Re: [Repeater-Builder] Help with intermod between repeaters.
wa5luy wrote: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Had the same exact situation with 146.745 and 147.345 years ago. Both MICOR's, not that it matters. It can happen with any repeater spacing that is 600 kiloHertz from one another, and the resulting mix lands on the repeater input. You'll need to install a circulator or isolator on the repeater that is causing the mix. If both repeaters are mixing, then both will need a circulator. This has nothing to do with whether or not the MICOR's were originally built for repeater duty or not. It's a mix that is happening in the repeater PA's. Kevin Custer
Re: [Repeater-Builder] Help with intermod between repeaters.
You need to reject the opposite TX on each repeater. Your BP filters were set wrong. You rejected the RX on the TX side - something the duplexer should be doing already. You need to install them in the repeater and reject the other TX. IOW, install a filter in the .16 repeater and notch the .36 TX. A good duplexer should do this as well, but many don't. Joe M. On Sat 14/02/09 6:34 PM , wa5luy wa5...@cablelynx.com sent: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a ¼ KW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of ½ hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50DB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of.76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the ¼ KW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavity's I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 DB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70DB of rejection and 2DB in the pass. I recorded the amount of signal needed to cause the mixing. I then put the cavities between the signal generator and transmitter. To my surprise the amount of signal to start mixing was about the same. The cavities are the type with a T on one port and a compression capacitor for the reject tuning. Some questions I have for the group are: 1. What is the best type of cavity filter to use in this situation and where should it be placed? 2. Has anyone else seen that, been there, done that, and what was your solution? Any information or ideas will be appreciated. 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/
RE: [Repeater-Builder] Help with intermod between repeaters.
The first question that enters my mind is, were both Micor stations originally built as repeaters, with the extra filters and shielding plates, or are one or both base stations that have been converted to repeaters? It is important that the extra shield plates provided with repeater stations are securely in place, with all screws installed. The second question is, are either or both repeaters equipped with ferrite isolators? Thank you for performing some outstanding troubleshooting, and for providing detailed information about your findings! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of wa5luy Sent: Saturday, February 14, 2009 3:35 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Help with intermod between repeaters. Bear with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a ¼ kW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of ½ hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50dB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of .76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the ¼ kW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavities, I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 dB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70 dB of rejection and 2 dB in the pass. I recorded the amount of signal needed to cause the mixing. I then put the cavities between the signal generator and transmitter. To my surprise the amount of signal to start mixing was about the same. The cavities are the type with a T on one port and a compression capacitor for the reject tuning. Some questions I have for the group are: 1. What is the best type of cavity filter to use in this situation and where should it be placed? 2. Has anyone else seen that, been there, done that, and what was your solution? Any information or ideas will be appreciated.
Re: [Repeater-Builder] Help with intermod between repeaters.
I hate to tell you, a definite way to eliminate the problem, is a frequency change so that the output of the two transmitters are no longer not 600 khz apart. It is possible that the mixing is occurring in one of the PA's. If the problem is a mix in the TX, an isolator on the offending TX should solve it. I like the Sinclair isolators. 2A-B Most likely a 3rd order intermod product 146.76 X 2 = 293.52 293.52 - 147.36 = 146.16 Bad place for it to end up on. I have run into this problem several times. Telco : I think you meant to say, the trouble must be on your end, it is leaving here ok... I can't use that excuse, my SXS office does not talk to the outside world yet... Good Luck John At 06:34 PM 2/14/2009, you wrote: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a ¼ KW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of ½ hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50DB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of.76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the ¼ KW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavity's I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 DB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70DB of rejection and 2DB in the pass. I recorded the amount of signal needed to cause the mixing. I then put the cavities between the signal generator and transmitter. To my surprise the amount of signal to start mixing was about the same. The cavities are the type with a T on one port and a compression capacitor for the reject tuning. Some questions I have for the group are: 1. What is the best type of cavity filter to use in this situation and where should it be placed? 2. Has anyone else seen that, been there, done that, and what was your solution? Any information or ideas will be appreciated. Yahoo! Groups Links
RE: [Repeater-Builder] Help with intermod between repeaters.
