Shanon, I'm fwding this for info.
On Nov 27, 2009, at 5:19 PM, Allan Boyd <ve3...@vianet.ca <mailto:ve3...@vianet.ca>> wrote: > > > Greetings Tony; > > Well after reading your e-mail let me know you > are not alone with this problem with desense with > the Icom D-Star 2 meter repeater. Our D-Star > machine had the exact same problem when we first > put it on the air. We had a 4 can duplexer with a > high band pass cavity that was operating on a 60 > watt analog repeater (GE Master II) with no > problem at all. Once we put the D-star machine up > on the same frequency same antenna and duplexer, > cables etc the only thing that changed was the > repeater was desense to the hilt. Tests showed we > had about 85 db isolation. Like you we tried many > things and troubleshooted everything else knowing > that the duplexers were good. After much head > scratching we finally learned through Icom rep > that the D-Star Icom IR-RP2000V needs at least a > minimum of 90db isolation and I say 90db at the > very least. We finally changed out the 4 can to a > 6 can Sinclair res lock duplexer with a 100 db > isolation and all I can say is WOW what a > difference. The desense disappeared and the > D-Star repeater now way out preformed the analog > repeater we had up, it works amazingly because of > the extra isolation. As you are aware the front > ends of the Icom machine are not the best and > leave a lot to be desired we learned the rule > with this model repeater the more isolation you > have the better you are. It worked fine for the > analog system with the GE master II however once > we went digital we needed the new set of cans up from 4 to six. > > Now I am not saying that this may be your problem > but by your e-mail it certainly sounded like my > complaint earlier in the year. Good luck. > 73 > Al > VE3AJB > Trustee VE3RXR Stack > Ontario Canada > > At 01:26 PM 27/11/2009, Radioman wrote: > > > > > >well to start with the outside signal is garbled up until i switch to > >low then the user clears up, when switching back to hi he gets garbled > >up again and when the user unkeys i here 2 seconds of robotic noise, and > >the robotic noise does not happen on low. > > > >i think that clear enough desense, with the tracking gen i have 86db of > >isolation in the 4 pack cans > >not perfect, but really not bad i also use a 10'' 3foot high band pass > >cavity set to 1 db of loss and it gives me aprox > >20db at 500khz window on my rx freqency > > > >honestly i don't think you could ask for any better then that, but the > >desense sounds like i have no duplexer's > >and I'm starting to point at the poor construction of this over sized > >empty box and shielding mobile radios give you > > > >Tony > >NN1D > > >
