Telescopic Antenna - Adjusting length to match frequency

[andrewsfm]

I bought a telescopic Nagoya NA-767 antenna.
It has 3 sections as shown in the image.
The telescopic section is a total of 87cm long when fully extended.

I have a mobile handheld radio.

I will use an antenna length calculator website to figure out what length I need according to the frequency I'm on, but I have a few questions...

A. What length should I be using for the best gain?
1/4, 3/8, 1/2, 5/8?

B. What sections should be included in the antenna length calculation when extended?
Only 1, or 2 as well?

C. How does the load coil affect the length calculations?
Does it add a defined amount of invisible length?

 

[andrewsfm]

Okay... Does anyone know a good radio message board I could post this question on and get some help with it?

 

[kc5uta]

Only thing I can think of is to borrow or use an antenna analyzer, or SWR meter and try it out. Watch the impedence and SWR at the same time. 3/8, 1/2, 5/8 wave antennas are difficult to match in the first place and require some extra care. Unless that antenna is designed to do those variations, I doubt it will tune. Sorry to not be of more help. KC5UTA....Dave