[Repeater-Builder] Re: Rolling Pipe Sound
Yep, its still with me that nasty IM. Going to put a band pass filter in front of the receiver first as I do not have one at this time. Thanks for all the help. Just have to wait for parts for now. Scott KB7DZR --- In Repeater-Builder@yahoogroups.com, Nate Duehr n...@... wrote: Nasssty. Evil IM. Nice find. Nate WY0X On Dec 7, 2009, at 8:49 PM, larynl2 wrote: Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. I caught in one of your posts that your transmitter needs to be on for the problem to appear, so that's intermod causing your interference, not just a random carrier coming from a router or whatever device. The problem here was caused by an FM station on 89.9 about a mile away, and another one on 89.3 roughly six miles away, plus our transmitter on 147.06. A+B-C=D 147.06 + 89.9 - 89.3 = 147.66. The thing to watch for with FM broadcast intermod is the wide bandwidth of the intermod product. There was no interference until BOTH stations were quiet -- no modulation. Obviously, the instances of both being quiet simultaneously are quite random in length and occurrence, depending on the program material of each. I tracked the location of the mixing with the aid of a spectrum analyzer, which turned out to be safety cables threaded through the turnbuckles. Laryn K8TVZ
Re: [Repeater-Builder] Re: Rolling Pipe Sound
I recently located a very similar problem on a T-band public safety system, only in this case, it was two transmitters in a 28 channel 800 MHz trunker that were exactly 3 MHz apart that added that critical component to the mix. The end result was that every t-band repeater at that site would add it's own transmitter to the mix component, and would cause a feedback howl that could best be described as a rolling pipe. Adding to the confusion in finding it, it would hit the various t-band channels in what seemed like a random fashion. It wasn't until later that I realized what was happening is, the combination of activity on any particular T-band receiver would cause it's associated transmitter to activate (obviously!), and if the two 800 MHz transmitters in question were active at that time, the howling noise would start up. If the other repeaters were quiet, they would STAY quiet. Cross coding the PL's between your own transmitter and receiver can help mask the symptom, because your own transmitter may end up providing the PL (or DPL, as the case may be) needed to open the receiver. Depending on where the mix is actually taking place, you may or may not be able to locate it and actually fix it. In that case, masking it becomes the necessary solution. In my case, the mix is pervasive throughout the site - including miles of rusty chain link fence. Removing the Angle Linear preamp eliminated the symptom, but only because, since the mix product is a pretty low level, it's making the receivers sensitive enough to hear what's always there. Mel - WA6JBD --- On Mon, 12/7/09, larynl2 lar...@hotmail.com wrote: From: larynl2 lar...@hotmail.com Subject: [Repeater-Builder] Re: Rolling Pipe Sound To: Repeater-Builder@yahoogroups.com Date: Monday, December 7, 2009, 7:49 PM Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. I caught in one of your posts that your transmitter needs to be on for the problem to appear, so that's intermod causing your interference, not just a random carrier coming from a router or whatever device. The problem here was caused by an FM station on 89.9 about a mile away, and another one on 89.3 roughly six miles away, plus our transmitter on 147.06. A+B-C=D 147.06 + 89.9 - 89.3 = 147.66. The thing to watch for with FM broadcast intermod is the wide bandwidth of the intermod product. There was no interference until BOTH stations were quiet -- no modulation. Obviously, the instances of both being quiet simultaneously are quite random in length and occurrence, depending on the program material of each. I tracked the location of the mixing with the aid of a spectrum analyzer, which turned out to be safety cables threaded through the turnbuckles. Laryn K8TVZ Yahoo! Groups Links repeater-builder-fullfeatu...@yahoogroups.com
Re: [Repeater-Builder] Re: Rolling Pipe Sound
I have a wav (3Meg) file of the rolling pipe sound. What is the best way to get it to those that want to listen to it? 73, dave wa3gin - Original Message - From: Facility 406 DM09 To: Repeater-Builder@yahoogroups.com Sent: Monday, December 07, 2009 9:39 PM Subject: Re: [Repeater-Builder] Re: Rolling Pipe Sound I don't think I've ever heard a rolling pipe sound over a repeater, although, once I had some interesting feedback from an SSB transmitter with FM receiver. Is there a good clean recording available?
