IN3LBQ on the Hühnerspiel (Amthorspitze) - photo by IN3OTD

Homemade cheap SMA male calibration kit measurements

The following chapter shows several reference impedances having an SMA male port; note that the SMA connector type used here is not recommended due to its poor build quality. The measurements results are reported for information only; if you need to build an SMA male calkit, see the measurements done using better connectors here.
Some time ago I bought some cheap PCB-mount male SMA, described simply with the part number S01-SPPT4-11BS00 (they can be found on many places on the internet). When they arrived, by simply looking at them it was clear that their quality is far inferior to the nice Molex female SMA I used for the female standards; every connector had some different issues, like dielectric protruding slightly from the body, not cleanly cut, center conductor slightly recessed and so on. For these reasons these connectors are not recommended; for sure I would be very worried at the thought of using them on a professional VNA equipped with precision 3.5 mm connectors!


Simply a bare SMA connector with the center pin trimmed down with a rotary tool the be flush to the dielectric. Also in this case, having a shield or not around the ground pins made no difference, at the frequencies used here.

S01-SPPT4-11BS00_open reference load S01-SPPT4-11BS00_open reflection coefficient

Short (copper disk)

A connector shorted on the back with a small copper disk cut out from thin copper tape; the copper disk just filled the void between the center conductor and the surrounding ground and was then covered with tin-lead solder.

S01-SPPT4-11BS00_short_Cu reference load S01-SPPT4-11BS00_short_Cu reflection coefficient

note that the return loss goes positive at high frequency; as this is not actually possible with a passive load, this likely means there was some issue with the VNA calibration... did not have time to investigate.

50 Ω loads

Also in this case several styles were tried to build a 50 Ω load, using a different number of resistors in parallel. Again, not surprisingly it was found that paralleling a few resistors gives better performances than a single one..
Some of the loads apparently has a low-frequency return loss better than 70 dB; while this number might not be accurate, since it depends a lot on the quality of the initial VNA calibration, it indicates that at low frequency the load is indeed very close to 50 Ω.

Load - 1 x 49.9 ohm

A reference load built using a single Panasonic ERA3AEB49R9V resistor (49.9Ω 0.1 %, 0603 size, 100 mW max).

S01-SPPT4-11BS00_1x49.9ohm reference load S01-SPPT4-11BS00_1x49.9ohm reflection coefficient

Load - 2 x 100 ohm

A reference load built using two Panasonic ERA3AEB101V resistors (100Ω 0.1 %, 0603 size, 100 mW max) in parallel.

S01-SPPT4-11BS00_2x100ohm reference load S01-SPPT4-11BS00_2x100ohm reflection coefficient

Load - 3 x 150 ohm

A reference load built using three Panasonic ERA3AEB151V resistors (150Ω 0.1 %, 0603 size, 100 mW max) in parallel.

S01-SPPT4-11BS00_3x150ohm reference load S01-SPPT4-11BS00_3x150ohm reflection coefficient