Re: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference
Its called adjacent channel rejection, if your unit is not properly aligned this can occur. PL or not if its poor on rejection then you get bleed over, the same kind of thing that happens when a trucker goes by pushing excessive wattage from his CB and bleeds all over a poorly shielded amplifier or TV. This can also be a result of the shielding of your feed line to your repeater being compromised. These symptoms also cause desense on the receiver. Best Regards, Chris Carruba (WQIK389) CompuTec Data Systems Co Administrator irc.spidernet.org http://www.spidernet.org «§» Amateur Radio Programming Discussions RSS files «§» /server irc.spidernet.org /join #radio-prog From: ptt_pupil [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, November 18, 2008 1:30:26 PM Subject: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference Can anyone tell me if there are ANY fixes for co-channel interference? What is the use of a PL tone if it isn't able to block out the co- channel users? Is it because the co-channel user is transmitting with more power and is able to break the PL tone? What are the expectations of a PL tone? When does it work and when does it not work? Are there other devices that can help all? Thanks in advance!
Re: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference
ptt_pupil wrote: Can anyone tell me if there are ANY fixes for co-channel interference? What is the use of a PL tone if it isn't able to block out the co- channel users? Is it because the co-channel user is transmitting with more power and is able to break the PL tone? What are the expectations of a PL tone? When does it work and when does it not work? Are there other devices that can help all? Thanks in advance! hmmm...sounds like someone needs to read up on how CTCSS works... If someone else on the channel is using the same tone, you will hear them. (And as someone mentioned, some decoders are better at rejecting adjacent tones then others.) If there is someone on the same tone, and they were there first, your only option is to change tones. I'm assuming you're on a commercial system (hence the 450-460 in the subject!) Frequency sharing is the norm there, and if there is someone else on the same frequency as you, you just have to learn to share. If it's a community repeater with several tones turned on, you'll just have to turn that tone off, and maybe pick another if there's a user there, and reprogram their radios.
Re: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference
For some PL decoders, a weak noisy signal will trigger the PL detect and let the signal through. On the other hand, if the co-channel signal happens to be using the same PL tone, it will get through also. A good PL decoder like the TS-64 will rarely false. I have a repeater configured so that either a quiet (20 dB quieting on a SINAD meter) or the correct PL tone will trigger the repeater. I tell users that if they are having problems holding the repeater to use the PL tone to extend their receive range. The PL decoder in my Zetron 38As will detect the tone and key the repeater when nothing but noise is heard on the output. I have to combine the PL with the COS to get normal operation from this setup. If you are using one of the older PL decoders such as one normally used in a mobile radio, I would suggest changing to a better decoder, like the TS-64. It will also encode and decode at the same time, saving having to install a separate encoder in a repeater. 73 - Jim W5ZIT --- On Tue, 11/18/08, ptt_pupil [EMAIL PROTECTED] wrote: From: ptt_pupil [EMAIL PROTECTED] Subject: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference To: Repeater-Builder@yahoogroups.com Date: Tuesday, November 18, 2008, 12:30 PM Can anyone tell me if there are ANY fixes for co-channel interference? What is the use of a PL tone if it isn't able to block out the co- channel users? Is it because the co-channel user is transmitting with more power and is able to break the PL tone? What are the expectations of a PL tone? When does it work and when does it not work? Are there other devices that can help all? Thanks in advance! ,_._,___
Re: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference
You left us with very little information about the problem. I'll make the assumption that the co-channel signal is relatively distant and weak. Assuming that the co-channel signal is not transmitting the same tone that you are using, your receiver should not open. If your receiver is opening, and you are sure that the distant station is not transmitting the same tone, you either have a faulty decoder or it is configured incorrectly (often the hookswitch will be to blame for inexperienced users). If you are a commercial user, there should be a microphone hookswitch. When you remove the microphone from the hookswitch, the decoder allows any signal to get through until the microphone is hung up again. Now, if the interfering signal is very strong, then it will capture your receiver and block weaker signals from getting through. Chuck WB2EDV - Original Message - From: ptt_pupil [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, November 18, 2008 1:30 PM Subject: [Repeater-Builder] 450-460mhz Repeater Co-Channel Interference Can anyone tell me if there are ANY fixes for co-channel interference? What is the use of a PL tone if it isn't able to block out the co- channel users? Is it because the co-channel user is transmitting with more power and is able to break the PL tone? What are the expectations of a PL tone? When does it work and when does it not work? Are there other devices that can help all? Thanks in advance!
