【實用工具app】HamAntCal|最夯免費app-綠色工廠好玩App

HamAntCal Version 2.0 (Ham Antenna Calculator) will simply and intuitively calculate for you the starting length needed for constructing your antennas in feet/inches or in meters. 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 142.6464/freq 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.

In this update:

▪HamAntCal has been updated to take advantage of the larger screen size of the the new iphone5

▪HamAntCal now has metric as well as feet/inches

Metric can be set as the default in the iPhone settings menu

(go to the iPhone settings menu scroll down and look for HamAntCal)

▪Able to switch between feet/inches and metric output on any page

▪Enter frequency on any antenna type and have it carry over to all other antenna types

("global frequency disabled" set to "OFF" in the settings menu)

▪Enter different frequency for each antenna type

(global frequency disabled set to "ON" in the settings menu)

▪Click sounds have been added for keypad entry and auto calculation

(able to turn sounds ON and OFF in the settings menu)

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▪ 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.

▪ Please be safe while building your antennas. Always use the proper safety equipment. Never build your antenna where it can come in contact with power lines, this includes the supports as well as the antenna itself and feed lines. BE SAFE!

▪ 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). Please feel free to contact me with suggestions, problems, compliments, ideas for improvements or additions to HamAntCal . Your ratings are appreciated. Thanks J.G.

▪ 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 iPhone 5, iPhone 4S, iphone4. Although not written for the iPad it ran fine on the iPad iOS 5.0 simulator and the ipad1 (as an iPhone size app).