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 >
