[TowerTalk] real world formula for the length of a quarter wave transmission line

[Jim Brown]

And don't forget that Vf varies a bit with frequency (it's slightly 
lower at lower frquencies). The difference is small, but enough that you 
want to carefully tune the stub at the frequency that you want it to 
reject.  The difference is greatest on the lower ham bands, enough that 
you won't get as much suppression as you expect because it's a bit off 
frequency, and not big enough to matter above 20M.

More about this in my Coax and Stubs tutorial, previously cited.

73, Jim K9YC

On 2/13/2013 9:07 PM, Jim Lux wrote:

> So, for a top of 75meters 1/4 wave, it would be 246*VF/4 or 61.5*VF