The issue for repeater receiver desense is the same basic issue that affects the bench test. For the bench test if the generator used for the adjacent channel signal has too much phase noise - that noise will degrade the receiver before the carrier level can be raised to the manufacturer's spec.
With a repeater - if the transmitter sideband noise is too great - or the duplexer's attenuation of that noise is insufficient - then the receiver will be degraded. Measuring the transmit carrier level at the receiver input - not so hard. Measuring the transmit sideband noise at the receiver input - not so easy. Your issue is probably due to not enough TX sideband noise suppression. We're assuming you used all double-shielded coax, but look at everything - maybe there is a faulty coax or connector allowing leakage to cause the degradation. -------------------------------------------------------------------- --- In Repeater-Builder@yahoogroups.com, Tim <tahr...@...> wrote: > > Hi Nj902, > > Well, I'm not trying to be exacting in the measurement, I'm just trying to > track down a desense issue in the system. I figured I'd look at how > the receiver does with the adjacent (transmitter) signal injected directly > into the rx input port. > > The spectrum analyzer hooked up to the RX port on the duplexer shows > -55dBm, which should be down sufficiently enough not to be heard by the > receiver. > > I'm running the duplexer into a dummy load, and all interconnecting > cables are > double shielded. > > However, the desense is so severe that I am beginning to think there may > be something wrong in the RX. Hence, the question. > > Just trying to find that silver bullet. Got any spares? > > Thanks, > > Tim >
