
The BNC Connector and How It Got That Way - sohkamyung
https://hackaday.com/2018/10/19/the-bnc-connector-and-how-it-got-that-way/
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dylan604
I too felt the author’s snobbery towards lesser connectors. I felt the same
way towards equipment that did not have SDI as well. As cool as HDMI is, the
connector is just not a secure attachment. It is today’s equivalent of the
yellow/red/white video/audio jacks of older equipment. It is too easy for it
to be pulled out accidentally. The twist lock secured connection of BNC is
just reassuring.

~~~
M_Bakhtiari
SCART is another disgusting connector that European readers will be familiar
with. I like the idea of combining multiple video formats with sound as a
predecessor to HDMI, but the least they could have done was put a decent D-sub
or the Amphenol-style ribbon connector.

~~~
stormbrew
I recently got pretty heavily into SCART connectors because of retro video
game stuff (the most common rgb connector you can use with older consoles is
scart) and after a few months I've thrown it all away in exchange for special
component cables instead because scart is just terribad in terms of staying
connected.

Can't count the number of times I've had colour production go wonky just
because of a tiny bump of the scart cable.

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analog31
Hope it's OK to go off topic a bit and vent my gripe about connectors: You
bump the connector and destroy the printed circuit board that it lives on.

Well, at least I got an oscilloscope for free that way. The inputs were
flakey, and it was rejected by the calibration service. I opened it up, and
re-soldered the printed circuit mounted input connectors. Lovely scope.

~~~
wmf
Reliability isn't really off topic when talking about connector design.
Apparently there are possible tradeoffs between damaging the socket and the
cable; IIRC micro-USB is designed to sacrifice the cable to reduce damage to
the device.

~~~
tonyarkles
Funny enough, I had a $1200 software-defined radio that was destroyed when the
micro-USB3 connector ripped off the board, taking a bunch of traces with it.
When I ordered the replacement, it came with a full-sized connector on it
instead, with mechanical through-hole structural support. Some micro-USB
connectors have the through-hole support, but many are pure SMT devices that
will happily destroy your board with a sneeze.

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MickerNews
I always thought that these were called British Naval Connectors and were
developed for submarines. Not sure if I dreamt that or someone was having a
laugh with me.

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combatentropy
It is wrong but widespread,
[https://www.webopedia.com/TERM/B/BNC_connector.html](https://www.webopedia.com/TERM/B/BNC_connector.html)

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mcguire
"Bayonet Neil-Conselman"! Huh, who knew?

Speaking of connectors, once upon a time there was the IBM PC RT, whose mouse
and keyboard connected with these:

[https://fjkraan.home.xs4all.nl/comp/ibm6150/IBM_RT_keyboard_...](https://fjkraan.home.xs4all.nl/comp/ibm6150/IBM_RT_keyboard_mouse_connectors.jpg)

Those are the only connectors I've ever been able to plug into the back of a
box, from the front, without looking. They were wonderful (he says, tha
remembering at the time he was the guy who got to crawl around under peoples'
desks).

I was eventually told that, because the actual connectors were the same, they
had to add the keyed moldings to prevent the hardware from being destroyed by
being plugged into the wrong spot.

~~~
romwell
>"Bayonet Neil-Conselman"! Huh, who knew?

Indeed, it has been "bayonet network connector" in my mind. Must have been
some folk etymology that got stuck.

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MisterTea
They forgot to mention the alternative TNC, "Threaded Neil-Conselman". Same
connector dimensions but the barrel is threaded and the cable connector screws
on.

I mostly see them used on smaller RF gear like WiFi antennas, and whip
antennas on hand held radios. The threaded design provides a more secure
mechanical attachment. The classic blue Linksys routers and AP's use a reverse
TNC connector for the antennas.

~~~
29083011397778
They're actually still fairly common regarding aircraft radios. I see them
daily working with avionics, though BNC is more common.

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jamesfmilne
SDI is probably the main remaining prevalent signal being used with BNC
connectors, and 12G-SDI is going to be its last hurrah. 25G/100G Ethernet and
is rapidly displacing it.

The main thing SDI & coax has going for it is its robustness, especially for
3G-SDI signals, so I guess it will live on there. But BNC & SDI is on the way
out, certainly for broadcast. Its so much cheaper to use Mellanox, 25G/100G
Ethernet instead.

~~~
29083011397778
I'd assume it will be decades until BNC/TNC die off completely. I replaced one
today on a Bell 205A1 helicopter, for the ELT. Given the standards for
reliability (both in how well it must perform and how long it must last)
aircraft OEMs aim for, I expect to work with them for the remainder of my
career.

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computator
> _Like all coaxial connectors, it was designed to present as little change in
> the characteristic impedance of the feedline as possible by keeping the
> spacing between the center conductor connection and the outer shell as close
> to the feedline dimensions as possible._

The above supposedly explains why coax is better for high frequency, but the
sentence isn't parsing for me. Can anyone explain it a bit more?

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Junk_Collector
The characteristic impedance of a cable is distributed and depends on things
like the spatial relation of the connector to the shielding, other internal
conductors, and what the cable insulator is made of. Changes in these
parameters result in local impedance changes, when electrical signals
propagate down and reach changes in impedance, it cause reflections which show
up as noise and loss. The more abrupt and large the impedance change is, the
more extreme the reflections will be. Connectors are basically a hotspot for
changes in the physical dimensions of the cable as it connects to a
receptacle. Higher frequencies are more sensitive to changes in the physical
geometry because of their smaller wavelength. Most decent BNC connectors will
work up until a few GHz, most SMA up between 10 and 20 GHz. N connectors work
up to almost 30 GHz.

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ivan1783
RF guy here: N connectors are widely used in all RF equipment and are vastly
superior to BNC connectors. Good luck using a BNC connector above several GHz.
The second best connector used in RF is the SMA. The third most common is the
7/16 which is horrible in my opinion to work with but necessary for large
power transfer.

~~~
Junk_Collector
N connectors are robust, so they get used heavily in military applications and
that scale of production makes them relatively cheap and the mil-spec they are
produced to ensures that you don't get moding until 20 GHz. They are also huge
and a pain to put on. BNC is great for what it was designed for. Fast,
reliable, repeatable, connections in the 100's of MHz range.

HP/Agilent/Keysight uses a "Precision BNC" connector on their scopes that
easily outperforms N-type connectors in frequency response but is rather
expensive to produce.

SMA connectors are actually pretty crappy but are cheap, small, and
ubiquitous. Their size and forgiving PTFE dielectric makes them very forgiving
up to 10 GHz or so from a frequency response view point.

Really good high frequency connectors are going to be the precision
connectors, 3.5mm 2.92mm etc. down to 1.0mm which can go up and over 100 GHz
where you should really be using wave guides anyways. These types of
connectors are very expensive so you rarely see them in production electronics
unless absolutely required.

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stallmanite
Always wondered about these. Fascinating read, thanks for submitting.

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rb808
BTW is it time yet to improve on RJ-45? Esp as ethernet typically uses 4 wires
- its ridiculously large.

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Aloha
the RJ-45 is 8 wires, 4 pairs, and is designed to be easy to connect up by
field personnel, and be cheap.

~~~
AWildC182
This^ I actually quite like the design because it's so easy to create
connectors in the field with a couple simple tools. Don't have to strip the
conductors or solder anything, just cut the sheath off, align the wires and
shove it into the crimper.

Edit: and all this with connectors that are dirt cheap.

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js2
Popularly used by 10BASE2.

