The first thing you should consider when attempting building an antenna
do i have the proper materials, and can i take my time to do it right ?
The higher the frequency the more important it becomes to get the measurements exact, at 900mhz (a low frequency) it is not as critical when you get up to the
5.8 ghz "5800 mhz" if your off by 1mm it can shift the antenna from 5800 to 5300 making it loose all distance and reliability. so when making the 5.8 ghz antennas double and triple check your measurements. When making the 5.8 ghz antennas wire size is also critical, if you use too thick diameter wire the antenna will be what is called Wide band means it will pickup noise from lower frequency's and also distorts your measurements , so if you make a 5.8ghz antenna from letts say 14 guage house conduit wire, your antenna will no longer be "selective" to the 5.6-5.9 ghz range , it can range from 4.1 to 6.9 ghz or lower. this means your antenna will pick up every thing in between including your frequency , dont get me wrong it will still work but it just wont be that good, especially at distance. If you want to paint your antenna you can but DONT paint any of the copper/brass surfaces, it might make it look cool but it can really screw up the end result, some paint on the center former is ok but do it before you install the wire & ground plane the reason is the paint will also affect the antennas ability to receive Video & Audio signals especially...Continue Reading
For all of the users of 2.4 ghz systems, that don't specifically have an rssi out, there is a easy way, most of this info is from Old man mike's posts, (requires you to remove the case from rx, also receiver has to have LED lights that react to signal loss, ie when the rx is on and the tx is off you get a solid red light, and when you turn on the tx the rx light switches to a solid green light, and when you put your tx in the microwave with the door closed and take the powered up rx and start waking away from the tx , the green and red lights will start to flash,"indicating signal loss" and eventually go to solid red. what you do is remove the case from the receiver you want to get rssi from , then locate the LED lights, using a multi meter hook up the ground to one of the ground pins,"or other ground on the tx", then with the tx and rx both powered up check the voltage on the led's then turn off the tx and test the voltage , one of the two led's will have "high or low" voltage when tx is on and "low or high" voltage when the tx is off, this is what you will use for rssi, but it is just a pulse sent to the led so it has to be converted to an analog dc voltage, simply use a 100k resistor from the + side of your chosen led, "so you barley draw any voltage from the rx" and use a capacitor to hold the charge from the rx, the larger the capacitor the slower rssi will change in osd, the capacitor value will usually be between 2uf-22uf, i use 22uf on the futaba and frysky rx's
just a basic break down, a camera with video out only needs 3 wires 2 for power usually black and read, the third is the video out & it shares the ground with the power, transmitters also need the red and black wires for power they have a video In pin or connection that is where the yellow wire is connected, so now you have a camera and transmitter hooked up, now you need to power the receiver (make sure both the transmitter and receiver are on the same Chanel) the receiver will have the same black and red for power, and a video out usually with a nice rca jack for easy hook up to goggles and/or dvr and/or a video screen (like the dvd players in cars) when every thing is powered on and the transmitter and receiver are on the same channel you will see the transmitted video from the camera hooked up to the transmitter on the receiver side on what ever you have hooked up to view the image