i finally got some APC-7/SMA-F connectors from China. One has problems with the threaded sleeve not extending. Both appear to have been assembled using something similar to Loctite, so I'm not able to fix the sleeve issue.
For comparison I have some new Weinschel APC-7/SMA-F adapters.
from the bottom:
Chinese RG402 SMA-M to SMA-M open
with Wienschel adapter open
with HP 909A APC-7 50 ohm load.
The vertical lines on the lower two traces show the plane of the open. Obviously the adapter is better than the cable termination.
The Chinese APC-7/SMA-F are clearly not as good. Though they look as if they would be usable on an 8753x up to 6 GHz.
The traces are as the Weinschel case, just different APC-7/SMA-F adapter.
I got 4 Weinschels for $100 and 2 of the Chinese for $30.
It's a bit harder to grasp what is going on with the Chinese stuff as a capacitive bump appears when the load is connected which is not there when it is open. The fingers on the center conductor stick out farther than on the 909A loads or the Weinschel adapters.
Once I get all the cabling for my 8510C I'll update the TDR displays with VNA sweeps.
Edit: I just noticed that the photo for the Chinese adapter has the bottom trace at 10 mV/div. The other traces are 20 mV/div. The capacitive reflection is about 0.04 for both the SMA-M on the RG402 cable and the -0.04 for the adapter. Not great, but usable below 6 GHz.
I was able to disassemble the adapter with the non-working sleeve and fix it. They appear to have been epoxied. So a hot air gun should simplify taking them apart.
These are obviously not a good deal relative to the Weinschels, but you might have to wait a long time to get the sort of deal I found.
Addendum:
I just measured the rise time going through the two Chinese AP-7/SMA-F adapters and two Weinschels and both have a thru rise time of 35 ps. With a single20" RG402 jumper I measure 30 ps.
Reg