18 Jan
2011
18 Jan
'11
11 p.m.
hi everybody!
forgive the ot post, but i hope there are some brains to pick here.
i'm planning a studio, and to make it future-proof, there is coax in
every room. currently it's going to be used for rgbhv and composite
video, but i want it to be future-proof for MADI and HD-SDI.
the cabling itself is of sufficient quality, but i'm doubtful about the
connectors. the whole installation has a star topology, so the worst case is
* source
* 5m or so of suitable cable
* bnc wall socket
* 20m installation cable (-63dB/100m @ 3ghz)
* a ghielmetti patchbay (which includes two canare contacts to the patch
cord and two bnc on the rear, unfortunately)
* another 20m installation cable
* bnc wall socket
* another 5m cable
* sink
question 1: any hopes for reliable hd-sdi?
question 2: how can it be that a kick-ass company like ghielmetti does
not offer video patchbays that allow direct connection of coax
installation cables, but require rear bnc connections instead?
question 2b: is there an alternative for direct rear coax connection,
thereby cutting out two potentially disruptive contact surfaces?
question 3: i'm thinking of getting neutrik isolated bnc connectors (the
d-type ones that are semi-recessed and thus well protected from clumsy
passers-by). but their soldering lugs break the coaxial structure -
cause for concern?
question 4: do i really want to solder hf stuff (even though the
voltages are not too high), or will it unsolder itself eventually? any
recommendations as to procedures and tin?
thanks in advance,
jörn
18 Jan
18 Jan
11:29 p.m.
Hi Joern,
If it is an option: use Leerrohre (DE for "empty tubes" ?) to make it
future-proof, rather than to rely on cable-standards. In a few years you
may want to replace coax with optical or whatever.
The only question I can answer is #4: The problem is reflections caused
by skin-effect if you do solder them. Back in the days that I spent in
the physics dept. we used solder-less crimp connectors for everything
high-freq.
On 01/18/2011 10:59 PM, Jörn Nettingsmeier wrote:
hi everybody!
forgive the ot post, but i hope there are some brains to pick here.
i'm planning a studio, and to make it future-proof, there is coax in
every room. currently it's going to be used for rgbhv and composite
video, but i want it to be future-proof for MADI and HD-SDI.
the cabling itself is of sufficient quality, but i'm doubtful about the
connectors. the whole installation has a star topology, so the worst
case is
* source
* 5m or so of suitable cable
* bnc wall socket
* 20m installation cable (-63dB/100m @ 3ghz)
* a ghielmetti patchbay (which includes two canare contacts to the patch
cord and two bnc on the rear, unfortunately)
* another 20m installation cable
* bnc wall socket
* another 5m cable
* sink
question 1: any hopes for reliable hd-sdi?
question 2: how can it be that a kick-ass company like ghielmetti does
not offer video patchbays that allow direct connection of coax
installation cables, but require rear bnc connections instead?
question 2b: is there an alternative for direct rear coax connection,
thereby cutting out two potentially disruptive contact surfaces?
question 3: i'm thinking of getting neutrik isolated bnc connectors (the
d-type ones that are semi-recessed and thus well protected from clumsy
passers-by). but their soldering lugs break the coaxial structure -
cause for concern?
question 4: do i really want to solder hf stuff (even though the
voltages are not too high), or will it unsolder itself eventually? any
recommendations as to procedures and tin?
thanks in advance,
jörn
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19 Jan
19 Jan
3:39 a.m.
On Tuesday, January 18, 2011 09:16:00 pm Robin Gareus did opine:
Hi Joern,
If it is an option: use Leerrohre (DE for "empty tubes" ?) to make it
future-proof, rather than to rely on cable-standards. In a few years you
may want to replace coax with optical or whatever.
I think that would translate to wave-guides in English, but check your
sizes, at 3Ghz, they are hundreds of times greater cross sectional area
than a coax would be. Also, a lot less loss if properly terminated. 250
feet of it has less loss than 3 feet of this mini-coax in common use now,
but you would have at least $20k in that 250 feet too.
