Click here to go to our main page on phase shifters
Click here to go to our first line stretcher example
Click here to go to our second line stretcher example
Click here to go to our page on propagation constant
This page will serve as the main page for different ideas on line stretchers.
Update February 2026, this information came from Marcus:
I recall some really simple models from the 80's that were built like a center conductor sliding into a coaxial tube. And a small locknut to keep them from moving.
These are sold under a variety of names:
Mechanical Phase Shifter
Coaxial Phase Shifter
Trombone Phase Shifter
Coaxial Line Stretcher
There are as many types of line stretchers as there are transmission lines. Liin estretchers are often called trombones, because they accomplish the same purpose, except that the wave that is being delayed is electromagnetic, not audio.
Phase stretchers generally use 50 ohm transmission line modified so that its length can be changed. By lengthening it, more phase is introduced. Note that the phase shift is proportional to frequency (often "ideal" phase shifters try to provide a fixed phase shift with frequency. The phase shift of a line stretcher could be described as "true time delay". Phase stretchers usually provide response down to DC.
Here's an image of an Omni Spectra coaxial line stretcher that covers DC to 18 GHz.
More to come!