Re: [Repeater-Builder] New Repeater Desense Problems
Mike Morris WA6ILQ wrote: And some evening spend some time reading this: http://www.repeater-builder.com/db/db-about-rf-communications.pdf Yes, some of the info is 40 years old, but the physics of RF hasn't changed. Mike WA6ILQ And never will! At least not until somebody figures out how sub-space communications works! ;cD
RE: [Repeater-Builder] New Repeater Desense Problems
John, In the cases I have seen, an Iso-Tee is constructed by removing the center pin in the offset side of a UHF T connector, grinding it down until it is flat with the insulator surface (add a notch so you can re-insert with a screwdriver) and reinsert the pin into the connector. This provides for an indirect connection for testing purposes. The link below describes the theory/practice behind its design and use, although the author uses an insulator sleeve around the center pin of his connector rather than the design I am familiar with. http://www.conknet.com/~b_mobile/NoiseStuff.html This article describes the design I am familiar with: http://mrtmag.com/mag/radio_rf_samplers_directional/ If you have a Bird wattmeter, you can construct one for use with your meter: http://www.repeater-builder.com/projects/bird43sampler.html Hope this helps! Mark - N9WYS -Original Message- From: John Transue [EMAIL PROTECTED] Date: 2008/07/09 Wed AM 10:06:35 EDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems So, please, someone tell me, what is an iso tee/sampler slug? How is the equipmenthooked up for the desense test? John
Re: [Repeater-Builder] New Repeater Desense Problems
Additional accuracy can be obtained by providing a 50 ohm load for the generator. This can be accomplished by connecting the center of the ISO T to the center of the unmodified T to form an H configuration. Then connect the generator to one end of the unmodified T and a 50 ohm load to the other end of the unmodified T. This allows the generator to see a 50 ohm load. billb Yahoo! Groups Links **Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com! (www.tourtracker.com?NCID=aolmus0005000112)
Re: [Repeater-Builder] New Repeater Desense Problems
Replace the lmr400 with heliax .we hjave had nothing but problems with it since changing it to heliax the problem has been cleared up Thank You, Ian Wells, Kerinvale Comaudio, 361 Camboon Road.Biloela.4715 Phone 0749922574 or 0409159932 www.kerinvalecomaudio.com.au ---Original Message--- From: Bill Wilson Date: 8/07/2008 10:08:00 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill KJ4EX
Re: [Repeater-Builder] New Repeater Desense Problems
Bill, In finding desense first one must locate the problem. A given. I would start with putting GOOD dummy load on the duplexer output and do a desense test. This can be done with a local signal gen where you can vary the gen output and keying and unkey the transmitter. You should see no difference in the received signal with tx keyed or unkeyed. If you do then the desense is in the repeater. Next do the same test with the dummy load on the transmtter only. This will test for the desense being inside or outside the radio part of the repeater. I would look at your LMR400 and antenna. I think the LMR400 is a double shielded cable with different metals for the 2 shields. This is a no no in duplexed system. It generates noise. It has been discussed here on this board many many times and for good reason. If this is a problem replace with a good heliax. It is worth the cost. This is a start. 73, ron, n9ee/r From: Bill Wilson [EMAIL PROTECTED] Date: 2008/07/06 Sun PM 10:24:30 EDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill KJ4EX Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] New Repeater Desense Problems
Don't leave out the isolated TEE between the duplexer and dummy load, Ron. Hi, Steve NU5D Ron Wright wrote: Bill, In finding desense first one must locate the problem. A given. I would start with putting GOOD dummy load on the duplexer output and do a desense test. This can be done with a local signal gen where you can vary the gen output and keying and unkey the transmitter. You should see no difference in the received signal with tx keyed or unkeyed. If you do then the desense is in the repeater. Next do the same test with the dummy load on the transmtter only. This will test for the desense being inside or outside the radio part of the repeater. I would look at your LMR400 and antenna. I think the LMR400 is a double shielded cable with different metals for the 2 shields. This is a no no in duplexed system. It generates noise. It has been discussed here on this board many many times and for good reason. If this is a problem replace with a good heliax. It is worth the cost. This is a start. 73, ron, n9ee/r
Re: [Repeater-Builder] New Repeater Desense Problems
Have you run the repeater into a dummy load and check for desense? David = From: Bill Wilson [EMAIL PROTECTED] Date: 2008/07/07 Mon AM 02:24:30 WET To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill KJ4EX
RE: [Repeater-Builder] New Repeater Desense Problems
