Measuring the quality of N adapters by method of Return Loss

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

A04_6650

The adapters A,B,C are laid from left to right in the above photo.

A04_6647

Just after calibration has been completed. No adapter attached.

1_S11_Anritsu_Cal_Load

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

A04_6652A04_6659

Adapter A inserted between test cable and the Cal Load

2_S11_elbow_1

For a 30dB Return Loss, we are good only up to 627MHz

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Adapter B inserted between test cable and the Cal Load

3_S11_elbow_2

For a 30dB Return Loss, we are good up to 1.52GHz

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Adapter C inserted between test cable and the Cal Load

4_S11_ebay_adapter

For a 30dB Return Loss, we are good only up to 641MHz

Conclusion:

Don’t judge an adapter by how nice or shiny it looks. My cruddy old Amphenol adapter is the winner!

Hope you enjoyed reading!

Best regards,

Jeff 9V1As

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