In short, optical seems the best way to go. I helped setup a fiber link
several years ago that was 39 kilometers long, and the end to end optical
loss was 0.5 db. You can't do that with wave-guide or a G-Line, and coax
would have likely been 60-80db of loss and much less bandwidth, we stuffed
4 television channels though that fiber.
The only question I can answer is #4: The problem is
reflections caused
by skin-effect if you do solder them. Back in the days that I spent in
the physics dept. we used solder-less crimp connectors for everything
high-freq.
I can't testify about 3Gb+ solder joints, but I do know that properly done,
they are invisible at .6 Ghz. You may have to putz with it a bit, but it
CAN be done.
And, I have yet to see a physics prof that actually knew which end of the
iron got hot, let alone could actually make a good joint. Too many have
the attitude that their hands do not fit the tools and make no effort to
teach themselves how to do it.
I will allow the comment that when fabricating wave-guide parts and filters
for 7Ghz work, which I have done a few of decades ago, those were usually
silver soldered because the regular tin/lead solders surfaces oxidized with
time much worse, screwing with the skin effect losses. Silver oxide may
look fugly, but is still a pretty fair conductor when frequencies are in
the realm where skin effect reigns supreme. Just as true inside the wave-
guide as it is on the skin of a coax conductor.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
After twelve years of therapy my psychiatrist said something that
brought tears to my eyes. He said, "No hablo ingles."
-- Ronnie Shakes
4:35 a.m.
On 01/19/2011 03:39 AM, gene heskett wrote:
On Tuesday, January 18, 2011 09:16:00 pm Robin Gareus
did opine:
nope. I mean tubes like pipes in the wall or floor that allow one to
easily replace cables that run inside those tubes. It'd still be a major
re-wiring task but at least one can change the wires easily compared to
in-wall mounted cables.
Some trivial mechanical suggestion for a future-proof studio (not an
electrical one) at least if future > 10 years and esp. if you don't want
to rip the whole studio apart for major renovation.
but wave-guides are a good drift.
Hi Joern,
If it is an option: use Leerrohre (DE for "empty tubes" ?) to make it
future-proof, rather than to rely on cable-standards. In a few years you
may want to replace coax with optical or whatever.
I think that would translate to wave-guides in English but check your
sizes, at 3Ghz, they are hundreds of times greater cross sectional area
than a coax would be. Also, a lot less loss if properly terminated. 250
feet of it has less loss than 3 feet of this mini-coax in common use now,
but you would have at least $20k in that 250 feet too.
In short, optical seems the best way to go. I helped setup a fiber link
several years ago that was 39 kilometers long, and the end to end optical
loss was 0.5 db. You can't do that with wave-guide or a G-Line, and coax
would have likely been 60-80db of loss and much less bandwidth, we stuffed
4 television channels though that fiber.
sure, one question is if it can be done by Joern and another is if
shelling out more euros for a proper crimp-on connectors is worth not to
worry about possible bad solder joints.
The only question I can answer is #4: The problem
is reflections caused
by skin-effect if you do solder them. Back in the days that I spent in
the physics dept. we used solder-less crimp connectors for everything
high-freq.
I can't testify about 3Gb+ solder joints, but I do know that properly done,
they are invisible at .6 Ghz. You may have to putz with it a bit, but it
CAN be done. And, I have yet to see a physics prof that actually
knew which end of the
iron got hot, let alone could actually make a good joint. Too many have
the attitude that their hands do not fit the tools and make no effort to
teach themselves how to do it.
LOL.
This was/is experimental physics in cooperation with
hardware-informatics. Eventually we designed custom ASICs and did the
PCBs and soldering of the prototypes ourself, pretty much everything is
non-standard since it must be able to work in a >5 Tesla magnetic field.
It is currently running inside the ALICE detector @LHC.
