[LAD] [OT] 3ghz coax and soldering...

[Jörn Nettingsmeier]

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