Designing a Mobile Whip Antenna at 30MHZ

[ZunairaF]

Hi all. I am preparing for a job test, and I came across the question to determine the length of the mobile whip antenna at 30MHz frequency. As per my calculations, the answer should be 2.5m. The one stated in the answer book is 0.45m. I will be grateful if anyone can help.

 

[betwixt]

30MHz = 10m
So a quarter wave vertical above a ground plane would be 10m / 4 = 2.5m.

That makes you correct using theory alone but in practice 2.5m would be too long for handheld or vehicle mounted antennas. Consider driving under bridges for example. Most whips are made shorter by adding a 'loading coil' near the base to make them physically shorter while still having the same electrical length.

Brian.