I will allow the comment that when fabricating
wave-guide parts and filters
for 7Ghz work, which I have done a few of decades ago, those were usually
silver soldered because the regular tin/lead solders surfaces oxidized with
time much worse, screwing with the skin effect losses. Silver oxide may
look fugly, but is still a pretty fair conductor when frequencies are in
the realm where skin effect reigns supreme. Just as true inside the wave-
guide as it is on the skin of a coax conductor.
interesting. I do remember a drawer with at least 15 different kind of
solder. Now I know what that silver stuff in there was in there for :)
Cheers!
robin
6:35 a.m.
On Wednesday, January 19, 2011 12:12:05 am Robin Gareus did opine:
Thought someone might like that.
Silver solder, or just silver bearing solder? The latter seems to top out
at about 3% siver in an otherwise eutectic allow, but is a noticeably
stronger solder mechanically that doesn't oxidize near as fast. I don't
use anything else myself but it does raise the iron temps needed by
50-100F, which leads to needing to clean the tips more often.
Real silver solder needs a propane or better torch or a tig for heat and
you use a borax based flux that melts and forms an airtight puddle of
liquid glass over the joint so the oxygen is sealed away from the hot
metal, facilitating a nice clean joint when you feed the silver wire in to
make a 'sweat' joint, like the plumbers do for copper piping. But the
borax should be chipped away and removed once it has cooled as its a bit
lossy at those frequencies. Properly done, you get the 'sweat' started,
and pull it along by moving the heat (it crawls to the heat) until you have
the joint level full of silver but no extra beads sticking out. Don't
apply any more silver than what it takes to just seal the joint. Dry fit
accuracies of less than a 5 thou gap work very well, wider gaps are
correspondingly harder to control. You really need a milling machine to do
wave-guide parts correctly.
Thanks robin
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
You have a deep interest in all that is artistic.
On 01/19/2011 03:39 AM, gene heskett wrote:
Ahh, so, here that is called "conduit" and can be metallic or more likely
in recent years, plastic, glued up just like water pipe and smoother to
pull wires through than the metallic stuff. Both need plenty of "snot" on
the wires for a temp lubricant if going very far, and about 3 bends is
still the limit for one pull run.
On Tuesday, January 18, 2011 09:16:00 pm Robin
Gareus did opine:
nope. I mean tubes like pipes in the wall or floor that allow one to
easily replace cables that run inside those tubes. It'd still be a major
re-wiring task but at least one can change the wires easily compared to
in-wall mounted cables.
Hi Joern,
If it is an option: use Leerrohre (DE for "empty tubes" ?) to make it
future-proof, rather than to rely on cable-standards. In a few years
you may want to replace coax with optical or whatever.
I think that would translate to wave-guides in English Some trivial mechanical suggestion for a future-proof
studio (not an
electrical one) at least if future > 10 years and esp. if you don't want
to rip the whole studio apart for major renovation.
but wave-guides are a good drift.
Keyword there is proper, there is a lot of trash for sale at Radio Shack &
friends.
but check your
sizes, at 3Ghz, they are hundreds of times greater cross sectional
area than a coax would be. Also, a lot less loss if properly
terminated. 250 feet of it has less loss than 3 feet of this
mini-coax in common use now, but you would have at least $20k in that
250 feet too.
In short, optical seems the best way to go. I helped setup a fiber
link several years ago that was 39 kilometers long, and the end to
end optical loss was 0.5 db. You can't do that with wave-guide or a
G-Line, and coax would have likely been 60-80db of loss and much less
bandwidth, we stuffed 4 television channels though that fiber.
sure, one question is if it can be done by Joern and another is if
shelling out more euros for a proper crimp-on connectors is worth not to
worry about possible bad solder joints. The only question I can answer is #4: The problem
is reflections
caused by skin-effect if you do solder them. Back in the days that I
spent in the physics dept. we used solder-less crimp connectors for
everything high-freq.
