OK to use TV coax for microphone?

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I believe coax for TV is universally 75 ohms, but there are certainly
more than two impedances available.

I see 32, 50, 51, 51.5, 52, 53.5, 73, 75, 80, 93, 95, and 125 ohm
cable at:

http://www.belden.com/pdfs/Cable101/coaxrefc.pdf 

JF

On an old TV antenna I used 300 ohm Shielded Permaohm. Shielded twin lead. I don't see it being made now.

greg

For htZt length of coax the connectors probably would be of more concern. Are they alerady fitted, or ary you going to attempt that yourself? Are they of the proper type (diameter, keying, impedance) to match your equipment?

etc.

Twinax, for example.

Yo, Arny, please don't feed the trolls. Nobody believes that tripe from Allison, it isn't worth even responding to him.

don't see it

--- I vaguely remember seeing something like that. I don't know how far back, but I never used it.

The last time I did TV stuff of any consequence I'd just gotten married and we were living in an apartment in New York, in the Bronx, and our TV reception was a mess (rabbit ears on top of the TV) of ghosts because of multipath reflections from the buildings around us.

I'd just read about log periodic antennas and how nicely broadband and directional they were, so I decided to build one for the TV band from the instructions in Popular Electronics (or one of the other hobby mags), and after scaring the shit out of my wife with this not inconsiderable structure growing and coming to life in our living room, eventually got it installed on the roof of our building with the blessings of our landlord.

Varnished wood and wire and, as I recall, 300 ohm twinlead leading down to our TV.

Then I had to build an intercom so that as I adjusted the antenna in azimuth and elevation, my wife would say "better" or "worse" as I pointed the antenna. Eventually we zeroed in on the best picture we could get and got rid of most of the ghosts.

Thanks for bringing back those memories. :-)

JF

"Arny Krueger" "Phil Allison"

** ROTFL !!

- that is proof only that there are folk who sell microphones !!

IMBECILE

** Err - that is a shielded twisted, pair cable.

Not co-axial cable at all.

IMBECILE

..... Phil

"Richard Arse Licker Crowley"

** God Almighty -

what a low life, autistic scumbag this human turd is.

.... Phil

Never saw any twinax in the mainframes. The standard was "trilead" (signal with two grounds connected to a "tuning fork" connector that slipped over the signal pin and ground rail) and later high-speed trilead (Gore-Tex insulation) and sometimes micro-dot coax for clocks. They used both 50ohm and 90ohm varieties. ...and piles of it!

--
Keith

only

AS400 ain't a mainframe. ;-) It's made by those wheat farmers on the tundra; never seen one.

--
Keith

--- You're right, of course, since only the single center conductor of _coaxial_ cable can be congruent with the axis normal to the cross section of the shield.

But I'm interested...

It's not like you're stupid, you know,

Far from it, sometimes you come up with perfect solutions for posted problems, so why do you find it necessary to abuse your lessors?

JF

"John Fields" "Phil Allison"

** Such flattery will get you no-where.

** I very often do - regardless of what the idiot, trolling OPs think.

** Have you stopped beating your wife?

BTW

have you seen the complete trash "Arny " put in his reply to my points ?

Why don't YOU inform the several NGs how wrong it is ?

Your silence = approval.

...... Phil

I've seen several... inside of IBM buildings. :-)

It's actually a pretty neat machine in many ways with one of the most "modern" operating systems available: Linux and the Mac OS trace their roots to UNIX, and Windows comes from Dave Cutler who also did VMS -- both back in the '70s, whereas OS/400 was written from scratch in the late '80s and benefitted from everything that had been learned in UNIX and VMS. Of course, UNIX and VMS have evolved as well, but there are certain fundamental aspects that will always remain, such as the UNIX "everything is a file" design decision.

---Joel

Thank you for adding to my store of knowledge.

He thinks he is earnest. Most of these effects do occur in some applications. If you have read the whole thread you will have seen even more other use case issues. Not all of which apply to your use. Kevin's biggest problem is that he does not know what the boundaries of applicability are of the various things he thinks he understands.

In general, it will work OK for low fidelity / casual use. It will not work well, and it may be a reliability problem. Forget about it for good amateur or serious use.

Now if there were more that only one minor competitor.

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Not at all flattery, just a simple statement of fact meant to
underscore that your anti-social antics aren\'t due to stupidity.

Phil seems to live in an alternative universe where pedantry is the rule.

--

..and everybody else isn't.

It was not a common usage.

In the 80s IBM tried to popularize a technology called "Token ring", which worked over twinax. Token ring hardware was made for use with mainframes, but it didn't gain much acceptance in the marketplace.

The 8100 series of minicomputers, and the sequel System 3 and 36 systems relied more heavily on token ring, so people who worked with these smaller computers were more familar with twinax. Been there, done that.

Eventually, the larger system 3 computers were upgraded to the point where there was not a lot that would distinguish them from mainframes.