BNC question
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
I want to use these isolated BNC connectors for a frequency
distribution amp. What do you think?
I'm still trying to find some old Ethernet cards for the transformers.
I know the cards will have BNC connectors, but the hub has eight
matched BNC connectors, so using them would be preferrable.
Joe Gray
W5JG
Hello Joe,
It probably is a 50 ohm BNC female connector.
Check out a male loose connector with a known 50 ohm center pin.
Does the male pin fit the female nicely ?
I have rarely seen a 75 ohm BNC center pin, but they are out there.
I have never seen a 93 ohm BNC center pin. (never looked for them.)
If you apply a true 75 ohm BNC male connector to a 50 ohm BNC female it
may not mate properly with a
low resistance joint. ie. poor mechanical fit.
If you apply a 50 ohm male BNC into a 75 ohm BNC female, you will
probably destroy the female center pin.
Cost wise, the 50 ohm BNC connectors are the least expensive, so that is
what manufacturers use.
For most applications the electrical length of the center pin is a very
small part of a wavelength,
so there is only a very small impact on the impedance, on the rare
occasion impedance is of concern.
Stan, W1LE
On 4/9/2011 6:53 PM, Joseph Gray wrote:
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
I want to use these isolated BNC connectors for a frequency
distribution amp. What do you think?
I'm still trying to find some old Ethernet cards for the transformers.
I know the cards will have BNC connectors, but the hub has eight
matched BNC connectors, so using them would be preferrable.
Joe Gray
W5JG
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi Stan this one has been covered before the pins are the same size the
difference is in the amount of dielectric round the socket in the
female....the 75 ohm one hase the socket poking free of the ptfe and on the
50 ohm it is flush with the end. The the centre connectors mate correctly
together.
Alan G3NYK
----- Original Message -----
From: "Stan, W1LE" stanw1le@verizon.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, April 10, 2011 12:32 AM
Subject: Re: [time-nuts] BNC question
Hello Joe,
It probably is a 50 ohm BNC female connector.
Check out a male loose connector with a known 50 ohm center pin.
Does the male pin fit the female nicely ?
I have rarely seen a 75 ohm BNC center pin, but they are out there.
I have never seen a 93 ohm BNC center pin. (never looked for them.)
If you apply a true 75 ohm BNC male connector to a 50 ohm BNC female it
may not mate properly with a
low resistance joint. ie. poor mechanical fit.
If you apply a 50 ohm male BNC into a 75 ohm BNC female, you will
probably destroy the female center pin.
Cost wise, the 50 ohm BNC connectors are the least expensive, so that is
what manufacturers use.
For most applications the electrical length of the center pin is a very
small part of a wavelength,
so there is only a very small impact on the impedance, on the rare
occasion impedance is of concern.
Stan, W1LE
On 4/9/2011 6:53 PM, Joseph Gray wrote:
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
I want to use these isolated BNC connectors for a frequency
distribution amp. What do you think?
I'm still trying to find some old Ethernet cards for the transformers.
I know the cards will have BNC connectors, but the hub has eight
matched BNC connectors, so using them would be preferrable.
Joe Gray
W5JG
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch
apparently didn't matter.
should work just fine as long as the connectors a good fit. Suspect it is.
On Sat, Apr 9, 2011 at 7:51 PM, Mike S mikes@flatsurface.com wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for 50
Ohm connectors. 75 Ohm ones don't have the insulator around the center
socket. Since ARCNET only ran at 2.5 MHz, the mismatch apparently didn't
matter.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 04/10/2011 01:51 AM, Mike S wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch apparently
didn't matter.
Risetime is the key aspect. If the impedance missmatch is sufficiently
small compared to the rise-time, it has no significant effect.
As I recall it ARCNET wasn't running at very high speeds and hence no
need for short rise-times.
Cheers,
Magnus
Magnus Danielson wrote:
On 04/10/2011 01:51 AM, Mike S wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch apparently
didn't matter.
Risetime is the key aspect. If the impedance missmatch is sufficiently
small compared to the rise-time, it has no significant effect.
As I recall it ARCNET wasn't running at very high speeds and hence no
need for short rise-times.
Cheers,
Magnus
There's also the minor issue of 0.7mm and 0.9mm diameter centre pin BNC
variants.
They do exist, I've seen hundreds of them.
Bruce
On 04/10/2011 01:44 PM, Bruce Griffiths wrote:
Magnus Danielson wrote:
On 04/10/2011 01:51 AM, Mike S wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch apparently
didn't matter.
Risetime is the key aspect. If the impedance missmatch is sufficiently
small compared to the rise-time, it has no significant effect.
As I recall it ARCNET wasn't running at very high speeds and hence no
need for short rise-times.
Cheers,
Magnus
There's also the minor issue of 0.7mm and 0.9mm diameter centre pin BNC
variants.
They do exist, I've seen hundreds of them.
These days there exists a standard variant of the BNC for 75 Ohm which
is mechanical compatible with 50 Ohm. So that is what I recommend using.
75 Ohm BNC dominate with margin over 50 Ohm BNC at work. Our rise-times
makes connector-choices more relevant.
Cheers,
Magnus
From what I recall from our candle lit lab, the 75 ohm
BNCs had a slightly larger pin and would open up the
50 ohm females just a skoosh so when you put a
50 ohm, into a 50 ohm that had been tweaked by a
75 ohm, they were noisy or intermittent.
Greg
On 4/10/2011 5:30 AM, Magnus Danielson wrote:
On 04/10/2011 01:51 AM, Mike S wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch apparently
didn't matter.
Risetime is the key aspect. If the impedance missmatch is sufficiently
small compared to the rise-time, it has no significant effect.