Not to hijack the thread, but a dummy load is NOT always a perfect test to eliminate the equipment. I think it’s a good start though. I just solved a situation where I had 15 db desense into a 600ft feedline / antenna and ZERO desense into a dummy load. This was using a sample slug ( same function as iso tee)in my bird 43 where the feed line attached to the cabinet. My assumption that the complete repeater, duplexers, isolator and cables were fine into a dummy load led me to look at the hardline and antenna and prepare for paying for a climb. Before we could properly test the feedline and antenna, the mastr II PA failed. (VHF) after replacing the amp, the 15 db desense problem was gone. So the failing amp liked the dummy load better than 600ft of 50ohm feedline and antenna . Or some product from the amp excited the feedline /antenna to create something on our input. The low level products on our input creating the desense were not visible when I had looked at the spectral output of the amp before it failed. Nothing like moving a mobile amp into a continuous duty heat sink, on you tailgate, on the 4th of July! 73 Don Kirchner W5DK From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, July 08, 2008 9:39 AM To: Bill Wilson; Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] New Repeater Desense Problems Have you run the repeater into a dummy load and check for desense? David = From: Bill Wilson [EMAIL PROTECTED] mailto:kj4ex%40yahoo.com Date: 2008/07/07 Mon AM 02:24:30 WET To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill – KJ4EX
Re: [Repeater-Builder] New Repeater Desense Problems
Just to echo previous comments, the LMR type cable (any cable with aluminum foil/braid combination) is suspect. This subject comes up here about every other week. Chuck WB2EDV - Original Message - From: Bill Wilson [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Sunday, July 06, 2008 10:24 PM Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill - KJ4EX Yahoo! Groups Links
Re: [Repeater-Builder] New Repeater Desense Problems
de W5DK wrote: Not to hijack the thread, but a dummy load is NOT always a perfect test to eliminate the equipment. I think it’s a good start though. I just solved a situation where I had 15 db desense into a 600ft feedline / antenna and ZERO desense into a dummy load. This was using a sample slug ( same function as iso tee)in my bird 43 where the feed line attached to the cabinet. My assumption that the complete repeater, duplexers, isolator and cables were fine into a dummy load led me to look at the hardline and antenna and prepare for paying for a climb. Before we could properly test the feedline and antenna, the mastr II PA failed. (VHF) after replacing the amp, the 15 db desense problem was gone. So the failing amp liked the dummy load better than 600ft of 50ohm feedline and antenna . Or some product from the amp excited the feedline /antenna to create something on our input. The low level products on our input creating the desense were not visible when I had looked at the spectral output of the amp before it failed. It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. There is lots of info on it on the repeater-builder web site. 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:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * 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/
Re: [Repeater-Builder] New Repeater Desense Problems
At 07:24 PM 07/06/08, you wrote: Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the very sensitive receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they discovered that the loops were 180 degrees out of phase, and when they turned them, the duplexers came right in. However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill KJ4EX Who told you to use the LMR coax for duplex use? Doesn't anybody read the archives of this group? There has been at least a dozen instances over the last few years where people have popped up and been told that LMR CABLE IS JUNK WHEN USED IN DUPLEX SERVICE. Go to this page: http://www.repeater-builder.com/antenna/ant-sys-index.html Read the 4 paragraphs under System Engineering and also the second and third articles there. This is also of interest: http://www.repeater-builder.com/antenna/andrew-shielding-effectiveness.pdf As to what cable you should use... it all depends on how well you want to hear. Increasing the talk range is easy - how much amplifier and duplexer can you afford? The average amateur radio repeater is limited by the fact that every user wants to use a 2w or 4w handheld instead of a 30w of 50w mobile. If you can't hear them you can't repeat them, so a repeater that has a 1.5db of feedline loss (100 feet of LMR400 at 2m) from the antenna to the receiver is not going to hear as well as one that has 0.5db of loss (100 feet of 7/8 inch heliax at 2m). People never seem to think about feedline loss on received signals... Look at the bottom third of this page: http://www.repeater-builder.com/antenna/wa2ise-coaxial-cable.html and look at the loss per 100 feet. Always favor your receiver. Once you have lost received signal (i.e. it's down into the noise level) all the preamps do is bring up the noise. This is also of interest: http://www.coasteltools.com/tech_cable_db_loss.htm And some evening spend some time reading this: http://www.repeater-builder.com/db/db-about-rf-communications.pdf Yes, some of the info is 40 years old, but the physics of RF hasn't changed. Mike WA6ILQ
Re: [Repeater-Builder] New Repeater Desense Problems
At 7/8/2008 11:37, you wrote: If you can't hear them you can't repeat them, so a repeater that has a 1.5db of feedline loss (100 feet of LMR400 at 2m) from the antenna to the receiver is not going to hear as well as one that has 0.5db of loss (100 feet of 7/8 inch heliax at 2m). ...except if your repeater is in SoCal, where the antenna noise temperature on 2 meters is about 10 dB above kTB, so throwing away a couple of dB between the antenna RX isn't going to hurt you. Bob NO6B
