Perhaps I should explain this a bit further.... R.F. energy travels along the surface of conductors. Shields have two surfaces where R.F. energy can travel whereas the simple conductor has only one such surface. The "second" surface of shields not properly accounted for is where "problems" often reside.
There are whole chapters of engineering text books devoted to this subject and this is merely a short and simple set of email ramblings, but rest assured that shielding can be a real pain in your rear for the reason touched upon in these emails. And the complex impedance presented at any specific point along the shield and the calculations involved to properly consider these values are not so simple a matter as the other, un-shielded, scenario where one merely shunts r.f. energy at the connection points of a simple un-shielded twisted pair. Very best regards; - Bob Finch On Wed, Mar 27, 2013 at 10:32 AM, w9ya <[email protected]> wrote: > I'd have to look at the circuit in more detail to be assured of this > v/v the altus metrum fligh units, but generally the need for shielding > in the wiring looms is over-rated and further the shielding can act > like a parasitic antenna where twisted (specifically by pairs) wiring > would not otherwise be a problem. > > Very best regards; > > - Bob Finch > > On Wed, Mar 27, 2013 at 10:28 AM, w9ya <[email protected]> wrote: >> Um....I use the following; >> >> 1 - Properly routed and supported *stranded* wiring. i.e. NO >> unsupported flexing of the wiring loom. >> >> 2 - Tinned (with solder of course) wiring is specifically indicated. >> It will not release from under the screw terminal when the terminal is >> properly tightened and supported. >> >> 3 - Double check the connections before each flight; by making sure >> the wiring and screw are snug AND that the wiring is still routed and >> supporteed correctly. >> >> YMMV of course but I preclude intermittent continuity issues resulting >> from the lack of a gas tight ferrule connection. >> >> Very best regards; >> >> - Bob Finch >> >> >> >> On Wed, Mar 27, 2013 at 8:16 AM, Thomas Müller >> <[email protected]> wrote: >>> If you like to attached stranded wire to screw terminals you should crimp >>> the ends in a ferrule. Tin soldering is not a good idea since the thin is >>> pretty soft and flowable which might lose the connection. >>> >>> >>> >>> Thomas >>> >>> >>> >>> Von: [email protected] >>> [mailto:[email protected]] Im Auftrag von Clay & Carly >>> Dunsworth >>> Gesendet: Mittwoch, 27. März 2013 14:59 >>> An: Altus Metrum >>> Betreff: Re: [altusmetrum] wires >>> >>> >>> >>> I have always steered away from the solid core. Most of the time where >>> space isnt critical ive used machine tool wire, but doesnt work with the >>> "smallness" of the Altus Metrum products.(16ga). I bought some smaller 26ga >>> stranded, becuase another altimeter i have, the MFG suggest 26ga stranded as >>> the "smallest" wire that would be safe. this was after I discovered blue >>> color on the copper of the ematch leads. (now i suspect chemical reaction of >>> the bare copper, oily fingers, and BP residue.) Oddly its almost too big for >>> the TM i have. >>> >>> >>> >>> I have never tinned the ends of my wires, but the belkin cable i cut up the >>> other day suprised me that the wires were stranded copper, and seemed >>> suitable for this. I always envisioned they were like old telephone cable >>> with that fiberstuff, that would be unsuitable. Maybe with this small of a >>> gage i should solder tin the ends for added reliablity? >>> I have litterally hundreds of feet of the stuff, and would be a "freebe" for >>> the rest of my av-building life. >>> >>> >>> >>> Clay >>> >>> I guess thats why we test! >>> >>> On Tue, Mar 26, 2013 at 10:41 PM, Michael Stephens <[email protected]> >>> wrote: >>> >>> My only worry would be that solid core wire doesn't like vibration very much >>> but stranded wire doesn't do well in screw terminals. I would think it could >>> definitely handle the voltage, especially since its such low duty cycle. >>> >>> On Mar 26, 2013 8:16 PM, "Clay & Carly Dunsworth" <[email protected]> >>> wrote: >>> >>> Anyone use cat5e cable for thier avionics bay? >>> >>> Making a small launcher for the kids, i noticed the 4 twisted pair i >>> have would be a good match for my bay? >>> >>> Its good for things like telephones and data signal, but what about >>> ematch voltage? >>> thinking the sheething and twisted pair may be good at RF shielding? >>> Clay >>> >>> _______________________________________________ >>> altusmetrum mailing list >>> [email protected] >>> http://lists.gag.com/mailman/listinfo/altusmetrum >>> >>> >>> _______________________________________________ >>> altusmetrum mailing list >>> [email protected] >>> http://lists.gag.com/mailman/listinfo/altusmetrum >>> >>> >>> >>> >>> _______________________________________________ >>> altusmetrum mailing list >>> [email protected] >>> http://lists.gag.com/mailman/listinfo/altusmetrum >>> _______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