[Repeater-Builder] Re: Rolling Pipe Sound
Thanks for the quick reply The revers pair is a good point. I am in a remote area and did the full coordination but still we have had some odd ducting here as I am close to 9K mountains and I am at around 4K feet to start with. Tony I have not ran it without the tx pl. I have a few folks that like that including myself as I drop the tone before the TX, the controller is a ICS. But still for testing I may do that. I have echolink so I hook it up at night to the Ireland conference and set the system to listen only so I do not interfere with folks. Then with a program called echoproducer I can log each time the system gets kerchunched. sometimes its fine other times the log is big. Sorry I failed to put down its on 147.000 TX 147.600 RX. I have a repeater info page off of my weather station site. http://www.josephoregonweather.com/repeater.html --- In Repeater-Builder@yahoogroups.com, Tony KT9AC kt...@... wrote: Scott, You are not alone in this!! I too have been fighting a problem almost exactly like this - I've tried different PL tones on RX and TX and that seemed to keep it from self-oscillating. Seems to happen more when the weather is dry and I describe it as a growl sound. Happening on a MSF5000 at a commercial site. We too have numerous broadcast towers within 2 miles, and lots of Cellular/PCS antennas around. Mine is on UHF, yours appears to be high-band VHF (from the TKR-750 K2 note). I'm still working on a resolution, but again for now try either split tone or remove PL from the transmitter (CSQ). It would keep the repeater keyed up for several seconds, then drop signal and come back again (as long as the tail remained with PL output). I've also shortened the hang timer to 3 seconds to help. It wouldn't bring up the system unless someone kerchunked it, then it started. Tony, KT9AC
Re: [Repeater-Builder] Re: Rolling Pipe Sound
Scott, I also would second the reverse repeater theory. Years ago (many) we had a repeater in Western PA on 147.165 that would lock up with a Michigan repeater on 147.765 (both rightfully coordinated) and produce the pipe sound. In those days (1980s) everyone ran carrier squelch and we had some Lake Erie ducting once in a while. Its up to you, but was just a quick workaround that I started doing. Funny thing is I can get the growl when the system ran DPL and conditions are right...but its not the repeater since another temporary system I put in did the same thing. Sorry to hijack your note with my issue, but was hoping that there would be some commonality and we would both benefit. Thanks for the information on echoproducer, I might look into that. Tony offtracks1 wrote: Thanks for the quick reply The revers pair is a good point. I am in a remote area and did the full coordination but still we have had some odd ducting here as I am close to 9K mountains and I am at around 4K feet to start with. Tony I have not ran it without the tx pl. I have a few folks that like that including myself as I drop the tone before the TX, the controller is a ICS. But still for testing I may do that. I have echolink so I hook it up at night to the Ireland conference and set the system to listen only so I do not interfere with folks. Then with a program called echoproducer I can log each time the system gets kerchunched. sometimes its fine other times the log is big. Sorry I failed to put down its on 147.000 TX 147.600 RX. I have a repeater info page off of my weather station site. http://www.josephoregonweather.com/repeater.html http://www.josephoregonweather.com/repeater.html --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com, Tony KT9AC kt...@... wrote: Scott, You are not alone in this!! I too have been fighting a problem almost exactly like this - I've tried different PL tones on RX and TX and that seemed to keep it from self-oscillating. Seems to happen more when the weather is dry and I describe it as a growl sound. Happening on a MSF5000 at a commercial site. We too have numerous broadcast towers within 2 miles, and lots of Cellular/PCS antennas around. Mine is on UHF, yours appears to be high-band VHF (from the TKR-750 K2 note). I'm still working on a resolution, but again for now try either split tone or remove PL from the transmitter (CSQ). It would keep the repeater keyed up for several seconds, then drop signal and come back again (as long as the tail remained with PL output). I've also shortened the hang timer to 3 seconds to help. It wouldn't bring up the system unless someone kerchunked it, then it started. Tony, KT9AC Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: repeater-builder-dig...@yahoogroups.com repeater-builder-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: repeater-builder-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] Re: Rolling Pipe Sound
