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Automated scanning yagi uda antenna for TV by using micro controller.

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deus

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sorry, i'm thinking to design a yagi uda antenna for TV that can automatic scan the directivity,gain,
beamwidth and major lobe for the the direction of strong signal of the transmitted EMW that can be received by TV.
I think to divide the sector of the beam width either 90/120, thus the yagi uda antenna can scan in one sector once the signal is not strong can shift to another sector until it find the strong signal and stops.
Actual my project will deal with measuring antenna parameters automatic by scanning into divided sectors by using microcontroller to determine the direction of the strong signal rather than using manual or rotating an antenna while looking to TV if showing clear display/pictures.
please, i'm requesting your help in what things to consider,which components can i include and if not worse even analysis for the advice.
thank you for consideration and i'll be glad for your coorperation
 

You should measure signal strength at the antenna input while observing multi-path fading.Because signals can arrive from multi points to the antenna ( reflections, diffractions) and the create fadings ( multiple images ) at the TV receiver.
If the signals are digital, it's much more easy to find the right direction by measuring BER at the TV receiver.Digital TV receivers have always a RSSI/BER outputs.
 

Are you asking for an automatic antenna positioner so you get best TV reception or a device to measure the performance of a TV antenna?

You mention directivity, gain, beamwidth and major lobe which can only be measured in controlled conditions but then mention 'clear display/pictures' so I'm not sure what you are trying to achieve.

Brian.
 
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    deus

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This strikes me as a 50% mechanical engineering problem. For measuring the performance of aerials using the local TV transmitters as your test source:- You need to rotate the aerial by at least 370 degrees so you can measure its back to front ratio. so you need limit stop microswitches, gearbox, motor, angle measuring kit. If you are hunting for the strongest TV signal, then you need the previous list but the angle measuring kit is not critical. But you will need to scan every TV channel quickly as the aerial rotates slowly, to find the channel with the highest field strength. If you are searching analogue TV , then looking at the sync pulses will tell you if you have bad echos.
Frank
 

exactly sir,my intention is to have an automatic antenna direction positioning to get the best Tv reception.The real objective of this project is to avoid the human intervention during the installation of TV antenna ,people try to guess the direction of the strong signal or best reception by rotating an antenna until he/she the reception is best
 

The cost of the aerial rotator and cabling would treble the cost of the aerial installation. If you intend to use this device to locate the best TV then orientate someone elses aerial to the same direction, it would be much easier to get the coverage maps for your local transmitters and a magnetic compass.
Frank
 

Yes Mr.Frank. you mean should I have the saver/database of the coverage information and direction of the transmitter so as to compare form the scanning receiving antenna? and how the magnetic compass can be used to detect the strong signal of EMW at receiving antenna?
 

Thank you Mr.Frank for your elaboration and helping comments. but sorry can you try to say something about the interfacing of a gearbox or its real functional part in this project
 

I had an antenna rotator sold by Radio Shack. Cost $70 circa 1990.

We were located 40 miles from the main group of transmitting towers. We wanted to watch tv stations which were located in various directions. Our roof aerial could bring in strong stations, but weak stations were snowy.

The rotator definitely improved our tv reception. Sometimes a few degrees made a big difference in quality.

A few times there was a double image. I guess that was multipath.

It came with a box which we placed near the tv. It had a rotating dial which was labelled with directions of the compass. We turned the dial in the direction we wanted the antenna to move. There were 4 wires going outside to the rotator, to power its motor.

I had to make sure the antenna was aligned in the direction that the dial indicated. I would turn the dial to point 'E'. Then I went outside to see if the antenna was pointed east. It was easy for them to get out of alignment.
 

As per Brads reply unless you have a worm and gear drive somewhere between the motor and the aerial, the action of the wind on the aerial will move it around. Also because of the amount of torque required to rotate an aerial a direct drive motor would have to be large and once the aerial is rotating would spin it too fast. A small motor with a big reduction gear box is the only sane way to go.
Frank
 

As per Brads reply unless you have a worm and gear drive somewhere between the motor and the aerial, the action of the wind on the aerial will move it around. Also because of the amount of torque required to rotate an aerial a direct drive motor would have to be large and once the aerial is rotating would spin it too fast. A small motor with a big reduction gear box is the only sane way to go.
Frank

Dear friends, please stop wasting your time on a nonsense!
When the TV was tansmitted as a VSB analog signal, the antenna pointing procedure was rather subjective, as not only the maximum signal amplitude was the goal, but also avoiding multipath "ghosts" were to be avoided.
With digital TV transmission, terrestrial propagation is gradually being phased out, and replaced by cable and satellite channels, without antenna problems. Digital TVs and set-top boxes do utilize certain algorithms to optimize the "picture", but the technical problem of signal error rate results only in stopping reception. No output is provided for an user to try antenna positioning and its possible effect on signal improvement.
Due to the above, please do not waste your time. Get a satellite or cable and live with many nice programs including multi-channel audio, without troubles with terrestrial propagation which will cease soon anyway.
 

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