Same CTCSS (PL) codes can and sometimes do contribute toward some very weird repeater and site mix problems. If you look at a spectral display of a busy repeater site... you'll often see a lot of oscillators, injection chain signals, microprocessor signals, yadda, yadda. When the wrong combination of signals mix, you end up with a gremlin.
Keep in mind that using a different CTSCC/DCS Code won't fix a bad mix or a gremlin, but it can and will sometimes "mask it" so it's not an "in you face" problem. If there's an interfering mix blocking your receiver, your system operation will still suffer. Relative to grand scheme of things... it's a great idea to go with a different CTCSS/DCS (Signaling) code in busy locations. But also keep in mind... if there's a real serious problem... you'd probably want to know about it if a gremlin signal is causing grief. s. > "Jim Cicirello" <ka2...@...> wrote: > > I can tell you that the same tones on different frequencies inside the same > site can cause a problem. My 2-meter repeater was on 151.4, the same tone as > the local high band fire and channel on the VHF community repeater. When a > combination of the units with 151.4 came up, I had inter-mod on my 2-meter > machine. Also at times there was noise on the fire that we could tell > disappeared when the 2-meter dropped along with the community repeater. > Luckily I own the tower so I was able to move my 2-meter repeater to 123.0 > and it happened that my private channel on the community repeater was also > 151.4 which I also changed. Now I try to make sure that every PL inside my > site is different. Since there is NO two PL's the same, the problem went > away. Our Motorola Tech told me this is common at tower sites using the same > PL on different frequencies. > > > > 73 JIM > > > > From: [email protected] > [mailto:[email protected]] On Behalf Of WA3GIN > Sent: Sunday, August 30, 2009 9:07 AM > To: [email protected] > Subject: [Repeater-Builder] Nearby Repeaters > > > > > > Looking for opinions. > > > > Our club has a couple of 2m repeaters; we chose to run them with PL and we > picked 107.2 because that tone freq. was not in use in the area. Recently > two other clubs who also have 2m repeaters have decided to utilze the same > PL tone freq. > > > > Does having numerous repeaters PL'd with the same tone freq. increase the > probability of the normally generated intermod/mixed signal to now carry > within the produced signal a correct PL tone that may land on the input > freq. of another local repeater? Is it considered a bad practice to utilize > the same PL for numerous repeaters in the same band all located within a few > miles of each other? > > > > Thanks, > > dave > > wa3gin >
