Bnc impedance

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So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf
 
On Sunday, April 2, 2017 at 5:11:02 PM UTC-4, jfish...@comcast.net wrote:
> So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

Some missile/radar systems use 90ohm internally. Really sucks trying to use regular 50 ohm equipment to troubleshoot.
 
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics
Click to expand...

I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.

--
www.wescottdesign.com


----Android NewsGroup Reader----
http://usenet.sinaapp.com/
 
Tim Wescott wrote:


I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.
Click to expand...

** BNCs are rated to 4GHz and beyond.

https://en.wikipedia.org/wiki/BNC_connector


...... Phil
 
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
<jfisher864@comcast.net> wrote:

>So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
Tim Wescott wrote:
Phil Allison wrote:

I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.



** BNCs are rated to 4GHz and beyond.

OK, so I was off by 10dB -- I got the significant figure correct.
Click to expand...

** Lemme see,

1. You did not bother to look up the info.

2. You are unaware of any of the communications gear that uses BNC for antenna inputs up to the several GHz.

4. You were unaware of RF test gear that uses BNCs up to 4GHz.


Nothing to pat yourself on the back for here.


..... Phil
 
On Sun, 02 Apr 2017 17:43:29 -0700, Phil Allison wrote:

Tim Wescott wrote:



I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.



** BNCs are rated to 4GHz and beyond.
Click to expand...

OK, so I was off by 10dB -- I got the significant figure correct.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com
 
John Larkin wrote:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?
Click to expand...

Old car radios, early IBM computer terminals.

RG62 is 93 Ohms.

--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)
 
On Sunday, April 2, 2017 at 5:11:02 PM UTC-4, jfish...@comcast.net wrote:
> So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

I know little about HF RF. But I would think a mis-matched connector
is not going to cause all that much of a problem.
I'd certainly add termination resistors at the receive end. And maybe
a series resistor from a 50 ohm signal generator at the source end.

Or throw-away signal at the source end and make a resistor Tee that
look like 50 ohms in and 92 ohms out... (Hey is that possible?)

George H.
 
On Sun, 2 Apr 2017 17:39:21 -0700 (MST), Tim Wescott
<Tim@seemywebsite.com> wrote:

John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics



I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.
Click to expand...

With decent quality cables and connectors, BNCs are good to 3 GHz or
so. TNC is rare these days; most people go to SMA at higher
frequencies. Some RF test gear still uses type N, and if we have that
we scrunch on an SMA or BNC adapter.

We use a lot of SMBs on our boxes, because they are easy to
mate/unmate (SMAs are a pain) and they can be spaced close. SMBs are
good to at least 10 GHz.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
I'm using nim electronics,the pulses from my photomultiplier are about 10 NSA.
 
That's nanosecond not NSA, I'm using a Ortec pulser .
 
On 03/04/17 02:39, Tim Wescott wrote:
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics



I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.
Click to expand...

Much depends on how good you need it to be. I did some TDR
measurements on various connectors, or between-series adapters
really, but that gave a good view of the relative merits of
SMA, N, BNC, SMC and LEMO-00 50 Ohm connectors.

See <http://cern.ch/jeroen/connectorTDR>.

Sorry, no TNC in there.

Jeroen Belleman
 
On Mon, 03 Apr 2017 23:05:09 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 03/04/17 02:39, Tim Wescott wrote:
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics



I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.


Much depends on how good you need it to be. I did some TDR
measurements on various connectors, or between-series adapters
really, but that gave a good view of the relative merits of
SMA, N, BNC, SMC and LEMO-00 50 Ohm connectors.

See <http://cern.ch/jeroen/connectorTDR>.

Sorry, no TNC in there.

Jeroen Belleman
Click to expand...

Good grief, that LEMO terminator is awful.

A lot of cheap terminators have an ordinary axial thick-film (spiral
element!) resistor inside.

https://dl.dropboxusercontent.com/u/53724080/TDR/51R_setup.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/51R_TDR.JPG

Surface-mount resistors are usually pretty good.

https://dl.dropboxusercontent.com/u/53724080/TDR/47R_0805_fixture.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/47R_0805_TDR1.JPG



Here is a mess of SMBs, both TDR and TDT.

https://dl.dropboxusercontent.com/u/53724080/TDR/SMB_1.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/SMB_2.JPG

The output is pretty clean, 37 ps risetime, which is almost 10 GHz.

Some BNCs:

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDR_TDT.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDR_ZOOM.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDT_RISE.JPG


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Mon, 3 Apr 2017 13:15:18 -0700 (PDT), "jfisher864@comcast.net"
<jfisher864@comcast.net> wrote:

>I'm using nim electronics,the pulses from my photomultiplier are about 10 NSA.

50 or 75 ohm BNC connectors will be fine at 10 ns. But the comment
"use 92ohm terminators on all my T's" is sort of scary. Can you post a
sketch of the proposed setup?

CAMAC is dead, but I guess that NIM is still around.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On 04/04/17 05:19, John Larkin wrote:
On Mon, 3 Apr 2017 13:15:18 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

I'm using nim electronics,the pulses from my photomultiplier are about 10 NSA.

