At 1/20/2010 21:40, you wrote:
>I thought I d better update the list on what was found. First off, the >entire repeater was taken in to the shop for exhaustive testing. The can s >were taken apart, inspected and cleaned. All that was visibly found was a >little carbon. The two service monitors showed they were working ok. But, >when placed back into service at the site, the transmit side leaked into >the receiver side. It presented a crackling noise, like saran wrap being >crushed. I don t know if the technicians tested the repeater at full >power, ( 110 watts) during testing, but I think so. > >We did solve part of the problem. A fifth can was put into line, on the >transmit side and by golly, it did the trick. The repeater is sounding >better than before the strike. This actually points to an antenna system problem. I know in an earlier post that you said you checked the antenna system & it was good. However, unless you took a different repeater/duplexer to the site & connected it to your antenna & there was no desense, you don't know that it's good. The VSWR can check out fine, but it can still be totally unusable for duplex service as a result of lightning damage. I have at least 3 such antenna systems that fit that description. The pass cavity you added is removing more phase noise from the TX. Less phase noise available to convert to your input by the nonlinearity in your antenna system means less desense. I also used this method to cure a desense problem in an antenna system that couldn't be accessed at the time. Bob NO6B
