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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
Good work, boy. Hope the pay you well.
w.