I never use PL259s =junk
I like HNs for HV
There are good uns and bad uns. A good un will handle 3500VDC. I know several who have pushed them to 4500-5000V but I wouldnt try it.
Havent used HN at home, just in industry.
There is also a HV style BNC that can handle some real voltage but I've never been able to buy one. We have one on one of our lightning set ups. A normal BNC dies around 1 KV while the special one doesn't miss a beat.
Thats the MHV series. Rated 2KV at 50 mHz; I use at 2500V DC and audio. The last ones I got up at Deerfield were in a Kings package.
Yup stay away form foam cable for HV. I've never flashed over RG8 or RG11 up to 6 KV or so. Then there is teflon RG393 or RG400 with the new mil names of course.
I use RG 42B and 303 for RF inside of amps but never trusted it at HV due to cold flow. Its also a solid center conductor (silver plated Copperweld?) and hard to manuever.
As I recall the break-down is found to be greater than 80 kV. The big factor here is dc versus radio frequencies; big difference in the insulation physics.
Thanks for that info Tom, I hadnt considered that factor BUT Im not about to find out either!! After I left National Radio I worked for High Voltage Engineering for awhile. Built 100-250KV supplies that stood up to 7' tall for the textile industry. Scary stuff. I like my HV in 4 digit flavors.
Carl
KM1H