I can't testify about 3Gb+ solder joints, but I do know that properly
done, they are invisible at .6 Ghz. You may have to putz with it a
bit, but it CAN be done. And, I have
yet to see a physics prof that actually knew which end of
the iron got hot, let alone could actually make a good joint. Too
many have the attitude that their hands do not fit the tools and make
no effort to teach themselves how to do it.
LOL. This was/is experimental physics in cooperation with
hardware-informatics. Eventually we designed custom ASICs and did the
PCBs and soldering of the prototypes ourself, pretty much everything is
non-standard since it must be able to work in a >5 Tesla magnetic field.
It is currently running inside the ALICE detector @LHC.
Yikes. If that ever collapses, it will emp into smoke, and and all
electrical stuff for many meters around it. That, it can be said is NOT a
friendly environment. Even your $15 Casio wrist watch is in danger if you
move too fast in that.
I will allow
the comment that when fabricating wave-guide parts and
filters for 7Ghz work, which I have done a few of decades ago, those
were usually silver soldered because the regular tin/lead solders
surfaces oxidized with time much worse, screwing with the skin effect
losses. Silver oxide may look fugly, but is still a pretty fair
conductor when frequencies are in the realm where skin effect reigns
supreme. Just as true inside the wave- guide as it is on the skin of
a coax conductor.
interesting. I do remember a drawer with at least 15 different kind of
solder. Now I know what that silver stuff in there was in there for :)
12:56 p.m.
On 01/19/2011 06:35 AM, gene heskett wrote:
nah It will pull itself into a black hole of course :)
Silver solder, or just silver bearing solder?
likely both. It is a very well equipped lab. There was a small
hand-torch in there as well. Though I think it was mostly used as a
spare lighter :)
On Wednesday, January 19, 2011 12:12:05 am Robin
Gareus did opine:
I guess Joern's Studio is only 3 or 4 rooms. It's mostly because he
mentioned wall sockets that I suggested this.
It can also be the wall (or ceiling-mounted) type. I think they're
called raceways or just cable-tray.
[..]
On 01/19/2011 03:39 AM, gene heskett wrote:
Ahh, so, here that is called "conduit" and can be metallic or more likely
in recent years, plastic, glued up just like water pipe and smoother to
pull wires through than the metallic stuff. Both need plenty of "snot" on
the wires for a temp lubricant if going very far, and about 3 bends is
still the limit for one pull run. On Tuesday, January 18, 2011 09:16:00 pm Robin
Gareus did opine:
nope. I mean tubes like pipes in the wall or floor that allow one to
easily replace cables that run inside those tubes. It'd still be a major
re-wiring task but at least one can change the wires easily compared to
in-wall mounted cables.
Hi Joern,
If it is an option: use Leerrohre (DE for "empty tubes" ?) to make it
future-proof, rather than to rely on cable-standards. In a few years
you may want to replace coax with optical or whatever.
I think that would translate to wave-guides in English It is
currently running inside the ALICE detector @LHC.
Yikes. If that ever collapses, it will emp into smoke, and and all
electrical stuff for many meters around it. That, it can be said is NOT a
friendly environment. Even your $15 Casio wrist watch is in danger if you
move too fast in that.
The magnetic field you mean? The tricky part is get close enough. You'll
need a few weeks to undo all the screws on the "enclosure" and not get
kicked out in the meantime. Once you get in there you don't need to
move, the electrons inside the watch are already moving fast enough. The
only workaround is to have only short interconnects and lots of bulk in
between them. Luckily this is an OT post:
http://blogs.discovermagazine.com/badastronomy/2010/09/21/dont-cross-the-lh…
I will allow the comment that when fabricating
wave-guide parts and
filters for 7Ghz work, which I have done a few of decades ago, those
were usually silver soldered because the regular tin/lead solders
surfaces oxidized with time much worse, screwing with the skin effect
losses. Silver oxide may look fugly, but is still a pretty fair
conductor when frequencies are in the realm where skin effect reigns
supreme. Just as true inside the wave- guide as it is on the skin of
a coax conductor.
interesting. I do remember a drawer with at least 15 different kind of
solder. Now I know what that silver stuff in there was in there for :) The latter seems to top out
at about 3% siver in an otherwise eutectic allow, but is a noticeably
stronger solder mechanically that doesn't oxidize near as fast. I don't
use anything else myself but it does raise the iron temps needed by
50-100F, which leads to needing to clean the tips more often.