No worries, the more info the better. Echoproducer is the Bees Knees if you are running echolink. It is one very impressive and free program. Peter has put a lot of work into it. Scott --- In Repeater-Builder@yahoogroups.com, Tony KT9AC kt...@... wrote: Scott, I also would second the reverse repeater theory. Years ago (many) we had a repeater in Western PA on 147.165 that would lock up with a Michigan repeater on 147.765 (both rightfully coordinated) and produce the pipe sound. In those days (1980s) everyone ran carrier squelch and we had some Lake Erie ducting once in a while. Its up to you, but was just a quick workaround that I started doing. Funny thing is I can get the growl when the system ran DPL and conditions are right...but its not the repeater since another temporary system I put in did the same thing. Sorry to hijack your note with my issue, but was hoping that there would be some commonality and we would both benefit. Thanks for the information on echoproducer, I might look into that. Tony offtracks1 wrote: Thanks for the quick reply The revers pair is a good point. I am in a remote area and did the full coordination but still we have had some odd ducting here as I am close to 9K mountains and I am at around 4K feet to start with. Tony I have not ran it without the tx pl. I have a few folks that like that including myself as I drop the tone before the TX, the controller is a ICS. But still for testing I may do that. I have echolink so I hook it up at night to the Ireland conference and set the system to listen only so I do not interfere with folks. Then with a program called echoproducer I can log each time the system gets kerchunched. sometimes its fine other times the log is big. Sorry I failed to put down its on 147.000 TX 147.600 RX. I have a repeater info page off of my weather station site. http://www.josephoregonweather.com/repeater.html http://www.josephoregonweather.com/repeater.html --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com, Tony KT9AC kt9ac@ wrote: Scott, You are not alone in this!! I too have been fighting a problem almost exactly like this - I've tried different PL tones on RX and TX and that seemed to keep it from self-oscillating. Seems to happen more when the weather is dry and I describe it as a growl sound. Happening on a MSF5000 at a commercial site. We too have numerous broadcast towers within 2 miles, and lots of Cellular/PCS antennas around. Mine is on UHF, yours appears to be high-band VHF (from the TKR-750 K2 note). I'm still working on a resolution, but again for now try either split tone or remove PL from the transmitter (CSQ). It would keep the repeater keyed up for several seconds, then drop signal and come back again (as long as the tail remained with PL output). I've also shortened the hang timer to 3 seconds to help. It wouldn't bring up the system unless someone kerchunked it, then it started. Tony, KT9AC
[Repeater-Builder] Re: Rolling Pipe Sound
The router is right at 147.580 to almost 147.595. The repeater input is 147.600. So I plan to take that offline. All that cables are double shielded with no adapters ect. I do not have anything between the isolator and the duplexer. Where is a good dealer for a 5 or 8 band pass for the receiver? I may look at going with that for the first step as it is not very bad but a bugger that pops up now and then. Thanks for the help. Scott --- In Repeater-Builder@yahoogroups.com, Eric Lemmon wb6...@... wrote: Scott, A likely suspect is a carrier being emitted by a nearby computer or microprocessor. A few years ago, I was setting up a GR1225 repeater on a VHF channel, and I noticed that the receive indicator LED was lit steadily. My spectrum analyzer revealed that there was a low-level but steady carrier a few kHz off from my receive frequency. I then used my T-Hunt equipment to pinpoint my desktop computer as the source. In the course of my investigation, I also found weak but benign carriers being emitted from my TV set, my idle microwave oven, and my programmable thermostat. If it is an intermod problem, perhaps a DCI filter is far too wide to be of much help. I'd strongly suggest putting a 5 or 8 bandpass cavity ahead of the receiver- it is much sharper than the DCI product. Do you have a second harmonic notch filter, or a low-pass filter, following the isolator? Are all of the jumper cables double-shielded, with proper connectors on each end- that is, no adapters or barrels? 