1. Home
  2. Electronic Components
  3. BNC for use at 11GHz ?

BNC for use at 11GHz ?

Hi All,

For years, I have been gently preaching that BNCs are only any use up to 1GHz and if you want to go any higher use TNC for a similar footprint.

Recently I tripped over

formatting link
indicating that their BNCs are OK up to 11GHz.

Any ideas where the 1GHz limit for BNCs might have arisen from ? I am sure I have seen it numerous times in Ham Radio publications.

Engaging brain (don't be alarmed, only for a minute), the main difference between BNC and TNC is the outside thread rather than the bayonet method of attachment. "Forward" current is carried by the centre pin. Impedance is set by diameters and qualities of the pin and dielectric in the part. Return RF current is carried by the fingering inside the male and it's contact with the barrel of the female.

If this is true for BNC and TNC, why would any performance difference have ever been quoted ?

Finally, does anyone have a link to the MIL spec / drawings for the fabrication of BNCs and TNCs ?

Regards,

Mark.

Reply to
MarkAren
Loading thread data ...

They are playing fast and loose with the 11GHz figure. If you read down in the actual specs they say that they only guarantee VSWR's below

1:1.3 (or 1:1.35) up to 4GHz.

I mean, a quarter-inch phone plug will let some signal through at some horrendous SWR at 11GHz :-).

The limit depends on what SWR you're willing to take, and that depends on power levels (transmitters) or noise figures (receivers) and cables and gain budgets and a bunch of other things. Anybody telling you a single number for a limit is putting a lot of stuff under the rug.

It's also true that if you do not do "officiial" crimps that your SWR's are probably going to be way higher than the numbers on the spec sheets. I think the 1GHz number is pessimistic for official crimps but probably realistic for typical ham crimps. It's hopelessly optimistic for say twist-on BNC's.

And note that many manufacturers carry cheapo grade connectors (e.g. Amphenol RFX) as well as sometimes premium grade connectors that do worse or better at higher GHz than the usual stuff at very different price points.

Tim.

Reply to
Tim Shoppa

I think it was actually for the cable, rather than for the plug. Normally BNC's, use RG58, and the 10' (3m) -3dB point for this is normally about

1GHz. Like most 'rules of thumb', it misses a lot...

Best Wishes

Reply to
Roger Hamlett

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.