Real silver solder needs a propane or better torch or a tig for heat and
you use a borax based flux that melts and forms an airtight puddle of
liquid glass over the joint so the oxygen is sealed away from the hot
metal, facilitating a nice clean joint when you feed the silver wire in to
make a 'sweat' joint, like the plumbers do for copper piping. But the
borax should be chipped away and removed once it has cooled as its a bit
lossy at those frequencies. Properly done, you get the 'sweat' started,
and pull it along by moving the heat (it crawls to the heat) until you have
the joint level full of silver but no extra beads sticking out. Don't
apply any more silver than what it takes to just seal the joint. Dry fit
accuracies of less than a 5 thou gap work very well, wider gaps are
correspondingly harder to control. You really need a milling machine to do
wave-guide parts correctly.
Thanks robin
Thank you for the lengthy explanation.
ciao,
robin
1:54 p.m.
On Wednesday, January 19, 2011 07:25:59 am Robin Gareus did opine:
nah It will pull itself into a black hole of course :)
They tried that once, took about a year to rebuild things IIRC. :(
Interesting what drifting conversations do when brains get together.
[...]
And of course its out of gas if you need to fire it up and get enough heat
out of it to do a silver joint. There is a Murphy's Law corollary about
that I've seen someplace. ;-)
[...]
On 01/19/2011 06:35 AM, gene heskett wrote:
[...]
I guess Joern's Studio is only 3 or 4 rooms.
It's mostly because he
mentioned wall sockets that I suggested this.
It can also be the wall (or ceiling-mounted) type. I think they're
called raceways or just cable-tray.
Yup.
It is currently running inside the ALICE detector
@LHC.
Yikes. If that ever collapses, it will emp into smoke, and and all
electrical stuff for many meters around it. That, it can
be said is NOT a
friendly environment. Even your $15 Casio wrist watch is in danger if
you move too fast in that.
The magnetic field you mean? The tricky part is get close enough. You'll
need a few weeks to undo all the screws on the "enclosure" and not get
kicked out in the meantime. Once you get in there you don't need to
move, the electrons inside the watch are already moving fast enough. The
only workaround is to have only short interconnects and lots of bulk in
between them. Luckily this is an OT post:
http://blogs.discovermagazine.com/badastronomy/2010/09/21/dont-cross-the
-lhc-stream/ Silver solder,
or just silver bearing solder?
likely both. It is a very well equipped lab. There was a small
hand-torch in there as well. Though I think it was mostly used as a
spare lighter :)
Thank you for the lengthy explanation.
NP. When I get started, like most old farts with a loooong history in
broadcasting, I don't know when its time to shut up. ;-)
ciao,
robin
Thanks Robin
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
No two persons ever read the same book.
-- Edmund Wilson
12:18 a.m.
On Tue, Jan 18, 2011 at 10:59:59PM +0100, Jörn Nettingsmeier wrote:
* source
* 5m or so of suitable cable
* bnc wall socket
* 20m installation cable (-63dB/100m @ 3ghz)
* a ghielmetti patchbay (which includes two canare contacts to the
patch cord and two bnc on the rear, unfortunately)
* another 20m installation cable
* bnc wall socket
* another 5m cable
* sink
question 1: any hopes for reliable hd-sdi?
Can't really answer this. But BNC seems to be the standard
connector for this, so it's probably OK.
question 2: how can it be that a kick-ass company like
ghielmetti
does not offer video patchbays that allow direct connection of coax
installation cables, but require rear bnc connections instead?
