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

[gene heskett]

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:
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