If the VF is different, then the lengths would need to be recalculated. The factory cables use MIL-spec RG-214 (double shielded, silver-coated), with crimp-on male N connectors, and the lengths of the new cables I got matched the lengths in the table of jumpers RFSystems sent me. When I made my own to the lengths specified below, the duplexer worked just as well as with the factory cables. It's hard to argue with success.
When you have over 100dB of isolation/rejection, you want all the shielding you can get, so RG-214 is the way to go (compared to RG-8). Bob M. ====== --- "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > I'm assuming that if the old RG-8 cables are being > replaced with RG-214 cables that are the same > length, that the velocity factors of both types of > cable are the same..... > > -----Original Message----- > >From: "Bob M." <[EMAIL PROTECTED]> > >Sent: Dec 19, 2005 7:10 PM > >To: [email protected] > >Subject: Re: [Repeater-Builder] Re: Old duplexer > tuning question > > > >New cables will be a lot more flexible, and with > >RG214's double shield, they should work better too. > >It's tempting to use the coax and TEE fitting as a > >handle when picking the unit up - don't do that ! > > > >I found that the connectors added exactly 1/2 inch > to > >the cable length PER CONNECTOR, so you would want > to > >cut the coax 1 inch shorter than the final lengths > of > >11-1/2 and 12 inches. I solder the center pin, > rather > >than crimping it. > > > >Not too many analyzers will be able to go down to > the > >100+ dB that these duplexers are capable of > providing. > >That's one reason why they tell you to tune each > >section separately. I did find that if I use my > signal > >generator at a fixed frequency, rather than the > >sweeping tracking generator, I can tune the > spectrum > >analyzer to the same frequency and crank down the > >filters. I can barely see the sig gen around 120dB > >down or more, on the final configuration. > > > >As others have mentioned, if your equipment does > not > >provide a good 50 ohm impedance, you should use > 6-12dB > >pads on each line connected to the section you're > >tuning. Of course, adding this attenuation pushes > the > >signal even further down into the noise, but it > should > >not be a problem on any single section. Use as much > >signal from the tracking generator as possible > (i.e. > >+10dBm or more). > > > >The resulting notch from the entire duplexer will > >appear to be quite wide, even though the individual > >section notches are quite narrow. > > > >Good luck with it in the morning when it's warmer. > > > >Bob M. > >====== > >--- tony dinkel <[EMAIL PROTECTED]> wrote: > > > >> All, thanks very much for the input. I was > already > >> in the process of > >> rebuilding the interconnects to RG-214 with crimp > on > >> RFS connectors as > >> a punt. That old RG-8 was hard as a rock. > >> > >> I also think my problem with the notches is that > I > >> do not have enough > >> dynamic range on my ifr 1600 to see the bottom. > It > >> works ok on the > >> individual cavities but once I combine the whole > >> circuit thats when it > >> mushes out. > >> > >> I think I will get this thing knocked out in the > >> morning. This place > >> is getting dark and cold. > >> > >> Thanks, > >> > >> td > >> wb6mie __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
