MCX to SMA Adapter

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Bob Marston

Jul 29, 2021, 6:56:24 PM7/29/21
to sark110
I recently purchased an adapter for my SARK-110 from Max-Gain-Systems. It's a Male MCX to Female SMA Adapter. When I go to attach the adapter to the Analyzer it does not mate. I am firm with the application but no success. I backed off fearing that if I applied too much force I would damage the connector or worse. My questions are the connector on the analyzer is a Female MCX right ? This problem is a MOTO (Master of the Obvious) and obviously I am missing something. Is their anyone that could enlighten me ?

73s and thanks for your attention


Aug 2, 2021, 12:45:36 PM8/2/21

Hello Bob,


Do you have a link to the information from the vendor?

The SARK110 requires a MCX straight male plug. One possible cause is that it is a reverse polarity (RP) plug, or that the connector from this vendor has some deviation so that does not mate correctly.



Melchor EA4FRB

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Bob Marston

Aug 2, 2021, 1:19:02 PM8/2/21

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Aug 2, 2021, 3:38:29 PM8/2/21

Hi Bob,


Thank you for the link. What I can see from the pics in the information page is that the MCX plug part is compatible (it is not reverse polarity), but there is no detailed datasheet provided. Perhaps, the different shape (double vs single chamfer) at the plug stop makes the difference; see pics below for comparison.


Unfortunately, I don’t have a similar adapter for testing, so I cannot provide you an assessment now. I can try to source it, but it can take some time.


Figure 1, Supplied adaptor by Seeed Studio

Figure 2, Max-Gain Systems

Best regards,


John G3PQA

Aug 2, 2021, 9:20:49 PM8/2/21
Hi Bob,
I have used several Sark-110 over the last few years and occasionally have come across this problem when
a) the adaptor or plug is out of specification or
b) has a ridge immediately after the plug and cannot plug in properly past the Sark-110 case or
c) is a right angle plug which does not reach in the case far enough to fix properly because the socket is recessed slightly in the case (which is not normally a problem with straight MCX plugs)

There is the possibility that your Sark MCX socket is out of specification, but if the pigtail that was supplied with the device fits then this is seems unlikely, particularly as the 110 presumably was tested before supply. I have replaced my MCX socket once because the inner partially broke but the fit was the same.

For HF field use I do not normally use the supplied pigtail myself as the cable is rather stiff and makes the plug flex slightly in the socket when extended. To minimise strain on the socket I use a flexible RG174 test lead about 800mm long with a straight MCX one end and BNC female the other end, with new calibration of course.

A few years ago someone designed a 3D printed plastic adaptor holding a SMA female adaptor, which seated over the end of the Sark. This is fixed using two slightly longer case screws.

Bob Marston

Aug 3, 2021, 12:19:19 PM8/3/21
Hi John

Thanks for taking the time to type this up. What you expressed is my suspicion also. Now for the piece I omitted in my original communication. I have purchased a half dozen Adapter Cables from a different vendor. All of the cables feature MCX male connectors on one end and all of them work fine. What the problem feels like to me is the Dielectric Ring of the Male plug is pushing against some part of the Female plug that it should be slipping over. What I have done is order a second adapter plug to see if I have the same problem. I will keep the List informed as the situation develops.

73s All


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