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of offtracks1 Sent: Monday, December 07, 2009 12:49 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Rolling Pipe Sound Thanks for all the post and for the web site and group. It's been very helpful to me as I have been setting up my system. My repeater system is a Kenwood TKR-750 K2, Telewave TPRD-1556 duplexer set (6 cavities), A Telewave Isolator on the PA. Running 1/2 Heilax to a Andrew DB224E antenna. This a repeater at my home as I am on a small hill. The antenna is about 40 feet vertical and 60 feet horizontally from the repeater/office. It works very well but I have had intermod issue that rears its head now and then that sounds like rolling pipe or hollow sound. I am runing a PL on both TX and RX. This sound opens up the receiver even. So my tx pl is getting back into the system. I have hunted down many noise makers in the office that could have been helping out. One was the Linksys router. I am going to replace it anyway as it makes a ton of noise I found. Changing my network from 100 to 10 on the card speed also reduced the noise levels. Still I get the rolling pipe sound now and then and it leaves as fast as it shows up. If I use my other antenna a Diamond F22 also fed with 1/2 Heliax I also get the same result. I do use a preamp but it also seems to not change with or without it. I have even ran it so the receive antenna is alone and the transmit is the other (split). I still get the rolling pipes now and then. I do have a FM radio station on 92.1 about 4 miles from me that is known to have a sloppy signal. Could it be that this is mixing with my system and creating this? Looking at getting a DCI Band pass filter on the receiver side but I am not sure if that is just throwing more money at this project and not getting anywhere still. Just wanted to see if anyone had some ideas? Scott KB7DZR
Re: [Repeater-Builder] Re: Rolling Pipe Sound
Just catchingup on this... yes the infamous rolling pipe sound. We had an issue with a link receiver that occassionaly would get hung-up in a loop, low audio but the correct PL. We switched from PL to DCT on the links and that solved the problem. We spent a year hunting for the source but no joy. Good Luck, dave WA3GIN W4AVA Trustee - Original Message - From: offtracks1 To: Repeater-Builder@yahoogroups.com Sent: Monday, December 07, 2009 5:25 PM Subject: [Repeater-Builder] Re: Rolling Pipe Sound No worries, the more info the better. Echoproducer is the Bees Knees if you are running echolink. It is one very impressive and free program. Peter has put a lot of work into it. Scott --- In Repeater-Builder@yahoogroups.com, Tony KT9AC kt...@... wrote:
Re: [Repeater-Builder] Re: Rolling Pipe Sound
Certain linksys routers may be able to take different the firmware. http://www.dd-wrt.com/site/index Of particular note is the ability to change the clock speed. Also it has been my experience that the router isn't really the source of the interference. Try switching the SMPS wall wart to one of the linear variety. On Mon, Dec 7, 2009 at 5:00 PM, WA3GIN wa3...@comcast.net wrote: Just catchingup on this... yes the infamous rolling pipe sound. We had an issue with a link receiver that occassionaly would get hung-up in a loop, low audio but the correct PL. We switched from PL to DCT on the links and that solved the problem. We spent a year hunting for the source but no joy. Good Luck, dave WA3GIN W4AVA Trustee - Original Message - *From:* offtracks1 worldroa...@fastmail.fm *To:* Repeater-Builder@yahoogroups.com *Sent:* Monday, December 07, 2009 5:25 PM *Subject:* [Repeater-Builder] Re: Rolling Pipe Sound No worries, the more info the better. Echoproducer is the Bees Knees if you are running echolink. It is one very impressive and free program. Peter has put a lot of work into it. Scott --- In Repeater-Builder@yahoogroups.com, Tony KT9AC kt...@... wrote:
RE: [Repeater-Builder] Re: Rolling Pipe Sound
Scott, One source is Telewave. Here are the datasheets for the 5 and 8 bandpass cavity filters: www.telewave.com/pdf/TWDS-5021.pdf www.telewave.com/pdf/TWDS-5031.pdf With the 30% Amateur discount, the 5 cavity will cost you about $231 plus shipping, and the 8 cavity is about $100 more. Other sources are Comprod, EMR, TX-RX, and Andrew. Some brands may require purchase through a distributor, such as Tessco, Hutton, or Talley. Always ask about a Ham discount when you are negotiating prices. Depending upon the size of your order, you may get 25% or 30%. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of offtracks1 Sent: Monday, December 07, 2009 3:56 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Rolling Pipe Sound The router is right at 147.580 to almost 147.595. The repeater input is 147.600. So I plan to take that offline. All that cables are double shielded with no adapters ect. I do not have anything between the isolator and the duplexer. Where is a good dealer for a 5 or 8 band pass for the receiver? I may look at going with that for the first step as it is not very bad but a bugger that pops up now and then. Thanks for the help. Scott --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , Eric Lemmon wb6...