coax, wire, noise filters, bladder & grape juice

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From: Dan Schaefer <dfschaefer [at] usa.net>
Subject: coax, wire, noise filters, bladder & grape juice
Date: Tue, 15 Sep 1998 00:36:01
To: <lancair.list [at] olsusa.com>

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Boy! Always seems that a lot of stuff shows up over the weekends.

Here's my take on a bit of it.



For coax cable selection there are several things that must be taken

into account with the most important being the bulk cable's charac-

teristic impedance. For the radios we use in GA, most everything is

designed to use nominal 50-ohm cable. The many variations of RG-58

are all 50 to 53 ohm cable with the major differences in design, such

as solid vs stranded center conductor, jacket materials, dielectric

material, etc.,etc. Whatever you choose for your antennas, just be

sure the basic cable meets the ELECTRICAL requirements - the rest is

secondary. Personally, I like the RG-58A/U but that's just one of many

that are suitable. I prefer the stranded center conductor (a little

more flexibllity), with a solder-on (with screw-on back-shell), BNC

connector.



Something else to consider while on the subject of coax cables. Be

careful when spot-tying or clamping these cables. They can be damaged

(subtly) by muscling up on whatever method you choose to hold them

in place or to keep them from flopping about. The cable characteristic

so carefully built in by the manufacturer relies on, among other

things, the internal dimensions from the center conductor to shield.

Other things also have effect but you don't have much to say about

them once you've brought your raw cable home. So just don't see how

neatly you can tie those surgeon knots in the tie-string or how

tightly you can pull the zip-ties - you will squish the soft stuff

inside and degrade the cable quality. Even if it doesn't look too bad

at the start, the guts of the cable will cold-flow with a lot of pinch

and your transmission and/or reception quality will slowly get lousy

and you wont know why.



While on the subject of wire and cable, for standard hook-up wire, the

best to use is "Tefzel" insulated wire conforming to MIL-W-22759.

It's the best stuff to come down the road in a long time. Beats plain

Teflon hands down and Vinyl isn't even in the same universe.



And finally, to Dave Jones, I like your method suggested to get

vertical to pee - my only problem with it is that going straight down

at Vne + ANYTHING will most likely encourage me to empty other things

in addition to my bladder!!!! A discouraging thought to say the least.



Cheers,



Dan Schaefer





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