Re: [Repeater-Builder] The duplexer story...
Tim, a couple of questions come to mind. 1.) Are you trying to tune a T-band Duplexer down to 440? Not reccomended. 2.) Are you running a circulator between the duplexer and the antenna? 3.) Are you using the same cables out of the repeater to connect to the duplexer (either one) and seeing a change? Barry --- Tim S. [EMAIL PROTECTED] wrote: As I stated a few times here I have a duplexer that has been giving me desense. To get rid of the desense I turned down the TX power until it went away because the duplexer is rusty and hasn't been messed with in 20+ years. I came across another duplexer in a base station cabinet we had and pulled the duplexer out. Here are the specs of it: TPRD-14744 (470-512 MHz) Type: 4 cavity pass-reject Minimum freq. spacing 3 MHz Insertion loss 1.0 dB Max. continuous power 250 watts TX noise supp. at Rx freq. 90 dB Rx isolation at TX freq. 90 dB Temperature range -30 to +70C I used the tracking generator and tuned and notched it on frequency. My plan was to use this duplexer as a backup if the original one would not tune. When I checked desense on the original again it was around 10db. I pulled the duplexer and found the reject was only about -75db on both sides. I adjusted the notches and got it down under -90db but noticed it jumped around -95db then -90db, etc... I did use double shielded cables for tuning. I checked the passes and they seemed ok, so I did not touch them. Put it back in place and turned the power back up from 15 watts out of the PA to 42 watts out of the PA. The desense jumped big time to around 20db. So I pulled the old duplexer and put in the spare. Now I have no measurable desense. So that's a plus. However, I put the service monitor on the PA output and read 42 watts. Hooked the cabling up to the duplexer and then checked the output of the duplexer and only read 22 watts. That's like a -2.8db loss. I didn't think at the time to check the interconnect cable from the PA to the duplexer, but I can't imagine that having a -1.8db loss. Since the duplexer should only have -1.0 db insertion loss. When I tuned the replacement I double checked all the peaks locked them down then did the rejects. So I am pretty confident the duplexer is set right. So, in the end the repeater went from 15 watts out of the duplexer with 10db desense to 22 watts out with no desense. 1. Can something in the original duplexer go bad internally to cause the desense? Or must my tuning be suspect? 2. Think I need to worry about the -2.8 db power loss? All I can think of doing is checking the interconnect cable from the PA to the duplexer input. Another note: When I retuned the base station duplexer, I kept the low side low and the high side high, meaning I am now transmitting on what was originally the RX port since it went from a base station use to repeater. Could this be a problem if I really have -2.8db insertion loss? -Tim Yahoo! Groups Links [EMAIL PROTECTED] ___ Do you Yahoo!? Declare Yourself - Register online to vote today! http://vote.yahoo.com 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/
Re: [Repeater-Builder] The duplexer story...
On Thursday 30 September 2004 02:16 am, Tim S. wrote: However, I put the service monitor on the PA output and read 42 watts. Hooked the cabling up to the duplexer and then checked the output of the duplexer and only read 22 watts. That's like a -2.8db loss. What is the SWR looking into the duplexer? Have you tried different length cables from the transmitter to the duplexer and looked to see if the power coming out of the duplexer changes? When hooked to the duplexer, your PA may not be putting out 42 watts. I keep a selection of various length cables (in increments of 1/8 wavelength) at the repeater site for investigating stuff like this. When I tuned the replacement I double checked all the peaks locked them down then did the rejects. So I am pretty confident the duplexer is set right. Even a properly tuned duplexer can upset a PA. 1. Can something in the original duplexer go bad internally to cause the desense? Or must my tuning be suspect? Any number of things could go wrong with a duplexer... bad cavity interconnect cables, internal corrosion, hidden lightning damage... 2. Think I need to worry about the -2.8 db power loss? I would investigate to find out why you're seeing these numbers. If you're really losing 2.8 dB in the duplexer, something isn't right. Try some different cable lengths between transmitter and duplexer to see if it has an effect. Note: placing a directional coupler between the transmitter and duplexer to measure power there may or may not work like you want... you should simultaneously measure power out of the duplexer, since adding a coupler after the PA changes the line length and hence may significantly change the load the PA sees! Made that mistake once or twice Let us know what you find. Paul 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/
Re: [Repeater-Builder] The duplexer story...