This is probably just a question of being practical. Wiring up
a patch bay to things outside the rack (or the equipment it is
part of) without connectors leaves you with something that is more
or less cast in stone. It can also be quite difficult to install.
I recently wired up a 96 point audio patchbay without rear
connectors (i.e. soldered), with almost all of the connections
going outside. Luckily these cables had the other end free and
didn't go into some wall. But I'll avoid to do that again...
I doing another one these days (the Sala dei Concerti - you know
the system needs some rewiring :-) but this time the patchbay has
rear connectors - it would be near impossible get it wired up
otherwise.
question 2b: is there an alternative for direct rear
coax
connection, thereby cutting out two potentially disruptive contact
surfaces?
Haven't seen it. When I was working at Alcatel, all HF racks we
constructed had back panels with double through-panel BNCs for
external connections. No external cable would ever be attached
directly to any of the equipment inside the rack. And more often
than not, the same through-panel BNCs were used on the actual
equipment boxes themselves, with an internal BNC-SMA cable to
connect to the PCBs. So any signal going in or out would pass
via at least 4 BNCs, and 4 again if routed to another rack.
I often worried about this (since we mostly did equipment doing
very precise phase measurements etc.), but the HF 'old hands'
told me each time that I shouldn't.
For really critical stuff at 2 GHz and above they would prefer
SMA, and if things were really extreme the coax cables would
be replaced by rigid tubes, welded to the SMA connectors using
special HF induction welding equipment. SMA handles much higher
frequencies than BNC, but I don't think it matters for SDI.
question 3: i'm thinking of getting neutrik
isolated bnc connectors
(the d-type ones that are semi-recessed and thus well protected from
clumsy passers-by). but their soldering lugs break the coaxial
structure - cause for concern?
That could well be cause for concern. Is there really any advantage
to recessed BNCs ? The connector itself is usually solid enough,
and once a cable is attached to it the Neutriks are as vulnerable
as any other.
question 4: do i really want to solder hf stuff (even
though the
voltages are not too high), or will it unsolder itself eventually?
any recommendations as to procedures and tin?
Unsolder itself ?
Most BNCs today are crimped rather than soldered. If done using
the correct tools and procedure this should actually be better.
Ciao,
--
FA
There are three of them, and Alleline.
4:07 a.m.
On Tuesday, January 18, 2011 09:40:50 pm fons(a)kokkinizita.net did opine:
Hello Fons ;-)
And as long as its not what we here in the US call a 'Cambridge' connector,
which is a solderless install, you special strip the coax and literally
screw the connector onto the end of the cable. But its a time bomb whose
fuse could be as little as a couple of months long when install on a soft
foam cored cable. The cable cold flows and collapses away from the
connector shell and you have a very poor shield connection and crosstalk
you can see at the other end of the cable when there are 40 such cables
bound in a truck going 10 meters to another rack.
As long as the cable lengths were matched, shrug.
On Tue, Jan 18, 2011 at 10:59:59PM +0100, J�rn
Nettingsmeier wrote:
> * source
> * 5m or so of suitable cable
> * bnc wall socket
> * 20m installation cable (-63dB/100m @ 3ghz)
> * a ghielmetti patchbay (which includes two canare contacts to the
> patch cord and two bnc on the rear, unfortunately)
> * another 20m installation cable
> * bnc wall socket
> * another 5m cable
> * sink
Which is several reflections and a lot of vswr in a 75 ohm video circuit.
Why? Unless special ordered, the bnc connector you can by in 20 pound
bags, is a 50 ohm connector, and every one encountered in a 75 ohm video
circuit sticks up like a pocket combs teeth on a TDR.
The down side is that while there are 75 ohm bnc available, there is no
provision to prevent someone from plugged a 50 ohm connector into that 75
ohm socket. The 50 pin is too big for the 75 ohm socket and breaks the
female socket, expanding it so that a proper 75 ohm connector will likely
not even make a connection when its locked on. Here in the states, after
encountering lots of that sort of damaged sockets, I did find a src of 75
ohm bnc's but then had to go round up the right sized numbered drill bit
and a pin vice to spin it with, and drill out the back end of the pin in
order to get my fav 75 ohm video cables center conductor into the pin for
crimping.
