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HamAntCal version 2.0 (Ham antenna calculator)
HamAntCal version 2.0 has been updated to take advantage of the larger screen size of the iPhone 5
HamAntCal now has metric as well as feet/inches, metric can be sat as the default in the iPhone settings menu
(go to the settings menu and scroll down and look for HamAntCal)
Able to switch between feet/inches and metric on any page
Now able to enter the frequency on any page and have it carry over to all of the other antenna types
(In the settings menu set "global frequency disabled" to "OFF"), If you would like to enter a different frequency for each antenna type, go to HamAntCal in the iPhone settings menu and set "global frequency disabled" to "ON"
Click sounds have also been added to the keypad and can be turned ON or OFF in the settings menu as well.
HamAntCal (Ham Antenna Calculator) will simply and intuitively calculate for you the starting length needed for constructing your antennas. It will calculate the starting length for "Dipole's", "Inverted Vee's", "Vertical's" and has a page for calculating 1/8, 1/4, 1/2, 5/8 and "Full Wave" length using the formula (468/frequency in Mhz) = 1/2 wave in feet and inches, (468/frequency in Mhz) / 2 = 1/4 wave etc….
(For metric the formula used is 142.6464/frequency in Mhz for a half wave)
The "Inverted Vee" calculator also uses this same formula plus a percentage added to the length of the antenna based on the angle of the wires down from horizontal.
I have come across a lot of different and conflicting information for calculating the length of an "Inverted Vee" antenna. Some say subtract 2 to 5 percent based on the angle of the wires. Others say to add a percentage based on the angle of the wires down from horizontal. I decided to test this before releasing this app. First I calculated for a "Dipole" using the "Dipole" calculator. Then I put together a "Dipole" with a support for the center insulator as well as the ends. I measured the resonant frequency with an antenna analyzer. Then I brought the ends down towards 45 degrees from horizontal. As the ends were lowered the resonant frequency increased. This means that the length of the "Inverted Vee" would need to be increased to stay resonant at the same frequency as the dipole.
The "Inverted Vee" calculator has a slider that starts up with an angle of 45 degrees and can be adjusted down to 20 degrees continuously re-calculating as it is moved. This corresponds to about 4.5 to 2 percent added to the length of the "Inverted Vee".
No antenna calculator can give exact results in every case. Much will depend on the wire used, the height above ground, the ground itself, nearby objects, etc…. It's always a good practice to add a little extra wire and then trim up to the desired frequency.
Although I have had good results using this calculator the results are not guaranteed. Always add some extra length and trim the antenna to frequency (it's much easier to trim than it is to add wire to the antenna).
Even though this calculator will calculate from 30 Khz to 500Mhz it is intended for use from 1.8Mhz up to about 54 Mhz. Although it should be close enough for estimating the length of an antenna up to about 148 Mhz .
This app requires iOS 5.0 or newer and has been tested on the iOS 5.0 iPhone simulator and the iPhone 4 with iOS 5.1. Although not written for the iPad it ran fine on the iPad iOS 5.0 simulator (as an iPhone size app).
Please feel free to contact me with suggestions, problems, compliments, ideas for improvements or additions to HamAntCal .
Your ratings are appreciated. Thanks J.G.
New apps coming soon!