"How long will the pole that I buy actually be?" It's a great question but one that people rarely ask. We make it clear that the dimensions are approximate and here is why.
Take a typical 7m pole, made up of 7 sections
- S1 1.22m
- S2 1.10m
- S3 1.10m
- S4 1.10m
- S5 1.10m
- S6 1.00m
- S7 0.84m
= 7.46m
So, a good start, well over 7m. However, when extended, this pole will be shorter because at each of the telescopic joints there is an overlap.
The length of the overlap varies widely. It depends on:
- the accuracy of the pole section diameters
- the thickness of paint applied to the surface
- the effectiveness of the machining to remove the paint
- how hard you pull and twist the pole to lock the sections.
These factors taken together give rise to significant variations in the extended length of all fibreglass telescopic poles. In some cases the variation can be over 5%. For poles that have a large number of sections in order to give a short packed length, and which therefore have a large number of joints contributing to the variation in length, it may be as much as around 10%.
In many cases these variations are not important, however, they can be significant if you want to use the whole length of a pole as a quarter-wave vertical. in such cases it would be prudent to assume that the extended pole will be shorter than the sum total of its section lengths and may well be shorter than the advertised length.
Bear in mind that these poles are not precision items (the cost reflects this). Other sorts of poles are available which are more dimensionally accurate. However, they are generally unsuitable for lightweight portable amateur radio applications. We don't stock them.