Needless to say that makes for about 4x the time in installing the
connector.
My fav cable is Susan Clarks (Clark Wire & Cable) type 7559, its quad
shielded with both a silver plated 90% or so braid over a metalized mylar
wrap on the foam core for s shielding effectiveness of about 110 db, and
with its foam core, its both low loss and very very flexible.
question 1:
any hopes for reliable hd-sdi?
Can't really answer this. But BNC seems to be the standard
connector for this, so it's probably OK. question 2:
how can it be that a kick-ass company like ghielmetti
does not offer video patchbays that allow direct connection of coax
installation cables, but require rear bnc connections instead?
This is probably just a question of being practical. Wiring up
a patch bay to things outside the rack (or the equipment it is
part of) without connectors leaves you with something that is more
or less cast in stone. It can also be quite difficult to install.
I recently wired up a 96 point audio patchbay without rear
connectors (i.e. soldered), with almost all of the connections
going outside. Luckily these cables had the other end free and
didn't go into some wall. But I'll avoid to do that again...
I doing another one these days (the Sala dei Concerti - you know
the system needs some rewiring :-) but this time the patchbay has
rear connectors - it would be near impossible get it wired up
otherwise.
question 2b: is there an alternative for direct
rear coax
connection, thereby cutting out two potentially disruptive contact
surfaces?
Haven't seen it. When I was working at Alcatel, all HF racks we
constructed had back panels with double through-panel BNCs for
external connections. No external cable would ever be attached
directly to any of the equipment inside the rack. And more often
than not, the same through-panel BNCs were used on the actual
equipment boxes themselves, with an internal BNC-SMA cable to
connect to the PCBs. So any signal going in or out would pass
via at least 4 BNCs, and 4 again if routed to another rack.
I often worried about this (since we mostly did equipment doing
very precise phase measurements etc.), but the HF 'old hands'
told me each time that I shouldn't. For really critical stuff at 2 GHz and above they
would prefer
SMA, and if things were really extreme the coax cables would
be replaced by rigid tubes, welded to the SMA connectors using
special HF induction welding equipment. SMA handles much higher
frequencies than BNC, but I don't think it matters for SDI.
The secret is achieving a 'gas-tight' crimp. Not having the correct
crimping tool to do that leaves you with a time bomb with a years long
fuse.
question 3: i'm thinking of getting neutrik
isolated bnc connectors
(the d-type ones that are semi-recessed and thus well protected from
clumsy passers-by). but their soldering lugs break the coaxial
structure - cause for concern?
That could well be cause for concern. Is there really any advantage
to recessed BNCs ? The connector itself is usually solid enough,
and once a cable is attached to it the Neutriks are as vulnerable
as any other.
question 4: do i really want to solder hf stuff
(even though the
voltages are not too high), or will it unsolder itself eventually?
any recommendations as to procedures and tin?
Unsolder itself ?
Most BNCs today are crimped rather than soldered. If done using
the correct tools and procedure this should actually be better. Ciao,
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
She often gave herself very good advice (though she very seldom followed
it).
-- Lewis Carroll
12:39 p.m.
robin, gene, fons,
thanks for your replies!
