On some it does matter. You can not reverse the high and low and still have minimum loss for the pass frequency wanted. The notch is usually not symmetrical and it will have more loss on one side than on the other.
This problem is run into sometimes when trying to move one of those duplexers a long way from the design frequency. As you tune the notch a long ways the ultimate or best pass side (where there is minimum insertion loss) gets shifted to the opposite side from where it was originally. Most of those have an internal capacitor that you can't get to. 73 Gary K4FMX _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Danny Musten Sent: Tuesday, July 10, 2007 9:44 AM To: [email protected] Subject: Re: [Repeater-Builder] Notch duplexer dumb question I actually have seen those mobile duplexors labeled both ways, but commonly the labeling refers to what is connected. "Low" would be your 462 freq pass and would be tuned to reject 467. Most of those UHF mobile notch duplexors fairly broad banded and probably will not matter as long as YOU know how they are tuned. Danny KD4RAA On 7/10/07, George Henry <[EMAIL PROTECTED]> wrote: I have a Motorola TDN7407A notch duplexer (in reality, a Motorola-branded Celwave 633-6A-2N) that I want to use for a low-power GMRS repeater. The ports are labeled HI and LO.... now for the dumb question, do those labelings refer to the NOTCH frequency or the pass frequency? Unfortunately, it is not labeled with the current tuning, and I don't have easy access to anything to sweep it with.... George, KA3HSW / WQGJ413
