Download GW3LTX Amateur Radio Site Files.
"Whipcal" if you're into /M operation.
This program will make the manufacture of a mobile whip aerial quite easy.
First select the whip aerial you will be using. Next find something to use as a former for the coil, old CB whips can often be adapted but I use PVC water pipe with suitable end plugs or caps. Remember the whole aerial has to be able to withstand quite high windage when you are mobile. Having got your materials measure them and enter the data into the program, it will tell you how many turns you need depending on the diameter of wire you decide to use. The type of vehicle, the height above ground and your mounting arrangement will affect the resonance, so put a few more terns on than needed to enable easier trimming on the vehicle.
"Whipmatch" to efficiently match your new /M aerial.
Having manufactured your mobile whip aerial and trimmed it to resonance on the vehicle use Whipmatch to calculate the shunt capacitor needed for a perfect match. You will need to accurately measure the Standing Wave Ratio using a good SWR bridge or an aerial analyser. Enter the result into the program and it will calculate the shunt capacitor for you.
"HelixCalc" to design helical aerials for Satellite Work.
Based on the formulae for designing a UHF helix the program "HelixCalc.zip" takes all the hard work out of designing a directional helical aerial for the UHF or SHF bands. Just run it and enter the frequency and the number of turns you require.