On 01/18/2011 10:59 PM, Jörn Nettingsmeier wrote:
* source
* 5m or so of suitable cable
* bnc wall socket
* 20m installation cable (-63dB/100m @ 3ghz)
* a ghielmetti patchbay (which includes two canare contacts to the patch
cord and two bnc on the rear, unfortunately)
* another 20m installation cable
* bnc wall socket
* another 5m cable
* sink
gene, all bnc equipment used here is rated for 75ohms, and it is in fact
not so uncommon in studio and live audio technology (wordclocks, MADI,
video, pretty much anything except UHF antenna leads, which are the only
50ohm specimens in daily use here i can think of).
i will only use quality connectors (neutrik or equivalent) - no sense in
cutting corners there, most of the cost is work time anyways.
robin, we do have some conduits for later revisions, but they have not
been practical everywhere. i managed to squeeze a few dark fibers into
the budget, but otherwise we're pretty much set for the next 30 years
(which is why i want to make sure we can do 3ghz). there is also plenty
110ohm aes/ebu+analog cable and cat7, so i don't expect trouble for at
least the next decade or so. it's a music school, their investment
cycles are long and they won't be able to afford cutting-edge gear anyways.
question 1: any hopes for reliable hd-sdi?
question 2: how can it be that a kick-ass company like ghielmetti does
not offer video patchbays that allow direct connection of coax
installation cables, but require rear bnc connections instead?
fons, ghielmetti usually has multipin connectors on the rear, which
means you solder the cables to the connectors first, then plug, then
mount the patchbay. pretty handy. i guess they are not doing it for
video because their connectors aren't co-axial.
question 2b: is there an alternative for direct rear
coax connection,
thereby cutting out two potentially disruptive contact surfaces?
i think i'll go this route. i just have to find a product to fit the
small coax cables i have (the single strands in 5way-multicores). if
anybody knows a bnc crimp port for isolated mounting with washer and nut
(or, better yet, neutrik d-format for rivet mounting) that takes a
0.6/2.8 coax cable, let me know.
question 3: i'm thinking of getting neutrik
isolated bnc connectors (the
d-type ones that are semi-recessed and thus well protected from clumsy
passers-by). but their soldering lugs break the coaxial structure -
cause for concern?
fons, i had feared this would be an issue as skin effect kicks in. :(
need to phone neutrik about this, then :(
question 4: do i really want to solder hf stuff (even
though the
voltages are not too high), or will it unsolder itself eventually? any
recommendations as to procedures and tin?
gene, thanks for your valuable comments. i'm stashing this email for
when i'm older and less fearful. for now you have convinced me i don't
want to solder hf leads ;)
fons, sma is not really an option - too few mating cycles, too easy to
screw up for untrained people (since nobody's familiar with them), and
too time-consuming for patchbay use. but i'll keep it in mind for
permanent installations in places where stuff needs to be disconnected
occasionally for service.
best,
jörn
12:58 p.m.
On 01/19/2011 12:39 PM, Jörn Nettingsmeier wrote:
[..]
it's a music school, their investment
cycles are long and they won't be able to afford cutting-edge gear anyways.
Oh and I was already becoming jealous thinking you're planning your own
studio and was planning a trip to Essen to admire it..
just curious: Will there be any Linux-boxes inside or would those fall
in the "cutting-edge gear" category? :)
robin
21 Jan
21 Jan
11:36 a.m.
On 01/19/2011 12:58 PM, Robin Gareus wrote:
On 01/19/2011 12:39 PM, Jörn Nettingsmeier wrote:
[..]
unfortunately not :) but i do have an 8way multicore into the living
room and adat next door, if you want to admire that, i'll see to coffee
and beer :)
it's a music school, their investment
cycles are long and they won't be able to afford cutting-edge gear anyways.
Oh and I was already becoming jealous thinking you're planning your own
studio and was planning a trip to Essen to admire it.. just curious: Will there be any Linux-boxes inside or
would those fall
in the "cutting-edge gear" category? :)
probably not immediately. i'll try and convince them later, but i guess
it's going to be logic for now. but you never know, ardour has been
known to magically appear on machines i've worked with... from
ardour/macos, it's a small step into the light :)
cheers,
jörn
5050
days inactive
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days old
linux-audio-dev@lists.linuxaudio.org
11 comments
5 participants
participants (5)
-
fons＠kokkinizita.net -
gene heskett -
Jörn Nettingsmeier -
Robin Gareus -
Robin Gareus