Joe, The fact that you have never, ever heard of this problem is interesting, because it is very common. In fact, the County of Santa Barbara had to make some major changes in their vast radio system to preclude the problems I mentioned.
The most common situation resulting in the unwanted turn-off code action is when a mobile in the coverage area of Repeater A is talking through distant Repeater B, while a portable (or weaker mobile) is using repeater A. Each time the mobile transmits, it captures Repeater A- blocking the portable- and then mutes Repeater A when it unkeys. Needless to say, this can be very frustrating to the portable user, especially when he cannot hear any voice from the other station. The same radio system also had a problem at one of the really dense sites, where every channel on both VHF and UHF used the same CTCSS tone, because the County made it their "standard." Due to various mixing and intermod products, many repeaters were being keyed without any valid input. Once the various repeaters were given different PL tones, the problems went away. As you pointed out, PL tones that are close to 134.4 Hz can cause inadvertent turnoff of CDCSS-equipped receivers. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of MCH Sent: Tuesday, August 28, 2007 6:58 PM To: [email protected] Subject: Re: [Repeater-Builder] Re: Subaudible Tones (Was subaudibe tones..) Fortunately, all are still using FM, so capture effect will not allow the repeater to see the TOC of the other weak user. I have never - ever - heard a false mute of a signal from the TOC of 'other users'. Before that happens, the repeater will lose the CDCSS code and will mute due to loss of code rahter than see a TOC. And even when that happens, the signal will come right back when it can see the valid CDCSS code. Aside from the above, what is the difference of what you described vs a repeater using CTCSS seeing the TOC as another CTCSS tone? It seems that should happen too if it can happen at all. Joe M. Eric Lemmon wrote: > > Before we embrace CDCSS as a cure-all, let us not forget that ALL standard > CDCSS codes use the same 134.4 Hz turn-off tone for muting. That means that > a mobile user keying distant repeater on the same frequency as yours, even > if using a different CDCSS code, will mute your repeater at the same time. > This is one of the "nasty little secrets" about CDCSS.