As I recall it ARCNET wasn't running at very high speeds and hence no
need for short rise-times.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
I had remembered that it was a 75 ohm that would damage a
50 ohm socket. This article states that a 50 ohm would
damage a 75 ohm socket.
Greg
Indeed, the 75-ohm will have the smaller inner, and hence may be damaged
by the larger pin on the 50-ohm connector.
David
GM8ARV
SatSignal software - quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Types
BNC connectors exist in 50 and 75ohm
http://en.wikipedia.org/wiki/Ohmversions, matched for use with
cables of the samecharacteristic impedance
http://en.wikipedia.org/wiki/Characteristic_impedance. The 75 ohm
types can sometimes be recognized by the reduced or absentdielectric
http://en.wikipedia.org/wiki/Dielectricin the mating ends. The 50
and 75 ohm connectors are typically specified for use at frequencies
up to 4 and 2 GHz respectively.
75 ohm BNC Connectors are primarily used for video andDS3
http://en.wikipedia.org/wiki/Digital_Signal_3Telco central office
applications^[/clarification needed
http://en.wikipedia.org/wiki/Wikipedia:Please_clarify/] , whereas 50
ohm are used for data and RF. TheBBC
http://en.wikipedia.org/wiki/British_Broadcasting_Corporationhad a
convention that BNC connectors used for video were always 50 ohm,
maybe because an accidentally connected 50 ohm plug would damage a 75
ohm socket.^[/dubious
http://en.wikipedia.org/wiki/Wikipedia:Disputed_statement--discuss
http://en.wikipedia.org/wiki/Talk:BNC_connector#Video/] Many VHF
receivers used 75 ohmantenna
http://en.wikipedia.org/wiki/Antenna_%28radio%29inputs, so they
often used 75 ohm BNC connectors.
I had remembered that it was a 75 ohm that would damage a
50 ohm socket. This article states that a 50 ohm would
damage a 75 ohm socket.
Greg
On 4/10/2011 9:25 AM, Greg Broburg wrote:
From what I recall from our candle lit lab, the 75 ohm
BNCs had a slightly larger pin and would open up the
50 ohm females just a skoosh so when you put a
50 ohm, into a 50 ohm that had been tweaked by a
75 ohm, they were noisy or intermittent.
Greg
On 4/10/2011 5:30 AM, Magnus Danielson wrote:
On 04/10/2011 01:51 AM, Mike S wrote:
At 06:53 PM 4/9/2011, Joseph Gray wrote...
I have an old Arcnet hub that I want to salvage the isolated BNC
connectors from. Arcnet used 93 Ohm coax. I know that there are 50 Ohm
and 75 Ohm versions of BNC connectors, but the ones from the hub look
like a 50 Ohm BNC to me.
The ARCNET spec states: "The MIC for use with coaxial cable is a
conventional BNC per MIL-STD-348A." If you look at that spec, it's for
50 Ohm connectors. 75 Ohm ones don't have the insulator around the
center socket. Since ARCNET only ran at 2.5 MHz, the mismatch
apparently
didn't matter.
Risetime is the key aspect. If the impedance missmatch is
sufficiently small compared to the rise-time, it has no significant
effect.
As I recall it ARCNET wasn't running at very high speeds and hence no
need for short rise-times.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Greg Broburg wrote:
receivers used 75 ohmantenna
http://en.wikipedia.org/wiki/Antenna_%28radio%29inputs, so they
often used 75 ohm BNC connectors.
I had remembered that it was a 75 ohm that would damage a
50 ohm socket. This article states that a 50 ohm would
damage a 75 ohm socket.
Greg
Sadly, you remembered incorrectly. Both 75 ohm, and 50 ohm
BNC parts use the same center pin assemblies. The only
difference is the 75 ohm part has the teflon shroud removed
from around the female pin. They mate in all combinations
without any risk of damage.
The N style connector is a different story, however. It is
a higher performance connector, and as a result they needed
to make the center conductor of a 75 ohm connector smaller
in diameter all the way through, so the 75 ohm center male
pin is slender, as is the 75 ohm center female pin. If you
jam a thicker 50 ohm center pin into the slender 75 ohm
female pin, it will bend the socket leafs out and probably
break it.
-Chuck Harris
Chuck Harris wrote:
Greg Broburg wrote:
receivers used 75 ohmantenna
http://en.wikipedia.org/wiki/Antenna_%28radio%29inputs, so they
often used 75 ohm BNC connectors.
I had remembered that it was a 75 ohm that would damage a
50 ohm socket. This article states that a 50 ohm would
damage a 75 ohm socket.
Greg
Sadly, you remembered incorrectly. Both 75 ohm, and 50 ohm
BNC parts use the same center pin assemblies. The only
difference is the 75 ohm part has the teflon shroud removed
from around the female pin. They mate in all combinations
without any risk of damage.
Not necessarily true, BNCs intended for use with RG59 cable with either
a 0.7mm diameter pin or a 0.9mm diameter pin are readily available.
Whilst one of these may now be non standard they are nevertheless they
are still available from Chinese manufacturers at least.
The N style connector is a different story, however. It is
a higher performance connector, and as a result they needed
to make the center conductor of a 75 ohm connector smaller
in diameter all the way through, so the 75 ohm center male
pin is slender, as is the 75 ohm center female pin. If you
jam a thicker 50 ohm center pin into the slender 75 ohm
female pin, it will bend the socket leafs out and probably
break it.
-Chuck Harris
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Thanks for all the input. I looked closely at the connectors and they
seem to match some 50 Ohm connectors that I have. I have removed them
from the board and now have eight isolated BNC connectors for my
project.
Joe Gray
W5JG