In an attempt to address a hard 3rd order issue apparently being caused by a Motorola Radius repeater (no circulator and a cheapie internal notch "duplexer").
Background: Repeaters A and B share a properly engineered combiner system which is working well at 4 other sites. At this site a repeater we don't control (the Radius) shares the tower but NOT the combiner or antenna system. Repeater A transmits on freq X, Repeater B receives on freq Y, The Radius transmits on freq Z. The issue: 2X - Z = Y We believe the mix is happening in the Radius transmitter. We don't own or control the Radius and will need to "prove" the issue before we can get it's owner to address the problem. So... I tuned a spare can as a notch (~19db) at freq X and intend to place it in-line with the Radius in hopes of removing (lowering) the level of freq X getting into the Radius transmitter. A 20 dB reduction "should" reduce the intermod by 40 dB IF the mixing is happening in the Radius. I hope..... I intend to remove the antenna cable from the Radius, plug it into the T at the can and run a double-shielded cable from the can to the Radius. Does the length of the added cable matter? If so, what should it be: fractional wavelength at X or Z? Something else? TIA, Bill - WB1GOT
