN BUILDING STAGE DUE TO LIVING SITUATION.
@ElectronicsNotes
2 жыл бұрын
If a radio antenna is used for reception there is no danger. If it is used for transmitting, then there can be issues with electromagnetic radiation intensity. With low power transmissions there is normally no need to worry at all. If the transmitter power is higher, then there could be a concern. It is always best to have transmitting antennas outside and away from people.
The most important factor in your subject is Fresnel Zone Yet you never mentioned it
@ElectronicsNotes
2 жыл бұрын
May be another video topic.
𝔭𝔯𝔬𝔪𝔬𝔰𝔪