50 or 75 ohm BNC connectors will be fine at 10 ns. But the comment
"use 92ohm terminators on all my T's" is sort of scary. Can you post a
sketch of the proposed setup?

CAMAC is dead, but I guess that NIM is still around.
Click to expand...

I started my career debugging CAMAC and NIM modules. Somewhat
later also FastBus and VME. CAMAC and FastBus are all but dead,
but we still have a lot of NIM bins. Simple is better, I suppose.

Jeroen Belleman
 
On Tue, 04 Apr 2017 21:44:18 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 04/04/17 05:19, John Larkin wrote:
On Mon, 3 Apr 2017 13:15:18 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

I'm using nim electronics,the pulses from my photomultiplier are about 10 NSA.

50 or 75 ohm BNC connectors will be fine at 10 ns. But the comment
"use 92ohm terminators on all my T's" is sort of scary. Can you post a
sketch of the proposed setup?

CAMAC is dead, but I guess that NIM is still around.




I started my career debugging CAMAC and NIM modules. Somewhat
later also FastBus and VME. CAMAC and FastBus are all but dead,
but we still have a lot of NIM bins. Simple is better, I suppose.

Jeroen Belleman
Click to expand...

I did a lot of CAMAC too, modules and even crates and crate
controllers. It was sort of a goofy bus, designed by physicists. The
good parts were the geographic board select and interrupt lines.

VME is still alive. It has survived the many other busses that were
supposed to kill it off.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Sunday, April 2, 2017 at 2:50:00 PM UTC-7, John Larkin wrote:

> What kind of equipment is 92 ohms?

Old, usually. A 7400 gate can sink 16 mA. To drive a 93 ohm
load with 3.5V, you need 38 mA.

So there were 'bus driver' gates made, SN7438, with open
collector output and 48 mA drive.

A few decades back it made good sense to run 93 ohm cable,
because that meant you could use mass-produced drivers and
regular ol' TTL for receivers.
 
On Monday, April 3, 2017 at 11:19:09 PM UTC-4, John Larkin wrote:
On Mon, 3 Apr 2017 13:15:18 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

I'm using nim electronics,the pulses from my photomultiplier are about 10 NSA.

50 or 75 ohm BNC connectors will be fine at 10 ns. But the comment
"use 92ohm terminators on all my T's" is sort of scary. Can you post a
sketch of the proposed setup?
Click to expand...
He's terminating his cable with a bnc Tee and resistor.
I've done that with ~20' of cable from a PMT to some crate.
(50 ohm cable)
We'd put Tee's on both ends, 1/2 the signal, but less bounce on
big pulses.

George H.
CAMAC is dead, but I guess that NIM is still around.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
Click to expand...
 
On Mon, 03 Apr 2017 15:37:11 -0700, John Larkin
<jjlarkinxyxy@highlandtechnology.com> wrote:

On Mon, 03 Apr 2017 23:05:09 +0200, Jeroen Belleman
jeroen@nospam.please> wrote:

On 03/04/17 02:39, Tim Wescott wrote:
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:
On Sun, 2 Apr 2017 14:10:56 -0700 (PDT), "jfisher864@comcast.net"
jfisher864@comcast.net> wrote:

So I am using rg 62 coax which is 92 ohm. My BNC connectors are 75ohm.all my equipment inputs and outputs are 92ohm. Do I need to use 92ohm terminators on all my T's and where,at the source or load? Thanks jf

If your frequency is below, say, 1 GHz, the connector impedances won't
matter, as long as they mate mechanically.

One usually tee-terminates a coax at the load end. If your frequency
is low compared to the cable length, you probably don't need to
terminate at all.

What kind of equipment is 92 ohms?




--

John Larkin Highland Technology, Inc

lunatic fringe electronics



I thought that BNC was only good to 400MHz or so, and that you
wanted TNC above that.


Much depends on how good you need it to be. I did some TDR
measurements on various connectors, or between-series adapters
really, but that gave a good view of the relative merits of
SMA, N, BNC, SMC and LEMO-00 50 Ohm connectors.

See <http://cern.ch/jeroen/connectorTDR>.

Sorry, no TNC in there.

Jeroen Belleman

Good grief, that LEMO terminator is awful.

A lot of cheap terminators have an ordinary axial thick-film (spiral
element!) resistor inside.

https://dl.dropboxusercontent.com/u/53724080/TDR/51R_setup.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/51R_TDR.JPG

Surface-mount resistors are usually pretty good.

https://dl.dropboxusercontent.com/u/53724080/TDR/47R_0805_fixture.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/47R_0805_TDR1.JPG



Here is a mess of SMBs, both TDR and TDT.

https://dl.dropboxusercontent.com/u/53724080/TDR/SMB_1.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/SMB_2.JPG

The output is pretty clean, 37 ps risetime, which is almost 10 GHz.

Some BNCs:

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDR_TDT.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDR_ZOOM.JPG

https://dl.dropboxusercontent.com/u/53724080/TDR/BNC_TDT_RISE.JPG
Click to expand...

Good work, boy. Hope the pay you well.

w.
 
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