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Like you said, with the flexible version. And this is exactly what to not prefer. Flexible inner conductors made out of multiple wires are not working well on higher frequencies.

And the damping is much less interesting in measurement applications then the reflection. Reflections tend to result in variable signal loss over frequency.

The cable loss is interesting if you build a signal chain for a specific frequency, like in usual transmission systems. Measurement applications have a different focus. So mostly thinner cables have more damping but are also more phase stable and have less reflections on the bench, specifically true for semi rigid and rigid cable. Also it is important that the setup is free of modal waves, will say the diameter of the coaxial system have to be small enough that the waves can't fit in other direction then longitudinal into the the transmission medium.? That's the reason why SMA can only specified to 18GHZ, 3,5mm up to 26,5GHz and 2.92mm up to 40GHz.

RG223 is a nice cable, and I like it because of the easy use on low frequencies with not that bad shielding on this frequencies. But not for measurement applications on higher frequencies. The results are less predictable then with cables especially made for such usage, like the attached Tensolite Workhorse cables for example. Please be aware that also the loss and phase stability is specified by Tensolite. I had to build a special cable some years ago out of such Tensolite cable material, not the armored? version, and it has a solid inner with silver plating, PTFE foam insulation, triple shielding out of three different materials and PTFE outer insulation.

And yes, the SMA connectors on? the not armored version fail very often because of the mechanical stress to the shielding wires on the connector interface. Have to repair them often. But the transmission characteristics up to 18GHz are great!

All this normal SMA connectors are not for measurement applications, the major point is that the inner pin is hold in position by the inner conductor of the cable. This works great for fixed installation and with cable materials where the foam is laminated to the inner conductor to prevent a move of that.

In contrast the connectors for measurement applications are build with a center pin that is hold into place with the insulator parts of the connector. On this connectors cables can be used with a inner conductor that can move inside the insulation. This makes the cable much more robust to bending leading to not that good electrical parameters.

So to bring this two advantages together the cables for microwave measurement applications use a outer tube that restrict the bending radius and the torsion of the cable, inside this tube is a much smaller microwave cable that is perfectly fitted to connectors made for this cable. I would love to have some of this, but they are out of reach for me. A set of two cables for my Anritsu VNA are more expensive then my car. Not possible for hobby use. So I have to deal with the problems that less quality cables brings. For sensitive measurements I use rigid cable, with the knowledge that they are done after some measurements.

But this is all not that problematic with low frequencies, up to 4 GHz I prefer Aircell 7 because the N and the BNC connectors fit well, are very good quality and last for years even it used very often. The connectors can be reused many times. Very good material for common transmission systems and simple measurement applications.

Cables fail more often then anything else. Had some years ago very high priced armored cables from a mayor microwave cable manufacturing on my bench that were useless. I was interested how this can be, disassembled the cables to find out that this 5m long cables had so many movements that the leftovers of the shielding where only dust. So between the outer and the inner insulation was nothing left then aluminum, copper and silver dust. Only the stainless steel protection was left as a ground connection. Not really a coaxial cable anymore...

All the Best,

Isidro

DB1SBI