mark Posted September 8, 2005 Report Share Posted September 8, 2005 hi What are the standards to be considered in the design of antenna for television... plsssssssssssss help me Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 8, 2005 Report Share Posted September 8, 2005 Hi Mark,Do people still use TV antennas where you are? In my city, nearly everyone has cable or satellite TV.They were 300 ohms for the 1st million years, but maybe you can buy them today at 75 ohms to match coax cable to the TV.Look on Google for my story about the TV antenna I had about 35 years ago that was on a rotor and was the biggest ever made.The antenna must be polarized correctly. Most TV transmitters today use horizontal polarization but England started broadcasting TV vertically (big mistake) because they didn't have any skyscrapers for it to bounce off, and were worried about ground reflections.Of course the dimensions of the antenna must match the frequency or band of frequencies required. About its only standard would be for it to be strong enough to hold enough pigeons. ;D Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted September 8, 2005 Report Share Posted September 8, 2005 It depends on where you live, here in the UK we use 50ohms. Quote Link to comment Share on other sites More sharing options...
Guest 1st Mil-Tech Posted September 13, 2005 Report Share Posted September 13, 2005 If you really want the the whole truth go here:http://www.kyes.com/antenna/antennadex.html Quote Link to comment Share on other sites More sharing options...
ECET0purdue Posted September 13, 2005 Report Share Posted September 13, 2005 audioguru......you got a pic of that pigeon holder ?Cheers Glen Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 13, 2005 Report Share Posted September 13, 2005 There is a local company making TV antennas for farmers and other people living away from the cable-TV in the city.It is a very expensive antenna made from the cardboard tube that carpet is shipped on, with a spiral of aluminum foil on its surface. It is sold and installed with a rotor and tests have shown that it works very poorly, but millions are sold. ;D ;D Quote Link to comment Share on other sites More sharing options...
John Biles Posted November 27, 2005 Report Share Posted November 27, 2005 Hello Mark,I live in Australia where a high percentage of people still have TV antennas and watch free to air TV.I have change over to Digital free to air in the last 2 months because I was told that if you have bad reception Digital would be the magic fix you need.I would like to say "What a Load of Crap!!" As Digital is just as hard to get as Analog, even harder at times.The reason I bring up this story is that I live 80-90 Kms away from the TV transmitters in a small town and have spent the last 2 months in the shed and on the roof of my house experimenting with Yagi Antenna designs and only finished the final design today. What I have learnt about antennas over the last 2 months is amazing. Compared to Audio electronics, RF electronics is a whole different world. To me it is amazing that a piece of tube cut to the right length and placed near a couple other tubes can generate and transfer enough energy to make the difference between having no Picture and perfect reception.To make an antenna is not that hard. What I would do is go buy a ready made antenna from you local hardware shop with a boom Length of no less than 2000mm pull it apart and with the link to a online Yagi program that lets you enter the frequency you want etc designs a antenna straight away. all you have to do is print out the design, transfer the details to to the boom, cut the elements to length and put it all back together and you now have an antenna that will give you a starting point to getting good reception.The link is www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf.html#Element_Dia Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 27, 2005 Report Share Posted November 27, 2005 Years ago I bought the biggest and best all-channels yagi TV+FM antenna that was made.With a rotor I got up to 3 distant cities' signals on the same channel, on a few channels.Its range was much farther than the TV guide in my newspaper.I could rotate it to pick a good reflection from a building to minimize ghosting from local stations.It was very difficult to install the huge heavy beast then reinstall it after a windstorm or dinosaur-bird toppled it. It still rotated and worked fine when it was hanging upside down, like in down-under.G'day, mate! ;D Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted December 1, 2005 Report Share Posted December 1, 2005 hi audioguru!do the video(AM) and audio signals(FM) in a TV come from the same antenna.i guess they differ in frequency by a large amount.how do they travel after antenna in same single wire? Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 1, 2005 Report Share Posted December 1, 2005 do the video(AM) and audio signals(FM) in a TV come from the same antenna?Of course they do.i guess they differ in frequency by a large amount.In Canada and the US the audio FM carrier frequency is 4.5MHz above the video AM carrier frequency. In most of the rest of the world the difference is 5.5MHz, I think. how do they travel after antenna in same single wire?By majic. ;D ;D Umpteen billions of signals can travel in the same wire. My cable TV wire is jammed full of every analog channel, high definition channels, digital channels, pay-per-view and high-speed-internet. They send TV-Guide updates to my box and update its operating program over the same wire as the other stuff. I can transmit orders for pay-per-view from my box on the same cable-TV wire.When I had a TV antenna I also used it for picking-up distant FM stations. At the same time it was receiving many other FM stations and many TV stations.No interference, they all operate at different carrier frequencies. ;D Quote Link to comment Share on other sites More sharing options...
prateeksikka Posted December 11, 2005 Report Share Posted December 11, 2005 hi audioguru!do u mean that the cable wire carries frequency multiplexed audio and video signals?i mean audio at one and video at other frequency but sharing same channel(cable wire) Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 11, 2005 Report Share Posted December 11, 2005 My cable TV wire carries hundreds of analog ordinary TV channels' video and audio carrier frequencies, hundreds of digital TV channels including many that are thousands of miles away that I use for time-shifting, about 40 high-definition channels, about 60 pay-per-view channels including a channel that will play a DVD of just about any movie I want, about 100 audio channels, updates for the program and TV-guide in my digital box and data from me when I order pay-per-view. My digital box even sends data to my cable-TV provider when it isn't feeling well.It isn't multiplexed since each signal has its own frequency.I phone my cable-TV provider each month and threaten to switch to satellite because they are too expensive and I get a nice discount. ;D Quote Link to comment Share on other sites More sharing options...
bloki Posted December 11, 2005 Report Share Posted December 11, 2005 Yes each signal has it's own carrier frequency. Such system is called FDM or Frequency Division Multiplex. Quote Link to comment Share on other sites More sharing options...
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