@... wrote: Scott, A likely suspect is a carrier being emitted by a nearby computer or microprocessor. A few years ago, I was setting up a GR1225 repeater on a VHF channel, and I noticed that the receive indicator LED was lit steadily. My spectrum analyzer revealed that there was a low-level but steady carrier a few kHz off from my receive frequency. I then used my T-Hunt equipment to pinpoint my desktop computer as the source. In the course of my investigation, I also found weak but benign carriers being emitted from my TV set, my idle microwave oven, and my programmable thermostat. If it is an intermod problem, perhaps a DCI filter is far too wide to be of much help. I'd strongly suggest putting a 5 or 8 bandpass cavity ahead of the receiver- it is much sharper than the DCI product. Do you have a second harmonic notch filter, or a low-pass filter, following the isolator? Are all of the jumper cables double-shielded, with proper connectors on each end- that is, no adapters or barrels? 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of offtracks1 Sent: Monday, December 07, 2009 12:49 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Rolling Pipe Sound Thanks for all the post and for the web site and group. It's been very helpful to me as I have been setting up my system. My repeater system is a Kenwood TKR-750 K2, Telewave TPRD-1556 duplexer set (6 cavities), A Telewave Isolator on the PA. Running 1/2 Heilax to a Andrew DB224E antenna. This a repeater at my home as I am on a small hill. The antenna is about 40 feet vertical and 60 feet horizontally from the repeater/office. It works very well but I have had intermod issue that rears its head now and then that sounds like rolling pipe or hollow sound. I am runing a PL on both TX and RX. This sound opens up the receiver even. So my tx pl is getting back into the system. I have hunted down many noise makers in the office that could have been helping out. One was the Linksys router. I am going to replace it anyway as it makes a ton of noise I found. Changing my network from 100 to 10 on the card speed also reduced the noise levels. Still I get the rolling pipe sound now and then and it leaves as fast as it shows up. If I use my other antenna a Diamond F22 also fed with 1/2 Heliax I also get the same result. I do use a preamp but it also seems to not change with or without it. I have even ran it so the receive antenna is alone and the transmit is the other (split). I still get the rolling pipes now and then. I do have a FM radio station on 92.1 about 4 miles from me that is known to have a sloppy signal. Could it be that this is mixing with my system and creating this? Looking at getting a DCI Band pass filter on the receiver side but I am not sure if that is just throwing more money at this project and not getting anywhere still. Just wanted to see if anyone had some ideas? Scott KB7DZR
[Repeater-Builder] Re: Rolling Pipe Sound
Eric Thanks, I have had great service from Telwave. They were very helpful for newbie. Thanks for all the tips and ideas everyone. It took me on a yet one more of many sniffing runs with my ht and about 10 feet of coax with about 2 of the center exposed so I could really sniff close. Well I really think (HOPE) I found it maybe. Right spot on the input I can get a sound that kind of fits the sound I have been getting. I have my full weather station here as many folks use it including the weather service. It updated on the web ect. Well its a wired Davis weather station, so all the wires going to all the sensors work well as a antenna. After some close hunting it will fully open the Ht's squelch right on the input. it is coming from the one line I did not have a bead on. Its the main data line to the computer system that then records and sends it out to my web page. Now with a snap on bead on it I only get it to open up right at the side of the snap on bead that is running into the weather station. So I put one on each end and that really weakend the signal. It still present but you have be right on it. This just may be it as I have shut down everything but the weather station and it was unplugged from the power but it has a 9 volt backup battery in it. We will see, I have claimed victory too early before with this noise. So the next test is wait and see. By the way the DB224E Antenna is one very nice system its really woke up this repeater. I got it installed just about 2 weeks ago and switched off the backup antenna the diamond F22, its a good antenna but not for full time repeater service compared to the DB224E Scott KB7DZR --- In Repeater-Builder@yahoogroups.com, Eric Lemmon wb6...@... wrote: Scott, One source is Telewave. Here are the datasheets for the 5 and 8 bandpass cavity filters: www.telewave.com/pdf/TWDS-5021.pdf www.telewave.com/pdf/TWDS-5031.pdf With the 30% Amateur discount, the 5 cavity will cost you about $231 plus shipping, and the 8 cavity is about $100 more. Other sources are Comprod, EMR, TX-RX, and Andrew. Some brands may require purchase through a distributor, such as Tessco, Hutton, or Talley. Always ask about a Ham discount when you are negotiating prices. Depending upon the size of your order, you may get 25% or 30%. