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Step 2Cut an antenna wire and attach it
First, let's talk about the antenna length. Every radio transmitter best transmits using an antenna that is optimized in length for the transmitting frequency. This length is related to the wavelength associated with that frequency. To figure the wavelength from any frequency, divide the speed of light by the frequency, and the result is a length. Here's a reference to help you.
The very best antenna for any frequency would be a integer multiple of the wavelength, but this can many times be way too large - an example is this project, utilizing a 433MHz transmitter frequency where the wavelength is .69 meters, or about 27 inches! An acceptable antenna size is 1/2 or 1/4 the wavelength; note that 1/4 of 27.16 inches is about 6.82 inches, and thus within an acceptable range for our needs. Therefore, we will create a final <strong> TOTAL </strong> antenna length of 6.82".
In this particular design, there already is a very small antenna formed on the circuit board (note the length of straight trace running along the front), approximately 1.25" long - this length doesn't really make complete sense as it's approximately 1/20 of a wavelength, so we will add our antenna to the end, to create the correct 1/4 wavelength. To figure the added wire length, we subtract the 1.25" on PCB trace length from the total antenna length needed, we get 5.57" for our added wire. This is the length of the wire we need to cut.
Cut a length of insulated 18 or 20gauge wire to 5.57", as close as you can (the exact length is not critical, as my experiments show that two different designs which vary a bit still work very well). Strip a very small bit of the insulation from one end of wire, perhaps 1/16" left visible.
Note that our antenna is a length of blue 20ga. wire I had. Later, I cover the wire in heatshrink tubing, to protect it and also to make it black, like the rest of the case.
Look to the far left edge of the FS-616 board (near the far '6') and you will find a plated through-hole at the end of the PCB antenna. It is into this hole we will place the stripped end of the copper wire.
Solder the wire in place in this hole, as shown in the picture.
The very best antenna for any frequency would be a integer multiple of the wavelength, but this can many times be way too large - an example is this project, utilizing a 433MHz transmitter frequency where the wavelength is .69 meters, or about 27 inches! An acceptable antenna size is 1/2 or 1/4 the wavelength; note that 1/4 of 27.16 inches is about 6.82 inches, and thus within an acceptable range for our needs. Therefore, we will create a final <strong> TOTAL </strong> antenna length of 6.82".
In this particular design, there already is a very small antenna formed on the circuit board (note the length of straight trace running along the front), approximately 1.25" long - this length doesn't really make complete sense as it's approximately 1/20 of a wavelength, so we will add our antenna to the end, to create the correct 1/4 wavelength. To figure the added wire length, we subtract the 1.25" on PCB trace length from the total antenna length needed, we get 5.57" for our added wire. This is the length of the wire we need to cut.
Cut a length of insulated 18 or 20gauge wire to 5.57", as close as you can (the exact length is not critical, as my experiments show that two different designs which vary a bit still work very well). Strip a very small bit of the insulation from one end of wire, perhaps 1/16" left visible.
Note that our antenna is a length of blue 20ga. wire I had. Later, I cover the wire in heatshrink tubing, to protect it and also to make it black, like the rest of the case.
Look to the far left edge of the FS-616 board (near the far '6') and you will find a plated through-hole at the end of the PCB antenna. It is into this hole we will place the stripped end of the copper wire.
Solder the wire in place in this hole, as shown in the picture.
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In fact, the impedance presented to the RF amplifier will be extremely different for odd number of quarter-waves (low impedance, about 30 ohms) as it will be for even number of quarter waves (high impedance, several thousand ohms). The optimal reception pattern will be different, too, tending toward broadside of the wire direction for odd quarter wavelengths to the end of the wire for even quarter wavelengths.
So the best thing to do is to make it an odd number of quarter wavelengths for maximum power transfer and for optimal reception pattern.
This article in fact recommends a single quarter wavelength -- which is great! But don't fall into the trap of thinking "longer is better" by trying a 1/2 wavelength or even a full wavelength.
http://www.guenthoer.de/bilder/tv-10-1.jpg
http://www.thunderpole.co.uk/angie_fairbanks/right-ang-retractable.gif
.....and then adjust antenna length to fit the need?
antenna mod by blp1979
Which is which and which is better?
Thanks!