[Repeater-Builder] Recording of mysterious noise
Hello, Loaded sample to files section. Has anyone encountered this sort of noise on a system or have a suggestion as to what might be generating it? Proving difficult to determine source. Thank you, Doug - GM7SVK
Re: [Repeater-Builder] Recording of mysterious noise
It sounds like the squelch closes on your receiver when the signal drops, is that correct? If so, that would eliminate the possibility of the noise being the output of a repeater that has a tail timer. Can you detect any tail timer at all? If I were to make a guess, it sounds like a transmitter that is keying up with noise, such as an RF link for something, and noise on the link input is keying up the transmitter. Are you able to detect any PL tone in the noise that you hear? PL may give you a clue as to the source of the signal. Can you DF the signal? Is this in the ham band, or commercial freq? Does it happen more at certain times of the day? Is it weather related? A trick that I used was to set up a spectrum analyzer and watch 10-20Mhz at a time. I would listen to the noise and look for another signal that keys up at the same time. Very time consuming, but can be very effective. It's a crap shoot, but it beats just sitting and listening to the noise. Some ham rigs even offer a crude spectrum analyzer mode, such as my Yaesu VX7-R HT. I've used the VX7-R to look for signals with some success. (I had to read the manual to get the darn think out of the SA mode!) I used to do a lot of tracking down of interference. It helps to analyze what is not causing the noise and don't always focus on what you think it is. Eliminating what is not causing the interference many times helps you focus in on what is really causing it. Good luck and 73, Joe, K1ike On 6/29/2010 4:15 AM, gm7svk wrote: Hello, Loaded sample to files section. Has anyone encountered this sort of noise on a system or have a suggestion as to what might be generating it? Proving difficult to determine source. Thank you, Doug - GM7SVK
Re: [Repeater-Builder] Recording of mysterious noise
To me it sounds like either a system with intermod involving the repeater's transmitter getting into it's receiver, or similar to two repeater systems with one being on the reverse pair. I lean toward the first possibility. And if I were to guess, I'd say this is on UHF. If you shut off the TX while this is happening, does the noise disappear on the local RX? Chuck WB2EDV - Original Message - From: gm7svk specialq@ntlworld.com To: Repeater-Builder@yahoogroups.com Sent: Tuesday, June 29, 2010 4:15 AM Subject: [Repeater-Builder] Recording of mysterious noise Hello, Loaded sample to files section. Has anyone encountered this sort of noise on a system or have a suggestion as to what might be generating it? Proving difficult to determine source. Thank you, Doug - GM7SVK
Re: [Repeater-Builder] Recording of mysterious noise
Try dropping PL on the tail. Could be a signal mixing with your repeater offset and allowing your PL to keep your repeater receiver open. For example: 442.000 transmit with 100Hz PL + 5Mhz signal = 447.000 with 100Hz PL. Doesn't matter if you use PL or DPL - it still loops back in, and ham or commercial - on UHF they both use 5Mhz split. I have a 1250Khz AM station 1 mile from my site and its 4th harmonic is 5Mhz. Probably mixing somewhere locally; less when its raining (rusty bolt theory). I run PL decode and CSQ encode to keep this from happening, or split the PL tones differently. Of course its probably not the AM stations' fault, but as Joe said its better than listening to it. Tony On 06/29/2010 06:21 AM, Joe wrote: It sounds like the squelch closes on your receiver when the signal drops, is that correct? If so, that would eliminate the possibility of the noise being the output of a repeater that has a tail timer. Can you detect any tail timer at all? If I were to make a guess, it sounds like a transmitter that is keying up with noise, such as an RF link for something, and noise on the link input is keying up the transmitter. Are you able to detect any PL tone in the noise that you hear? PL may give you a clue as to the source of the signal. Can you DF the signal? Is this in the ham band, or commercial freq? Does it happen more at certain times of the day? Is it weather related? A trick that I used was to set up a spectrum analyzer and watch 10-20Mhz at a time. I would listen to the noise and look for another signal that keys up at the same time. Very time consuming, but can be very effective. It's a crap shoot, but it beats just sitting and listening to the noise. Some ham rigs even offer a crude spectrum analyzer mode, such as my Yaesu VX7-R HT. I've used the VX7-R to look for signals with some success. (I had to read the manual to get the darn think out of the SA mode!) I used to do a lot of tracking down of interference. It helps to analyze what is not causing the noise and don't always focus on what you think it is. Eliminating what is not causing the interference many times helps you focus in on what is really causing it. Good luck and 73, Joe, K1ike On 6/29/2010 4:15 AM, gm7svk wrote: Hello, Loaded sample to files section. Has anyone encountered this sort of noise on a system or have a suggestion as to what might be generating it? Proving difficult to determine source. Thank you, Doug - GM7SVK