Say Tim; If you have all of that rust it seems like besides high resistance for proper contact wouldn't it cause some sort of leakage for that desense problem, as well radiate some percentage of interference ? even though you turned the power down, I was wondering how much work it would be to replace that connector, I am guessing it was riveted in during production. MH - Original Message - From: Tim S. [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, September 30, 2004 2:16 AM Subject: [Repeater-Builder] The duplexer story... As I stated a few times here I have a duplexer that has been giving me desense. To get rid of the desense I turned down the TX power until it went away because the duplexer is rusty and hasn't been messed with in 20+ years. I came across another duplexer in a base station cabinet we had and pulled the duplexer out. Here are the specs of it: TPRD-14744 (470-512 MHz) Type: 4 cavity pass-reject Minimum freq. spacing 3 MHz Insertion loss 1.0 dB Max. continuous power 250 watts TX noise supp. at Rx freq. 90 dB Rx isolation at TX freq. 90 dB Temperature range -30 to +70C I used the tracking generator and tuned and notched it on frequency. My plan was to use this duplexer as a backup if the original one would not tune. When I checked desense on the original again it was around 10db. I pulled the duplexer and found the reject was only about -75db on both sides. I adjusted the notches and got it down under -90db but noticed it jumped around -95db then -90db, etc... I did use double shielded cables for tuning. I checked the passes and they seemed ok, so I did not touch them. Put it back in place and turned the power back up from 15 watts out of the PA to 42 watts out of the PA. The desense jumped big time to around 20db. So I pulled the old duplexer and put in the spare. Now I have no measurable desense. So that's a plus. However, I put the service monitor on the PA output and read 42 watts. Hooked the cabling up to the duplexer and then checked the output of the duplexer and only read 22 watts. That's like a -2.8db loss. I didn't think at the time to check the interconnect cable from the PA to the duplexer, but I can't imagine that having a -1.8db loss. Since the duplexer should only have -1.0 db insertion loss. When I tuned the replacement I double checked all the peaks locked them down then did the rejects. So I am pretty confident the duplexer is set right. So, in the end the repeater went from 15 watts out of the duplexer with 10db desense to 22 watts out with no desense. 1. Can something in the original duplexer go bad internally to cause the desense? Or must my tuning be suspect? 2. Think I need to worry about the -2.8 db power loss? All I can think of doing is checking the interconnect cable from the PA to the duplexer input. Another note: When I retuned the base station duplexer, I kept the low side low and the high side high, meaning I am now transmitting on what was originally the RX port since it went from a base station use to repeater. Could this be a problem if I really have -2.8db insertion loss? -Tim Yahoo! Groups Links 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/
Re: [Repeater-Builder] The duplexer story...
At 12:09 AM 9/30/2004 -0700, you wrote: Tim, a couple of questions come to mind. 2.) Are you running a circulator between the duplexer and the antenna? --??? Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We now offer complete Kenwood TKR repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net 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/
RE: [Repeater-Builder] The duplexer story...
Comments within... -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Tim, a couple of questions come to mind. 1.) Are you trying to tune a T-band Duplexer down to 440? Not reccomended. No I am not trying to make it go to ham band. I maintain a private tband repeater. 2.) Are you running a circulator between the duplexer and the antenna? It would between the TX and the duplexer, but I know what you meant. And I am not running one. 3.) Are you using the same cables out of the repeater to connect to the duplexer (either one) and seeing a change? Not sure what you mean here. I took my test cable from the output of the transmitter and measured 42 watts. Then I hooked the cable from the transmitter to the duplexer input. Next I took my measurement from the duplexer antenna port. So, if your asking did I take a measurement through the cable from the pa to the duplexer no. I should have. Thanks for the input Barry. -Tim 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/
RE: [Repeater-Builder] The duplexer story...
-Original Message- From: Paul Kelley [mailto:[EMAIL PROTECTED] What is the SWR looking into the duplexer? Did not check that. What should it be? I assume 10% or less reflected. Have you tried different length cables from the transmitter to the duplexer and looked to see if the power coming out of the duplexer changes? Nope, but that's next on my list. I would investigate to find out why you're seeing these numbers. If you're really losing 2.8 dB in the duplexer, something isn't right. Try some different cable lengths between transmitter and duplexer to see if it has an effect. I plan on checking out some more. I am going to put a barrel connector on the end of the PA coax and measure just before it goes into the duplexer then measure the output of the duplexer. If that still seems funky I will try a different length cable. But... what if the duplexer does have the -2.8 loss, then I guess retuning is in order? I read on the repeater builder site that some people tune with the TX power at the site. That seems a bit risky to me and it would drastically change the notches. Let us know what you find. Will do! Thanks Paul. -Tim 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/
Re: [Repeater-Builder] The duplexer story...
Tim S. wrote: -Original Message- From: Paul Kelley [mailto:[EMAIL PROTECTED] What is the SWR looking into the duplexer? Did not check that. What should it be? I assume 10% or less reflected. 4% is 1.5:1 (100W out - 4W back OR 50W out - 2W back) It should be no more at the TX end of the duplexer than at the antenna end of the duplexer. If it is higher, look for a spurious TX. That might also explain your original desense as well as the additional power out. Joe M. 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/
RE: [Repeater-Builder] The duplexer story...
Thanks Joe. I'll check that out. -Tim -Original Message- From: mch [mailto:[EMAIL PROTECTED] Sent: Thursday, September 30, 2004 10:44 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] The duplexer story... Tim S. wrote: -Original Message- From: Paul Kelley [mailto:[EMAIL PROTECTED] What is the SWR looking into the duplexer? Did not check that. What should it be? I assume 10% or less reflected. 4% is 1.5:1 (100W out - 4W back OR 50W out - 2W back) It should be no more at the TX end of the duplexer than at the antenna end of the duplexer. If it is higher, look for a spurious TX. That might also explain your original desense as well as the additional power out. Joe M. 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/
Re: [Repeater-Builder] The duplexer story...
What is the SWR looking into the duplexer? Did not check that. What should it be? I assume 10% or less reflected. Ideally it should be not much higher than the antenna SWR, but even if SWR into the duplexer is low, duplexers can look reactive and cause some PAs to act up. And even a *slightly* mistuned duplxer can look really ugly. But... what if the duplexer does have the -2.8 loss, then I guess retuning is in order? If the duplexer really has 2.8 dB loss, I would try retuning it. It shouldn't be that high. I read on the repeater builder site that some people tune with the TX power at the site. That seems a bit risky to me and it would drastically change the notches. That's a controversial subject. I don't feel comfortable tuning under power, but some do. I could never convince myself there wouldn't be damaging arcing at the finger stock. Paul 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/
