BNC interchangeable? - UK Vintage Radio Repair and Restoration Discussion Forum

neutronic · 27th Feb 2014, 3:03 pm

As the Dutch Wikipedia claims interchanging RG58 with RG59 (50 Omms to 75 Ohms)would give irretrievable damage,it makes me worry about.
They suggest that the dimensions differ too much.

Is this true ?
Swapping them is something I do all the time.
Half of the test equipment is Philips (75 Ohm) and the other half US (50 Ohms)
Only used in AM and FM sets.
The cables are short (max. 1 meter),but these are also mixed.

Jard N.

Restoration73 · 27th Feb 2014, 4:34 pm

I have not found that ; RG58=UR76, RG59=UR70 british cable types.
The only thing you might damage is a 75 ohm bnc socket, if you try to insert a 50 ohm
plug, which has a larger pin

27th Feb 2014, 4:40 pm

Quote:

The only thing you might damage is a 75 ohm bnc socket, if you try to insert a 50 ohm
plug, which has a larger pin

That is for N type connectors, BNCs have the same sized pin. Cables below a small fraction of a wavelength long won't affect much, 1m at 'FM' (100MHz, 3M wavelength) would make a difference though. 75ohm BNCs have a lot less plastic in them, easy to tell apart, not so easy to identify alone!

Malcolm G6ANZ · 27th Feb 2014, 4:49 pm

I have always understood that 50 and 75 can be put together without any mechanical damage. The problems occur in the mismatch of impedances.Ref the article:

http://www.milestek.com/blog/index.p...ors-explained/

Malcolm

Biggles · 27th Feb 2014, 5:30 pm

I have always understood the 75 ohm BNC had a fatter pin and would therefore cause damage to the 50 ohm socket. In fact we had a case of a 50 ohm socket on a transmitter duplexer which had exactly that type of problem. The pin apparently is fatter nearer the cable entry end i.e. more conical and wider where it enters the plastic insulation. But I may stand to be corrected.....
Alan.

k_yller · 27th Feb 2014, 6:10 pm

IMVHO one difference exists, because of cable different thickness only, Russians have bit different design of this kind of coupling.

neutronic · 27th Feb 2014, 7:45 pm

Something like this?
Picture:see attachement

Besides,this afternoon while I was searching at Google,I even found a link to this site:
https://www.vintage-radio.net/forum/...ad.php?t=47357

Jard N

Radio Wrangler · 27th Feb 2014, 9:44 pm

BNC does 75/50 Ohm variants by removing dielectric

N does 75/50 ohm variants by changing the diameter of the centre pin (and 75 ohm females are ruined by 50 Ohm males)

SMB and SMC do 75 and 50 Ohm variants with the same centre pin, but different outside diameters.

So all three games have been played.

David

emeritus · 27th Feb 2014, 10:10 pm

I just checked some of my 1980's electronics catalogues. They explicitly state that (for Radiall and Greenpar at least) 75 and 50 Ohm BNC connectors are mechanically interchangeable, but the corresponding N types are not.

neutronic · 27th Feb 2014, 11:09 pm

Luckily it´s very obvious to see for N-types.

N connector is a threaded RF connector and commonly is used to join with coaxial cable. N connector was invented in 1940’s and comes in 50 ohm and 75 ohm impedance.
The 50 ohm N connector is widely used in the infrastructure of wireless base station and cellular base station, and the working frequency normally is from hundred MHz to 5.8GHz. The 75 ohm N connector can work up to 1.5GHz, and is primarily used in the infrastructure of cable TV systems.
Mechanical Feature:
N male
Inner thread of 5/8-24UNEF-2B, Inner diameter is from 14.732mm to 14.986mm
An air gap between centre and outer contacts
Outer diameter range is 19.5mm ~ 21.0mm
Silicon Rubber O-ring inside
Male centre contact has dia. 1.60mm ~ 1.68mm for 50 ohm N male ; dia. 0.87mm ~ 0.91mm for 75 ohm N male

Jard N.

Mikebay · 4th Mar 2014, 12:11 pm

One other difference I have found in the past is that the o.d. of RG59 cable is v. slightly greater than RG58. This makes the fitting of the clamp section of the plug/socket difficult to impossible.
Just my penny's worth from experience

FrankB · 10th Mar 2014, 12:19 am

I have found the only difference in the BNC connectors for RG 58 and 59 to be the outside diameter of the cable itself.
I have yet to see a center pin size difference here in the USA.
On most of my test equipment I do try to use the factory specified cable, but in reality have found little difference between the two types for test leads. But on the capacitor tester it did make a measurable difference, as it should.

On PL259's, it's the insert that goes into the back of the connector that is a different size. One each of 3 different sizes for RG58, 58X, and 59.