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of offtracks1 Sent: Monday, December 07, 2009 3:56 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Rolling Pipe Sound The router is right at 147.580 to almost 147.595. The repeater input is 147.600. So I plan to take that offline. All that cables are double shielded with no adapters ect. I do not have anything between the isolator and the duplexer. Where is a good dealer for a 5 or 8 band pass for the receiver? I may look at going with that for the first step as it is not very bad but a bugger that pops up now and then. Thanks for the help. Scott --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , Eric Lemmon wb6fly@ wrote: Scott, A likely suspect is a carrier being emitted by a nearby computer or microprocessor. A few years ago, I was setting up a GR1225 repeater on a VHF channel, and I noticed that the receive indicator LED was lit steadily. My spectrum analyzer revealed that there was a low-level but steady carrier a few kHz off from my receive frequency. I then used my T-Hunt equipment to pinpoint my desktop computer as the source. In the course of my investigation, I also found weak but benign carriers being emitted from my TV set, my idle microwave oven, and my programmable thermostat. If it is an intermod problem, perhaps a DCI filter is far too wide to be of much help. I'd strongly suggest putting a 5 or 8 bandpass cavity ahead of the receiver- it is much sharper than the DCI product. Do you have a second harmonic notch filter, or a low-pass filter, following the isolator? Are all of the jumper cables double-shielded, with proper connectors on each end- that is, no adapters or barrels? 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of offtracks1 Sent: Monday, December 07, 2009 12:49 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Rolling Pipe Sound Thanks for all the post and for the web site and group. It's been very helpful to me as I have been setting up my system. My repeater system is a Kenwood TKR-750 K2, Telewave TPRD-1556 duplexer set (6 cavities), A Telewave Isolator on the PA. Running 1/2 Heilax to a Andrew DB224E antenna
Re: [Repeater-Builder] Re: Rolling Pipe Sound
I don't think I've ever heard a rolling pipe sound over a repeater, although, once I had some interesting feedback from an SSB transmitter with FM receiver. Is there a good clean recording available? Kurt
[Repeater-Builder] Re: Rolling Pipe Sound
Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. I caught in one of your posts that your transmitter needs to be on for the problem to appear, so that's intermod causing your interference, not just a random carrier coming from a router or whatever device. The problem here was caused by an FM station on 89.9 about a mile away, and another one on 89.3 roughly six miles away, plus our transmitter on 147.06. A+B-C=D 147.06 + 89.9 - 89.3 = 147.66. The thing to watch for with FM broadcast intermod is the wide bandwidth of the intermod product. There was no interference until BOTH stations were quiet -- no modulation. Obviously, the instances of both being quiet simultaneously are quite random in length and occurrence, depending on the program material of each. I tracked the location of the mixing with the aid of a spectrum analyzer, which turned out to be safety cables threaded through the turnbuckles. Laryn K8TVZ
Re: [Repeater-Builder] Re: Rolling Pipe Sound
larynl2 wrote: Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. Or AM. Or an AM station ON 600 kc also.
Re: [Repeater-Builder] Re: Rolling Pipe Sound
Nasssty. Evil IM. Nice find. Nate WY0X On Dec 7, 2009, at 8:49 PM, larynl2 wrote: Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. I caught in one of your posts that your transmitter needs to be on for the problem to appear, so that's intermod causing your interference, not just a random carrier coming from a router or whatever device. The problem here was caused by an FM station on 89.9 about a mile away, and another one on 89.3 roughly six miles away, plus our transmitter on 147.06. A+B-C=D 147.06 + 89.9 - 89.3 = 147.66. The thing to watch for with FM broadcast intermod is the wide bandwidth of the intermod product. There was no interference until BOTH stations were quiet -- no modulation. Obviously, the instances of both being quiet simultaneously are quite random in length and occurrence, depending on the program material of each. I tracked the location of the mixing with the aid of a spectrum analyzer, which turned out to be safety cables threaded through the turnbuckles. Laryn K8TVZ
