19 Jan
2011
19 Jan
'11
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