Many 50 Ohm loads are made with two 100 Ohm smd resistors in parallel. I've seen many loads fail after intensive use, all the sudden they are 100 Ohm when connected. Unconnected 50 Ohm. We solved it by using male/female adapters, so the loads will never be disconnected. By the way, there are adapter without internal thread (male side), you just push them over a female connector. We use the loads in the final product test of RFID readers.
But for calibration of a VNA, I'd use a good quality load without an adapter. Currently I use the cal kit supplied by sdr-kits, based on Rosenberger connectors. They also sell kits based on Amphenol connectors, these loads are junk and will become 100R soon. Never had a problem with the Rosenberger load. Also the load from minicircuits is excellent (ANNEQ-50X+)
Op 21-3-2020 om 05:46 schreef Hern¨¢n Freschi:
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I found the problem. My 50 ohm load was OPEN. I don't know if it can be opened to solder something inside. But tapping it on the table made it work again.
So weird.
