Only 10 dB ??? Neil
---- Original Message ---- From: [EMAIL PROTECTED] To: [email protected] Subject: Re: [Repeater-Builder] That horrible noise Date: Fri, 21 Apr 2006 09:40:34 -0700 >Scott, your math is off by +10dB. > >On 4/21/06, Scott Zimmerman <[EMAIL PROTECTED]> wrote: >> Guys, >> >> I think you're missing one detail here. 146.73 minus 146.85 is 1200 >KHz. >> Twice the >> typical 2 meter split of 600Khz. >> >> I'm not sure EXACTLY why it's happening, but the math here has BAD >written >> all over it. Anytime you deal with multiples of your input to >output >> frequency separation, it's not a good thing. >> >> I wonder if the two repeaters are using the same PL tone? If so, >does one, >> or both encode that tone as well? >> This could help explain putting the repeater in PL not helping to >eliminate >> the interference. >> >> I think Ken is on the right track with an audio delay causing a >howl. It's >> not a necessity however because of the RF delay in the possible >feedback >> path. Realize that even at the speed of light (in free space) RF >> transmission and reception are not instantaneous. >> >> I think your best bet is to find a different frequency or location >for one >> of the repeaters if possible. >> >> Scott >> >> Scott Zimmerman >> Amateur Radio Call N3XCC >> 612 Barnett Rd >> Boswell, PA 15531 >> >> ----- Original Message ----- >> From: "Ken Arck" <[EMAIL PROTECTED]> >> To: <[email protected]> >> Sent: Friday, April 21, 2006 11:24 AM >> Subject: Re: [Repeater-Builder] That horrible noise >> >> >> > I'd be interested in hearing the wav file you recorded, Dave >> > >> > But bear in mind that your comment that it's not coming from >either >> > repeater could easily be wrong. As a matter of fact, if you're >running a >> > delay in the audio path of either repeater, one of them is most >definately >> > involved. It sounds like a typical spur/mix/intermod issue to me, >probably >> > involving a 3rd party. >> > >> > Anyway, let's have a listen. >> > >> > Ken >> > >> > At 02:55 PM 4/21/2006 -0000, you wrote: >> >> >> >> >> >>Two VHF repeaters in town have been bothered by this from time to >> >>time.. The first, which only occasionally gets it, but gets it >LOUD >> >>when it happens, is 146.730- The second (mine) at 146.850- is >> >>getting it almost continuously now, but weak, ranging from "will >> >>open squelch" (even with PL!) to "Will hold squelch but won't >open >> >>it" Unfortunately, it's putting enough energy out at low >> >>frequencies that the PL board is seeing a tone, so PL won't save >me. >> >> >> >> >> >>The noise has an echoing quality that I think is VERY >distinctive, >> >>but I can't figure where it's coming from. >> >> >> >>It's not happening in either repeater, we've had the opportunity >to >> >>completely shut down the machines when it's happening. >> >> >> >>The two repeaters are maybe 1000' apart. >> >> >> >>I've only started having a problem with it since replacing my >> >>antenna so that I'm no longer stone deaf. >> >> >> >>I have a 5M wav file of the noise, if anyone's interested. >> >>It sounds like broadband noise at first, but then you notice >> >>the "feedback-ish" sound in it. At times we've heard what seems >> >>like bits of audio in the noise. >> >> >> >> 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/
