Quick video comparing mobile antenna whip lengths

[M0GVZ]

I know I always bleat on about it being all about getting wire in the air and on QRZ someone asked a question about using longer whips on the Little Tarheel 2.

As I have one and a collection of whips I did a little experiment on the way home from my radio club meet. I compare the stock 32" whip, a 64" one that I use all the time taken from a Sirio Hypower 4000 and a 10ft 6in one. Unfortunately the 10ft one flaps about like you wouldn't believe because its far too thin to support itself but it gives you an idea.

Going from the 32" to 76" one, doubling the length, gave a 6dB increase - that's four times the signal strength. As gain is reciprocal, any gain on the RX also applies to TX. So if you're using one of those shitty 3-4ft CB antennas, changing to a 6ft one or a 102" tank whip and running just 25W into it would give you a signal strength the same or more than running 100W into the shorty.

 

[fourstringburn]

Nice video.

You should mention that when using longer whips, you can start losing the upper bands one by one the longer the whip gets. This does improve performance on the lower bands as your video shows.

If your antenna setup can stand the wind loading, capacity hats is the better way to go to get the longer whip equivalent while maintaining a manageable antenna height. This will improve antenna performance even more by using capacitance to counteract and reduce the inductive coil losses with less coil turns needed to match the antenna to a specific frequency.

Cap hats also raise the RF currents above the coil to the top of the antenna since a cap hat is true top loading.

For the Little Tarheel models, cap-hats aren't recommended by the manufacture since these are small antennas with a 1 inch diameter coil. However, I used one on a Little Tarheel and had no problems. The cap-hat needs to be lightweight and no more than a 30 inch radius to keep the weight and wind loading from damaging the antenna coil.

Also just like using longer whips, the larger the cap-hat radius, the upper bands will be lost. A 30 inch radius kept 10 meters with the antenna nearly topped out but I lost 6 meters. So in essence this is like using an 8 ft. whip on the antenna but the capacity hat system is only 2 ft. tall!

I used the DX engineering caphat system on that antenna and now on my larger Model 100A Tarheel.