What type of coax connector? - UK Vintage Radio Repair and Restoration Discussion Forum

jim_jobe · 20th Dec 2014, 4:11 pm

Can anyone enlighten me as to what type of coax socket this is please? I want to buy some but don't know what to ask for.

paulsherwin · 20th Dec 2014, 4:26 pm

Looks like BNC: http://en.wikipedia.org/wiki/BNC_connector

Nuvistor · 20th Dec 2014, 4:28 pm

Looks like a BNC to me.
http://en.m.wikipedia.org/wiki/BNC_connector

Edit. cross post.

20th Dec 2014, 4:39 pm

It is indeed a BNC to me it looks like a 75ohm one. That won't matter 50ohm ones fit without damage (unlike the N type). What is it on?

Nicklyons2 · 20th Dec 2014, 4:46 pm

As Merlin intimates you really should use the correct impedance version - video is almost always 75 Ohm, RF stuff, carrier systems PMR radio aerials etc 50. If you only want 1 or 2 I may be able to sort some out for you. PM me if interested, Nick

Radio Wrangler · 20th Dec 2014, 5:14 pm

I'll disagree with the above. I think it looks more like a 50 Ohm BNC female.

75 Ohm ones have the PTFE insulation cut back further, 50 Ohm ones have the PTFE surrounding the whole of the female centre contact.

I designed telecomms test gear for some years and 75 Ohms was the norm, so I've seen a lot of BNC and N-types of both impedances. BNCs are fairly innocuous, but 75 N-type females were ruined if anyone attached a 50 Ohm male.

David

jim_jobe · 20th Dec 2014, 6:18 pm

Cheers gents
That one is on a homebrew sig. gen. I want a couple more to go with a frequency meter and another home brew sig.gen. so that I can use them with some nice oscilloscope probes that I have. I'll pm you about your kind offer Nick

timewave · 20th Dec 2014, 6:22 pm

Yes, definately 50 ohm BNC female. I see them just about everyday both at work and at home.

John G4IJD

G6Tanuki · 20th Dec 2014, 6:36 pm

I had experience with tens of thousands of 75-Ohm BNC connectors - they were the type specified for use with 93-Ohm RG62A/U coax used to feed IBM "3270" displays http://www-01.ibm.com/support/knowle...61.htm?lang=en and their successors to 3214/3174 'cluster controllers' http://www.redbooks.ibm.com/Redbooks...l?OpenDocument

IBM never bothered about the impedance mismatch from using 75-Ohm BNC connectors with 93-Ohm coax. I've always had a similarly permissive approach to mating 50- and 75-Ohm versions for generic RF applications below a couple of hundred MHz.

Station X · 20th Dec 2014, 8:01 pm

Isn't there a problem with different diameter centre pins?

G6Tanuki · 20th Dec 2014, 8:12 pm

Yes but you generally get away with it!

emeritus · 21st Dec 2014, 1:24 am

I think it is the type N connectors where 50 and 75 ohm types should not be mated. My old Suhner catalogue says that 75 and 50 ohm BNC connectors can be mated without damage.

Biggles · 21st Dec 2014, 1:30 am

Years ago we had a problem with a poor contact on a BNC female connector mounted on a transmitter duplexer and we put it down to someone using a 75 ohm BNC plug with a fatter pin forcing the contacts too far apart. A bit of careful realignment of the centre contact leafs cured the problem. I agree with Station X that you should only use the correct impedance connector plug/socket combination with BNCs.
Alan.

21st Dec 2014, 2:08 pm

Quote:

Originally Posted by Radio Wrangler

I'll disagree with the above. I think it looks more like a 50 Ohm BNC female.

I stand corrected.

20th Dec 2014, 4:11 pm	#1
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	What type of coax connector? Can anyone enlighten me as to what type of coax socket this is please? I want to buy some but don't know what to ask for. Attached Thumbnails

20th Dec 2014, 4:26 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: What type of coax? Looks like BNC: http://en.wikipedia.org/wiki/BNC_connector

20th Dec 2014, 4:28 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: What type of coax? Looks like a BNC to me. http://en.m.wikipedia.org/wiki/BNC_connector Edit. cross post.

20th Dec 2014, 4:39 pm	#4
Guest Guest Posts: n/a	Re: What type of coax? It is indeed a BNC to me it looks like a 75ohm one. That won't matter 50ohm ones fit without damage (unlike the N type). What is it on?

20th Dec 2014, 4:46 pm	#5
Nicklyons2 Octode Join Date: Jan 2013 Location: Barnsley, South Yorkshire, UK. Posts: 1,517	Re: What type of coax connector? As Merlin intimates you really should use the correct impedance version - video is almost always 75 Ohm, RF stuff, carrier systems PMR radio aerials etc 50. If you only want 1 or 2 I may be able to sort some out for you. PM me if interested, Nick

20th Dec 2014, 5:14 pm	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: What type of coax connector? I'll disagree with the above. I think it looks more like a 50 Ohm BNC female. 75 Ohm ones have the PTFE insulation cut back further, 50 Ohm ones have the PTFE surrounding the whole of the female centre contact. I designed telecomms test gear for some years and 75 Ohms was the norm, so I've seen a lot of BNC and N-types of both impedances. BNCs are fairly innocuous, but 75 N-type females were ruined if anyone attached a 50 Ohm male. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

20th Dec 2014, 6:18 pm	#7
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: What type of coax connector? Cheers gents That one is on a homebrew sig. gen. I want a couple more to go with a frequency meter and another home brew sig.gen. so that I can use them with some nice oscilloscope probes that I have. I'll pm you about your kind offer Nick

20th Dec 2014, 6:22 pm	#8
timewave Pentode Join Date: Apr 2006 Location: Clitheroe, Lancashire, UK. Posts: 173	Re: What type of coax connector? Yes, definately 50 ohm BNC female. I see them just about everyday both at work and at home. John G4IJD __________________ Old radio engineers never die, they just go intermit...mit...mit...mit...

20th Dec 2014, 6:36 pm	#9
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: What type of coax connector? I had experience with tens of thousands of 75-Ohm BNC connectors - they were the type specified for use with 93-Ohm RG62A/U coax used to feed IBM "3270" displays http://www-01.ibm.com/support/knowle...61.htm?lang=en and their successors to 3214/3174 'cluster controllers' http://www.redbooks.ibm.com/Redbooks...l?OpenDocument IBM never bothered about the impedance mismatch from using 75-Ohm BNC connectors with 93-Ohm coax. I've always had a similarly permissive approach to mating 50- and 75-Ohm versions for generic RF applications below a couple of hundred MHz.

20th Dec 2014, 8:01 pm	#10
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: What type of coax connector? Isn't there a problem with different diameter centre pins? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

20th Dec 2014, 8:12 pm	#11
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: What type of coax connector? Yes but you generally get away with it!

21st Dec 2014, 1:24 am	#12
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,339	Re: What type of coax connector? I think it is the type N connectors where 50 and 75 ohm types should not be mated. My old Suhner catalogue says that 75 and 50 ohm BNC connectors can be mated without damage.

21st Dec 2014, 1:30 am	#13
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: What type of coax connector? Years ago we had a problem with a poor contact on a BNC female connector mounted on a transmitter duplexer and we put it down to someone using a 75 ohm BNC plug with a fatter pin forcing the contacts too far apart. A bit of careful realignment of the centre contact leafs cured the problem. I agree with Station X that you should only use the correct impedance connector plug/socket combination with BNCs. Alan.