Ever wondered how good (or bad) your RF adapters are?
I asked myself this question, and concluded that an RF adapter should change the impedance as little as possible.
Here is the experimental method I adopted.
1. Calibrate the Anritsu S331E Sitemaster at the end of a phase stable test cable using its OSL Calibrator (Type OSLN50-1)
2. Make a record of the Return Loss with the 50 ohm calibration load attached.
3. Now interpose the adapter-under-test between the end of the test cable and the Calibration Load.
4. Make a new record to see how the Return Loss compares with that of Step 2.
For the purpose of this evaluation, I picked 3 adapters:
Adapter A: A shiny 90 degree N-type M-F adapter of unknown pedigree
Adapter B: A cruddy looking Amphenol 90 degree N-type M-F adapter
Adapter C: A straight N-type M-F adapter bought from Ebay for a few dollars
The adapters A,B,C are laid from left to right in the above photo.
Just after calibration has been completed. No adapter attached.
After calibration (Step 2), you can see that the Return Loss is what the Anritsu manual tells us, viz better than 42dB for all frequencies below 3GHz
Adapter A inserted between test cable and the Cal Load
For a 30dB Return Loss, we are good only up to 627MHz
Adapter B inserted between test cable and the Cal Load
For a 30dB Return Loss, we are good up to 1.52GHz
Adapter C inserted between test cable and the Cal Load
For a 30dB Return Loss, we are good only up to 641MHz
Don’t judge an adapter by how nice or shiny it looks. My cruddy old Amphenol adapter is the winner!
Hope you enjoyed reading!