alftel
Member level 1
Need community opinion. We have a supplier in China (Voton Machinery, voton.net.cn or rf-connectors.com) who we used in a past to procure SMA and RP-SMA connectors. This time we required SMA pigtails with UFL connector. After receiving cables and attching them to our device we noticed some sort of mis-behavior that could be explained only by impedance mismatch. We crafted UFL socket with soldered 50 Ohm 603 resistor and connected cable to a small antenna analyzer (hard to see on a picture but it is there). To our surprise readings were somewhat off the chart - between 2.4 GHz and 2.5 GHz (100 MHz span) impedance went from 34 Ohm to 61 Ohm, see picture below:
We had another two cables from other inexpensive sources, and they did produce much better results under the same test, even though they are mage with 1.13 cable, and ones that we received from Voton are made with 1.37 cable (supposed to be better). These are readings from another two inexpensive cables:
I wonder if it is usually OK to have this kind of impedance "jumps" and I am paranoiac, or there is definitely a problem with this particular product from this company (again, other two randomly picked cables from our lab bin did produce much better results as seen above). So, this is a cable spec:
Voton cable - SMA connector - UFL connector, 1.37 cable, 100mm long, test frequency 2.4 GHz - 2.5 GHz
Other no-name cable #1 - SMA connector - UFL connector, 1.13 cable, 180mm long, test frequency 2.4 GHz - 2.5 GHz
Other no-name cable #2 - SMA connector - UFL connector, 1.13 cable, 150mm long, test frequency 2.4 GHz - 2.5 GHz
Any opinion or shared experience will be greatly appreciated.
Just to be clear - we did procure SMA and RP-SMA board edge connectors from this source in a past and didn't have any problems (looks like). My understanding is that for 2.4-2.5 GHz terminating cable with 50 Ohm small resistor is suitable setup for a quick and dirty test that supposed to at least show cable behavior in impedance domain vs frequency (at least allows to relatively compare two cables side by side).
We had another two cables from other inexpensive sources, and they did produce much better results under the same test, even though they are mage with 1.13 cable, and ones that we received from Voton are made with 1.37 cable (supposed to be better). These are readings from another two inexpensive cables:
I wonder if it is usually OK to have this kind of impedance "jumps" and I am paranoiac, or there is definitely a problem with this particular product from this company (again, other two randomly picked cables from our lab bin did produce much better results as seen above). So, this is a cable spec:
Voton cable - SMA connector - UFL connector, 1.37 cable, 100mm long, test frequency 2.4 GHz - 2.5 GHz
Other no-name cable #1 - SMA connector - UFL connector, 1.13 cable, 180mm long, test frequency 2.4 GHz - 2.5 GHz
Other no-name cable #2 - SMA connector - UFL connector, 1.13 cable, 150mm long, test frequency 2.4 GHz - 2.5 GHz
Any opinion or shared experience will be greatly appreciated.
--- Updated ---
Just to be clear - we did procure SMA and RP-SMA board edge connectors from this source in a past and didn't have any problems (looks like). My understanding is that for 2.4-2.5 GHz terminating cable with 50 Ohm small resistor is suitable setup for a quick and dirty test that supposed to at least show cable behavior in impedance domain vs frequency (at least allows to relatively compare two cables side by side).
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