On Fri, Dec 31, 2021 at 06:59 PM, Tomasz Lemiech wrote:
What about connectors for these cables?
Hi Tomasz,
I have standardised on using 'F' connectors on all cables that carry both DC and RF, as this helps prevent accidentally connecting cables with DC onto a receiver input.
Sometimes I use adaptors from F to BNC (or other types) and vice versa, but generally when not carrying DC, I use standard BNC connectors that are available for 75 Ohm CCTV cables such as RG6.
All modern 50 & 75 Ohm BNC connectors are interchangeable, as the pin size has been standardised, and the impedance of the connector (which in this application is not important) is controlled by the amount of dielectric material surrounding the conductors. You may occasionally find old style BNC connectors at surplus and junk sales with a different taper on the pin, and narrower contact fingers on the socket, but these are now becoming increasingly rare and are best avoided.
A few hints if you are using F connectors.
When you make you make up the plug, try to ensure that the dielectric insulation protrudes a short distance past the hole it goes through in the bottom of the connector shell. This helps prevent electrolytic corrosion tracking across the gap and also forms a seal against the edge of the socket receptacle where the spring clips retain the coax inner conductor.
Do not let the inner conductor of the coax protrude too far beyond the open end of the connector shell. If it is excessively long, it can touch the rear of the socket housing and short out the connector, and any DC that may be present.
Two turns of PTFE plumbers tape wound around the screw thread of the F socket, before the plus is screwed onto it will help moisture finding it's way into the connector via the screw thread. It will not affect electrical continuity, as the ridges of the screw thread will cut through the thin PTFE material.
If you join cables outdoors with an in-line back to back socket (bullet), waterproof it with self amalgamating tape and another layer of PVC tape over the top.
Regards,
Martin