We had same problem with 146.940/340 and 146.640/040 few years ago, ( distance between repeaters same as yours); tried as many situations as you mentioned, we ended in using in our repeater 146.940 two separated antennas, one for RX and other for TX and the duplexer, a WP-629 used just as filters, this solved the problem 100%. Juan Tellez, XE2SI From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of John Sichert Sent: Saturday, February 14, 2009 5:13 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Help with intermod between repeaters. I hate to tell you, a definite way to eliminate the problem, is a frequency change so that the output of the two transmitters are no longer not 600 khz apart. It is possible that the mixing is occurring in one of the PA's. If the problem is a mix in the TX, an isolator on the offending TX should solve it. I like the Sinclair isolators. 2A-B Most likely a 3rd order intermod product 146.76 X 2 = 293.52 293.52 - 147.36 = 146.16 Bad place for it to end up on. I have run into this problem several times. Telco : I think you meant to say, the trouble must be on your end, it is leaving here ok... I can't use that excuse, my SXS office does not talk to the outside world yet... Good Luck John At 06:34 PM 2/14/2009, you wrote: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a ¼ KW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of ½ hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50DB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of.76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the ¼ KW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavity's I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 DB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70DB of rejection and 2DB in the pass. I recorded the amount of signal needed to cause the mixing. I then put the cavities between the signal generator and transmitter. To my surprise the amount of signal to start mixing was about the same. The cavities are the type with a T on one port and a compression capacitor for the reject tuning. Some questions I have for the group are: 1. What is the best type of cavity filter to use in this situation and where should it be placed? 2. Has anyone else seen that, been there, done that, and what was your solution? Any information or ideas will be appreciated. Yahoo! Groups Links __ Información de ESET Smart Security, versión de la base de firmas de virus 3846 (20090211) __ ESET Smart Security ha comprobado este mensaje. http://www.eset.com
Re: [Repeater-Builder] Help with intermod between repeaters.
There used to be a couple of high power paging transmitters in town 600 KHz apart in the 152 MHz range that used to raise hell with several ham repeaters, glad they are gone now. tom [Original Message] From: John Snitcher jo...@sxsco.com To: Repeater-Builder@yahoogroups.com Date: 2/14/2009 8:05:38 PM Subject: Re: [Repeater-Builder] Help with intermod between repeaters. I hate to tell you, a definite way to eliminate the problem, is a frequency change so that the output of the two transmitters are no longer not 600 khz apart. It is possible that the mixing is occurring in one of the PA's. If the problem is a mix in the TX, an isolator on the offending TX should solve it. I like the Sinclair isolators. 2A-B Most likely a 3rd order intermod product 146.76 X 2 = 293.52 293.52 - 147.36 = 146.16 Bad place for it to end up on. I have run into this problem several times. Telco : I think you meant to say, the trouble must be on your end, it is leaving here ok... I can't use that excuse, my SXS office does not talk to the outside world yet... Good Luck John At 06:34 PM 2/14/2009, you wrote: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a ¼ KW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of ½ hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50DB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of.76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the ¼ KW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavity's I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 DB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70DB of rejection and 2DB in the pass. I recorded the amount of signal needed to cause the mixing. I then put the cavities between the signal generator and transmitter. To my surprise the amount of signal to start mixing was about the same. The cavities are the type with a T on one port and a compression capacitor for the reject tuning. Some questions I have for the group are: 1. What is the best type of cavity filter to use in this situation and where should it be placed? 2. Has anyone else seen that, been there, done that, and what was your solution? Any information or ideas will be appreciated. Yahoo! Groups Links Yahoo! Groups Links 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: mailto:repeater-builder-dig...@yahoogroups.com mailto:repeater-builder-fullfeatu
Re: [Repeater-Builder] Help with intermod between repeaters.
