Been following this thread for a while, some thoughts in random order: If I remember correctly you said that you are using the 1 5/8" heliax notches as your duplexer. If I also remember correctly others have reported problems of many sorts with these homebrew devices.
While not an easy thing to find I would suggest that you most likely need some sort of a bandpass cavity on the receiver to protect from the noise that gets past the heliax notches. Remember that a notch duplexer only removes the notched portion of the TX signal on the RX side and the RX signal on the TX side, all other noise is passed directly to the load. Thus you only have two small notches, one at the RX frequency and one at the TX frequency. Everything else is passed. You probably should also look at the TX signal to check for spurs. If the RX has the extender circuit installed, turn it off and rerun your test. It could be that the extender is tuned to a frequency near the TX or a low level output from the TX. I also have had duplexers that look good with a tracking generator but fail under TX power. Milt N3LTQ Quoting Tim <tahr...@swtexas.net>: > Hi 902, > > Understand about the sideband noise, but I figured at a MHz away, it > probably wouldn't be an issue. Getting the same performance out of > both sides of the duplexer ... about 102dB notch & 1.5dB attenuation. > > Using RG142 for all interconnects, except from TX/RX to duplexer, and > those are RG-214. > > Guess I could hookup a signal generator with a -50dBm signal into the > RX, and measure it at the input with a high impedance probe hooked to > the spectrum analyzer. Take that measurement, and then hook up the > duplexer & key it up. Check the measurement again & see if it's the > same, or more. > > Thanks, > > Tim > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
