Megacycle tape measure.

[NJ Marty]

Here is one I have never seen before. This is a past garage sale purchase and grabbed it today to measure something and said to myself WTF is this.
So what is it used for as I have no clue? These must be a very specific buy that's probably why after many years I have never seen one. They must be somewhat scarce.

 

[The Cobbler]

for calculating antennas I'd say

 

[RC_Dave]

I have never seen one before, but it is for cutting dipole antennas. If you Google "half wave dipole formula" you can make some sense of the tape.

 

[ddawg16]

It gives you a 'physical' way of seeing what is called 'wavelength'. It tells you how far a radio wave will travel in one cycle.

For example, the typical FM signal will travel 10m in one cycle.

In the case of antenna, the best reception for a signal is when the antenna length is multiples of the wavelength....1/4, 1/2, full, etc. Additionally, the antenna distance from the ground plane should also be in the same multiples for best propagation.

There is also a good reason they call it FM....it really means "******* Magic"

 

[NJ Marty]

Thanks so much for the ID on the tape measure, I was stumped.

 

[A_Pmech]

468 / f

Can't pass the General or Extra without it.