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

[Robin Gareus]

On 01/19/2011 03:39 AM, gene heskett wrote:
> 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

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.

> 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.

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.

> 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