I never understood either why 214 is quoted as 99% shield with it's 2 braids. I would think it would be 100% with lots to spare.
The 100% shield designation comes from having both a braid and a tape shield. The tape is theorietically the 100% shield and the braid is placed over it to act as a strain relief. The reason it desenses it's self is the dissimilar metal condition the the tape presents to the braid. The power from the transmitter creates "Micro arcs" in between the shields and bounces around like pac-man. You can use it for the cables to and from the duplexer, but running power down the wire creates the arcs so you get a general rise in the noise floor when trying to recieve back through it. Using this type of cable for the antenna run is a sure way to get kicked off a mountain top. Take a look at standard cable guy issue RG-6. This is a prime example of coax not to use. The tape is 100% coverage, Then that is covered with 25% - 60% braid depending on how cheap your cable company is. It gets better, The center conductor "Stinger" is copper clad steel, this has been a RF nightmare from the get go as tempreture changes. Try doing a google search to find the different tempreture expansion and contraction rates of materials and compare them. Over several years the steal to copper bond breaks with tempreture and user movement and the microfractures will create noise in the coax, especially when moved. But it is cheap so who cares? The only saving factor is that both the braid and tape are aluminum, you can't solder a connector to it to save your life, but you can crimp all day long. Then you have the problem of the sucked fitting which will attenuate signal below 100MHz but pass everything else fine. And there are impedence bumps if the coax wasn't rolled right. To answer another question, the braid of the Flexi took the solder, the tape shield did not. I held the connector upright and dumped an ass load of solder down the holes so it got the threads of the connector all nice and goopy. And yes, I will admit to buying the $5.20 each silver plated teflon connectors from the local Radio shack. But when you are down and out on a holiday week-end, you have to make "Sacrifices". "Scott" <[EMAIL PROTECTED]> wrote: >Thanks All----Sounds like I'd better go with some sort of hard line for my >between unit RF interconnects to keep between cable leakage to tolerable >limits----and probably noise too. But this brings up another issue: forgetting >about noise for the moment ---how can a 214 type cable which is listed as >97-98% shielded have lower leakage (desense problems) than a foil cable listed >as 100% shielded? > >The big question-------what is the most economical combination of small >diameter hard line and an "N" compatible connector assembly?--------is there >something that can be done with say 1/4" superflex and the affordable solder >through the holes teflon "N" connector that is similar to the 259 "UHF" >connector?----what is the best way to go? > >And another-------I've seen military microwave gear interconnected with >hardline less than 1/4" diameter ---smooth tubing---with soldered on "N" >connectors-----like is used in mobile helical duplexers-----is this system >suitable and where does it come from? > >Thanks much, 73 >Scott, N6NXI > ----- Original Message ----- > From: Scott Overstreet > To: Repeater-Builder@yahoogroups.com > Cc: Scott Overstreet > Sent: Saturday, November 27, 2004 5:44 PM > Subject: [Repeater-Builder] Coax Question > > > OK guys ---I hear you all saying that hard line is better but none of you > have said what is the actual problem with 9913 flex or LMR-400. In other > words---What is wrong with a quality foil under braid "100%"shielded foam > cable and I'm assuming use between receiver and duplexer, transmitter and > duplexer and duplexer and antenna? > > And then the next question that follows is that inside a cabinet full of > stuff where 1/2 inch hard line is just to stiff -----what do you suggest > ---and in this case assume that we are talking about three or four > repeaters----yes, receivers, transmitters, isolators and duplexers all in the > same rack cabinet? > > Scott > N6NXI > > > > > > > > >------------------------------------------------------------------------------ > Yahoo! Groups Links > > a.. To visit your group on the web, go to: > http://groups.yahoo.com/group/Repeater-Builder/ > > b.. To unsubscribe from this group, send an email to: > [EMAIL PROTECTED] > > c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. > > __________________________________________________________________ Switch to Netscape Internet Service. As low as $9.95 a month -- Sign up today at http://isp.netscape.com/register Netscape. Just the Net You Need. New! Netscape Toolbar for Internet Explorer Search from anywhere on the Web and block those annoying pop-ups. Download now at http://channels.netscape.com/ns/search/install.jsp Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