We have a similar problem in the Twin Cities in Minnesota where we have two AM broadcasting stations that are 600 Khz apart. One is a 50,000 watt station on 1500 Khz and the other is a 10,000 watt station on 900 Khz. They are located about 5 miles apart. qs both stations are on-the-air 24 hours per day the 600 Khz signal is constantly on. Ever tried to build a filter for 1500 or 900 Khz to notch them out ? We have found (and located) this 600 Khz carrier on the high voltage power lines (500,000 V) that run close (within 1/2 mile) to the 50,000 watt station. You can hear the 600 Khz signal (with audio from both stations) from the stations on a AM car radio within 10 miles all along the power lines.. We have had to go to split site 2 meter repeaters within 15 mile radius of the two stations. Paul K0LAV - Original Message - From: Thomas Oliver tsoli...@tir.com To: Repeater-Builder@yahoogroups.com Sent: Saturday, February 14, 2009 7:34:55 PM GMT -06:00 US/Canada Central Subject: Re: [Repeater-Builder] Help with intermod between repeaters. There used to be a couple of high power paging transmitters in town 600 KHz apart in the 152 MHz range that used to raise hell with several ham repeaters, glad they are gone now. tom [Original Message] From: John Snitcher jo...@sxsco.com To: Repeater-Builder@yahoogroups.com Date: 2/14/2009 8:05:38 PM Subject: Re: [Repeater-Builder] Help with intermod between repeaters. I hate to tell you, a definite way to eliminate the problem, is a frequency change so that the output of the two transmitters are no longer not 600 khz apart. It is possible that the mixing is occurring in one of the PA's. If the problem is a mix in the TX, an isolator on the offending TX should solve it. I like the Sinclair isolators. 2A-B Most likely a 3rd order intermod product 146.76 X 2 = 293.52 293.52 - 147.36 = 146.16 Bad place for it to end up on. I have run into this problem several times. Telco : I think you meant to say, the trouble must be on your end, it is leaving here ok... I can't use that excuse, my SXS office does not talk to the outside world yet... Good Luck John At 06:34 PM 2/14/2009, you wrote: Bare with me this is a bit long. Our repeater is on 146.76TX / 146.16RX. In the next town the repeater having the problem is on 147.36TX / 147.96RX. Both repeaters are Motorola Micors. Our repeater is a 100 watt PA running about 60watts with a single band pass cavity between TX and a 4 cavity BPBR duplexer connected to 250 feet of 7/8 hard line and a DB224 antenna. The distance between repeaters is about 18 miles line of sight with no obstructions. The other repeater is running a smaller PA driver with an output of 25 watts. I am not sure of the full power capability of this driver. This PA then drives a � KW tube type final set at about 90 watts. This is connected to a 4 cavity BPBR duplexer, 200 feet of � hard line, and a DB224 antenna. The problem is when the our repeater 146.76 is in transmit and someone keys the 147.36 repeater a loop condition is set up locking on the 147.36 on until the 146.76 drops. Also audio feedback is heard on the 146.36 repeater. This is typical receiver transmitter intermod. Here is what I have done so for. I checked the 146.76 repeater and there is no signal on it on 147.96 or any other frequency other than 146.76. I then drove to the 146.36 repeater location and from my car in front of the repeater building duplicated the problem by transmitting on 146.76. As we used to say in the phone business, the trouble is leaving here OK. Next I put a calibrated receiver on the TX port of their BPBR duplexer and measured about -50DB when the 146.76 repeater was on. Also I could not squelch out the .76 signal by holding my hands over the antenna of my handheld radio in the building. There is lots of.76 signal down there so I suspect transmitter mixing of the 146.76 with 147.36 in the .36 PA. But where? I disconnected the � KW PA and hooked the driver up directly to the duplexer and the mixing signal on 147.96 is worse. I then put one band pass 147.36, band reject 147. 76 cavity between the PA driver and the duplexer. To my surprise the mixing signal on 147.96 is even higher! I also tried a single band pass cavity with about the same results. Having run out of cavity's I came back home. I realize their PA driver most likely needs to be checked. If the driver PA is ok they will need 30 to 50 DB of isolation between the 147.36 final and the duplexer which will be at least two cavities. I was able to duplicate this mixing with a couple of 2 meter radios, a lossy T connector and a signal generator. I took two high pass cavities out of a duplexer tuning then to pass 147.36 and reject 146.76. I ended up with around 70DB of rejection and 2DB in the pass. I
