right, and for impedance transformers and stubs you have to take that into
account and tune them individually. I do that for my stub filters here.
But this is a case of how long to make it from the antenna to the radio from
what little he told us, so vf is not important.

"Bob Bob" wrote in message
...
Hi Dave

One of the pitfalls is that although a VF of .66 (or .87 for foam) is
common it can vary considerably.

I dont think I have ever seen manufacturers VF specs with a tolerance
listed. In fact I dont think I have ever seen a manufacturers spec
include VF!

Of course it depends on how critical the application is. In my
experience for example 4:1 coaxial baluns on 2m always need to be tuned...

Cheers Bob VK2YQA

Dave wrote:
f


with velocity factor of .66 for generic rg-213 i get 12.988MHz being 2
wavelengths... but why do you care?

here is how to calculate the right length, no fancy measurement equipment
needed.
http://www.qsl.net/w4sat/howlong.htm