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

[Jim Lux]

On 2/13/13 9:16 PM, Jim Brown wrote:
> 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
>
> __

I think the OP was looking for a impedance transformer, and for that 
application, I think small errors in length won't have a big effect. 
Say you were using 1/4 wavelength of 75 ohm line to transform 50 ohms to 
112.5 ohms.. If the line were 7/32 wavelength, would it be that much 
different?