To recommend what to do, the first thing is to determine which type of Q202G duplexer you have. Here is the manual on an older type that has the variable tubular dialectric to tune the notch. Eric Lemmon scanned this one and posted it for the group. Later types do not use the same technique to tune the notch.
http://www.repeater-builder.com/sinclair/q202-208-218-tuning.pdf In my case, I tuned 4 older duplexers down from the 160 mHz range to the ham band by changing the length of the coax coming from the cavity connector to the first tee from 10.5 to 12.5 inches. I only had to do this on the lower frequency pair of cans, as the high frequency cans tuned the notch with no change. This type tuning provides a notch both above and below the pass frequency. The band pass tuning did not require any change in harness at all. The only comment I have is the insertion loss seems to be a bit higher than spec when using the old 160 mHz harness. I get about 2 dB loss through the duplexer on both transmit and receive. Isolation is excellent. 73 - Jim W5ZIT --- wpp3 <[EMAIL PROTECTED]> wrote: > Read the posts here already and wish to clarify a > few things. First I > am in the process of converting a Q202G from the > 160mhz range down > into the 2m band, specifically 144.7500/145.3500Mhz. > I have found > that I will need to replace the harness to do this > as it will not tune > down that far. > > 1. I Understand I must make the harnesses at 1/4 > wavelength each > between the cavities and from the cavities to the > antenna "T" > connector. What is the formula for the exact cable > length? i.e. 1/4 > wavelength of freq * velocity factor of cable = > cable segment length? > > 2. Are the lengths exactly the same for the low and > the high sides or > are they dependent on individual frequency for each > side. > > 3. Where is the measurement taken? From tip-to-tip > of cable or from > center-of-T to center-of-T, etc? > > 4. In relation to #3 I will be using a > N-Male/UHF-Female adapter on > each can. Then connecting the "T" to that adapter. > Will this affect > the cable harness length calculations and if so how? > > Thanks in advance! > > Best Regards, > Bill - W4RVN > > ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
