tward
Junior Member
More info.... www.Wavelengthcalculator.com if anyone is interested.
Receiver antenna
- Thread starter tward
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wx9dx
Member
DB Gain Of An Antenna:
When you increase DB gain it has to come in the form of focusing the signal more in one direction or another. The shape of the transmitted signal on the ground can be focused on the horizon more with a gain antenna with less radiation over head. The energy that would have been over head with a unity gain antenna is now added out at the horizon with a gain antenna. This is very well brought out in the ARRL Antenna Book!
On several 2.4 GHz receivers they have 2 antennas. One of them sometimes is further away from the receiver and is fed by a length of small coax that some think is just a long antenna, it's not. The other is a simple 1/4 wave 2.4GHz antenna using the ground foil on the circuit board as the ground plane or counterpoise. Some like the Orange series RX use two 1/4 wave antennas, one out one side and one out the front of the circuit both 1/4 wave in length 90 degree apart. I also have a few 2.4GHz receivers where an antenna comes out two sides 180 degrees apart. This to me seems ok but I'd rather have them 90 degrees apart in diversity if possible. But that's me!
You can't have one antenna that can do it all! But you can find one that does ok for most work. You have to use an antenna that is meant to work a certain area, or as better said "from Point A to Point B". For some FPV work a clover leaf antenna is used. This is made to receive the plane of propagation that the signal is in moment to moment, vertical, horizontal or something in between. This is very important on 5.8GHz and 2.4GHz. The signals power is scattered over a very broad frequency range... So a 200Mw Transmitters power is scattered two the wind with small quantities of it in all directions and on a wide RF bandwidth. With very small amounts going towards the receiver. This is why ground mounted directional antennas are often used for Video on Ground Stations or FPV. This allows you to point a high gain antenna towards your aircraft. Also antennas with a right or left hand twist as the signal spirals towards them, earth station or satellite antennas.
For more on this and other antenna information " ARRL Antenna Book":
http://www.arrl.org/shop/search.php?mode=search&page=1
Thanks for the read!
73
Jimmy, ARRL TS, WX9DX
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