Well, even though I had somewhat "OK" performance using the built-in antenna "tuner" on my Kenwood TS-950SDX, the antenna system still wasn't working properly. I dug out the 'spare' SG-230 coupler, and pulled the suspect unit out of the enclosure. I had noticed two 'not-quite-right' things when I first installed it. The PL-259 connector on the input cable didn't look properly installed, and the threaded portion of the output terminal was loose. Since there's a specific warning in the SG-230 manial to use *two* wrenches when tightening the connection, this raised a red flag with me, but (DUH) I went ahead and installed it anyway, hoping for the best, even though I *know* better. Since I had nothing to lose, I pulled the cover off the suspect coupler to give it a look-see. The connection inside the coupler to the output terminal is a threaded brass rod, going through a ceramic standoff, and there's a lug on the end of a wire going to the output of the matching network circuit board.
The nut was 'finger loose' on the inside of the box!
I retightened the nuts on both ends of the brass rod, making sure the wire was nice and tight, and checked the rest of the connections inside the box.
The RF input coax had loose connections, and the power/control leads were also loose in their terminals!
I tightened everything nice and snug, and put the cover back on. I also replaced the PL-259 on the input coax, as I found (as I suspected) that the connector the previous owner had installed had the wrong adapter for the smaller RG-58 coax used for the input lead, and it was very poorly soldered.
Back up the ladder, install the coupler, connect all the cables, and head to The Shack.
It loads up on all bands from 160 Meters (1.8~2.0 MHz) through 10 Meters (28.0~29.7 MHz) with a 1.2:1 VSWR or better. I'm surprised that it loads so well on 160 Meters, as a 24' antenna is waaaay too short for decent performance, but it works, and I'll take it even though I've never operated on that band.
And the receive performance is very nice. I'm blessed with a fairly quiet location here, with local noise levels of about S3 on 40 Meters, less on the higher bands, more on the lower ones.
All I have to do is take a bunch of pix, put the covers back on the two plastic enclosures I'm using to weatherproof the coupler and isolation balun, and neatly dress the cables.