> "kerincom " <kerin...@...> wrote: > Hi guys .I am just wanted to confirm a question on > coax shielding .
Simple answer... It's there and never seems to behave exactly how you would expect it to. > With 2-10 watts transmitting through rg213u could RF be > escaping that could cause desensitization to other radios. RF can escape through some types of hard line (believe it or not). There always will be local area RF around, just a question of how much is coming through/from the coax braid and what if any grief it may be causing. If you're working at the 2 to 10 watt (what many of us assume is a fairly low) power level and you've got desense gremlins, smart money says you probably (also) have other or additional issues to deal with. > The repeater I have setup uses 9 meters of heliax from the > main diplexer to ant and rg213u from the link radio to its > antenna. Nothing wrong with RG-213u especially when compared to other possible choices like someone using RG-58au. Just a question of loss per length and your preference with the end result values when you use/install it. > I am finding I am getting problems with the link transmission > interfering with the repeater rx. The link antenna is a yagi > 3 meters above the ground and the main repeater antenna is 6 > meters above it. So do some testing... put a termination (dummy load) on the end of the feed-line (regardless of the type you're using) at the Link-Yagi end. See if the problem goes away when you've got the Link Radio (transmitter) working at full power into the test termination (load). > I am currently trying band pass cavity on the receiver rx or > band pass/band reject diplexer with some success but I am > wondering if the rf escaping from the cable is causing > problems inside the repeater shed even at a low wattage. The proper type and placement of cavities will help, but you should first consider the Link Tx Termination Test I mention above. You don't yet know where the problem really originates from and you don't mention what type of repeater receiver you're using. Should we assume it's something of decent quality and that you have it properly protected. And what's the repeater transmitter doing when the link is active? Do you make the classic mistake of tie-wrapping the feed lines into one big bunch? > I am definitely changing the rg213u to either rg223u or lmr400 > as it is only on the link radio and shouldn't have any effect > on the repeater's operation. Please... If you feel you must change the feed line, don't use any LMR type of coaxial line or you'll be wasting your and our time with additional problems. LMR-400 is not good coax to use in and around duplex (repeater) radio or any high adjacent RF environments. > Has anyone else had the same sort of problem where the rf > energy leaks out of the cable in the shed and causes problems > to the repeater and they had to upgrade the link cable to > 100% coverage cable You're not yet sure that's the problem and I'll bet the coax shielding value is not the large problem contribution you think it is. We'd need to know more about the radios, antennas, power levels, receiver and transmitter filtering (what we call "Duplexer") or pre-selectors and notch cavities you might have around. Even though you're running RG-213u, it's not the best but when applied in modest length runs it's not the train wreck you might think it is. And you're on the bottom side of the earth in Auzzie Land so we have to flip the computer screen upside down to read your posts, but that's relatively easy. :-) > Thank You, > Ian Wells, your turn, s.