27th Feb 2014, 3:03 pm	#1
neutronic Pentode Join Date: Oct 2009 Location: Bergen, North Holland, The Netherlands Posts: 180	BNC interchangeable? As the Dutch Wikipedia claims interchanging RG58 with RG59 (50 Omms to 75 Ohms)would give irretrievable damage,it makes me worry about. They suggest that the dimensions differ too much. Is this true ? Swapping them is something I do all the time. Half of the test equipment is Philips (75 Ohm) and the other half US (50 Ohms) Only used in AM and FM sets. The cables are short (max. 1 meter),but these are also mixed. Jard N.

27th Feb 2014, 4:34 pm	#2
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: BNC interchangeable? I have not found that ; RG58=UR76, RG59=UR70 british cable types. The only thing you might damage is a 75 ohm bnc socket, if you try to insert a 50 ohm plug, which has a larger pin

27th Feb 2014, 4:49 pm	#4
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,042	Re: BNC interchangeable? I have always understood that 50 and 75 can be put together without any mechanical damage. The problems occur in the mismatch of impedances.Ref the article: http://www.milestek.com/blog/index.p...ors-explained/ Malcolm

27th Feb 2014, 5:30 pm	#5
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: BNC interchangeable? I have always understood the 75 ohm BNC had a fatter pin and would therefore cause damage to the 50 ohm socket. In fact we had a case of a 50 ohm socket on a transmitter duplexer which had exactly that type of problem. The pin apparently is fatter nearer the cable entry end i.e. more conical and wider where it enters the plastic insulation. But I may stand to be corrected..... Alan.

27th Feb 2014, 6:10 pm	#6
k_yller Pentode Join Date: Jan 2014 Location: Huddersfield, West Yorkshire, UK. Posts: 129	Re: BNC interchangeable? IMVHO one difference exists, because of cable different thickness only, Russians have bit different design of this kind of coupling.

27th Feb 2014, 7:45 pm	#7
neutronic Pentode Join Date: Oct 2009 Location: Bergen, North Holland, The Netherlands Posts: 180	Re: BNC interchangeable? Something like this? Picture:see attachement Besides,this afternoon while I was searching at Google,I even found a link to this site: https://www.vintage-radio.net/forum/...ad.php?t=47357 Jard N Attached Thumbnails

27th Feb 2014, 9:44 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: BNC interchangeable? BNC does 75/50 Ohm variants by removing dielectric N does 75/50 ohm variants by changing the diameter of the centre pin (and 75 ohm females are ruined by 50 Ohm males) SMB and SMC do 75 and 50 Ohm variants with the same centre pin, but different outside diameters. So all three games have been played. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

27th Feb 2014, 10:10 pm	#9
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,346	Re: BNC interchangeable? I just checked some of my 1980's electronics catalogues. They explicitly state that (for Radiall and Greenpar at least) 75 and 50 Ohm BNC connectors are mechanically interchangeable, but the corresponding N types are not.

27th Feb 2014, 11:09 pm	#10
neutronic Pentode Join Date: Oct 2009 Location: Bergen, North Holland, The Netherlands Posts: 180	Re: BNC interchangeable? Luckily it´s very obvious to see for N-types. N connector is a threaded RF connector and commonly is used to join with coaxial cable. N connector was invented in 1940’s and comes in 50 ohm and 75 ohm impedance. The 50 ohm N connector is widely used in the infrastructure of wireless base station and cellular base station, and the working frequency normally is from hundred MHz to 5.8GHz. The 75 ohm N connector can work up to 1.5GHz, and is primarily used in the infrastructure of cable TV systems. Mechanical Feature: N male Inner thread of 5/8-24UNEF-2B, Inner diameter is from 14.732mm to 14.986mm An air gap between centre and outer contacts Outer diameter range is 19.5mm ~ 21.0mm Silicon Rubber O-ring inside Male centre contact has dia. 1.60mm ~ 1.68mm for 50 ohm N male ; dia. 0.87mm ~ 0.91mm for 75 ohm N male Jard N.

4th Mar 2014, 12:11 pm	#11
Mikebay Rest in Peace Join Date: Nov 2006 Location: Leominster, Herefordshire Posts: 174	Re: BNC interchangeable? One other difference I have found in the past is that the o.d. of RG59 cable is v. slightly greater than RG58. This makes the fitting of the clamp section of the plug/socket difficult to impossible. Just my penny's worth from experience

10th Mar 2014, 12:19 am	#12
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: BNC interchangeable? I have found the only difference in the BNC connectors for RG 58 and 59 to be the outside diameter of the cable itself. I have yet to see a center pin size difference here in the USA. On most of my test equipment I do try to use the factory specified cable, but in reality have found little difference between the two types for test leads. But on the capacitor tester it did make a measurable difference, as it should. On PL259's, it's the insert that goes into the back of the connector that is a different size. One each of 3 different sizes for RG58, 58X, and 59.