[Repeater-Builder] Re: Use a band pass filter between pass-reject duplexer and antenna?
Eric Lemmon WB6FLY gave the best response to my question of how common is it to place a bandpass fillter betweeen antenna and duplexer. Most assumed a ham repeater with tx circulator and high rejection pass/reject duplexer which is correct. As I read the resposes it seems the answer is: this is not very common at all and not the best way to lower a nose floor to increase Rx sensitivy. It also adds to Tx power loss by a few dB. If broad enough to pass both Tx and Rx then the skirts are too broad to be helpful in eliminating RF from near by out of ham band high power transmitters. The repeater owner said he allowed a radio shop to install it that way, but it did NOT do the job of lowering the noise floor as promised. I questioned the wisdom, but thought I would ask if others had do it that way and why. --- In Repeater-Builder@yahoogroups.com, Eric Lemmon [EMAIL PROTECTED] wrote: I'm responding to you directly, as well as to the list, because your question is a very good one that should be answered publicly. Without much fear of contradiction, I will state that a bandpass/bandreject duplexer has precious little bandpass effect. Sure, when you look at a response plot that covers 10 MHz, it may look very selective, but in reality the bandpass action is rather subtle. A whole lot of RF can blow through a Bp/Br duplexer in either direction, but MOST of the time this deficiency doesn't cause a problem. I would not put a BP cavity between the duplexer and the antenna, simply because such a cavity would diminish the function of the duplexer. Now, if you want to put a preamp between the duplexer and the receiver, a BP cavity tuned to the receive frequency is a very good idea. This BP filter should follow the duplexer and precede the preamp. Two 8 cavities with 1.0 dB IL work well. If you have a solid-state PA that has significant sideband noise, you might consider placing a BP filter between the PA and the duplexer. If you are using a ferrite isolator to protect the PA, a BP cavity filter between the isolator and the duplexer can take the place of a 2nd- harmonic notch filter or low-pass filter. At a crowded commercial site, you may be required to have a BP cavity on the TX side. 73, Eric Lemmon WB6FLY w7aor wrote: How common is it to use a band pass filter ahead of a pass-reject duplexer, i.e., between the duplexer and feed line to antenna. Any reason for adding a band pass filter there on antenna input to duplexer vs. between the preamp pre selector cavities receiver port of duplexer. Please respond to w7aor @narri.org 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] Re: Use a band pass filter between pass-reject duplexer and antenna?
--- w7aor [EMAIL PROTECTED] wrote: Eric Lemmon WB6FLY gave the best response to my question of how common is it to place a bandpass fillter betweeen antenna and duplexer. Most assumed a ham repeater with tx circulator and high rejection pass/reject duplexer which is correct. About 25 years ago I had Wacom retrofit a 4 cavity bp/br 2 meter duplexer with two pass cavities. One for the receive side to provide out of band rejection and one on the transmitt side to make it ballanced looking if for nothing else. The repeater was in an area with lots of other transmitters near it. Must have been over 100 antennas in a 3 block area. Later I noticed they were offering that design in their catalog. Seems most bp/br duplexers do not really have taht much rejection of out of band signals. Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs 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] Re: Use a band pass filter between pass-reject duplexer and antenna?
Hi all, This topic is very well described in an article (on Kevin's website) by Jacques Audet VE2AZX. It is a large file but well worth the time downloading. You will find an excellent explanation of the various types of duplexers in which, at the end, he recommends this discussed configuration as the best combination of cavities to form a good duplexer. Go to this link http://www.repeater-builder.com/rbtip/ant-sys-index.html And scroll down to the article in PDF format Theory and Testing of Duplexers by Jacques Audet VE2AZX This is a large (60 pages) technical write-up that should be titled Duplexers 101. Well worth reading. 73, Tony VE3DWI ** Eric Lemmon WB6FLY gave the best response to my question of how common is it to place a bandpass fillter betweeen antenna and duplexer. Most assumed a ham repeater with tx circulator and high rejection pass/reject duplexer which is correct. About 25 years ago I had Wacom retrofit a 4 cavity bp/br 2 meter duplexer with two pass cavities. One for the receive side to provide out of band rejection and one on the transmitt side to make it ballanced looking if for nothing else. The repeater was in an area with lots of other transmitters near it. Must have been over 100 antennas in a 3 block area. Later I noticed they were offering that design in their catalog. Seems most bp/br duplexers do not really have taht much rejection of out of band signals. Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs 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/ YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [Repeater-Builder] Re: Use a band pass filter between pass-reject duplexer and antenna?
Ken Arck wrote: At 05:54 PM 7/21/2005 -0700, you wrote: I would not put a BP cavity between the duplexer and the antenna, simply because such a cavity would diminish the function of the duplexer. ---Gotta disagree with you here, Eric. Depending on the underlying problem, the addition of a single BP cavity can easily DRAMATICALLY improve the amount of isolation in a full duplex circuit. Maybe he's using a notch only type duplexer (very common I'm afraid, because of price). Maybe his xmtr makes lots of grass. I've run into this more times than I can count and a single BP cavity makes a world of difference. Preamp or no preamp in some cases. Ken Sorry, Ken-look at that again. One doesn't normally put a cavity between the output of the duplexer and the antennait would have to be broad enough to pass both tx and rx. -- Jim Barbour WD8CHL 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] Re: Use a band pass filter between pass-reject duplexer and antenna?
At 10:20 AM 7/22/2005 -0400, you wrote: Sorry, Ken-look at that again. One doesn't normally put a cavity between the output of the duplexer and the antennait would have to be broad enough to pass both tx and rx. ---Ooops! Didn't catch the between duplexer and antenna part (that's what I get for posting after serving jury duty!). You (and Eric) are absolutely correct! Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We 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] Re: Use a band pass filter between pass-reject duplexer and antenna?
Ken Arck wrote: At 10:20 AM 7/22/2005 -0400, you wrote: Sorry, Ken-look at that again. One doesn't normally put a cavity between the output of the duplexer and the antennait would have to be broad enough to pass both tx and rx. ---Ooops! Didn't catch the between duplexer and antenna part (that's what I get for posting after serving jury duty!). LOL! -- Jim Barbour WD8CHL 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] Re: Use a band pass filter between pass-reject duplexer and antenna?
DCI Makes filters for 2m/220/440 there bandwith is ONLY the amateur band. Pre-tuned they work very well for intermod rejection while passing both the TX/RX frequencies. Andy KC2GOW Start your day with Yahoo! - make it your home page YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[Repeater-Builder] Re: Use a band pass filter between pass-reject duplexer and antenna?
At 08:17 PM 7/21/2005 -, you wrote: How common is it to use a band pass filter ahead of a pass-reject duplexer, i.e., between the duplexer and feed line to antenna. Any reason for adding a band pass filter there on antenna input to duplexer vs. between the preamp pre selector cavities receiver port of duplexer. ---There are several good reasons to add an additional band pass filter, your example being one of 'em. Bottom line is that if your duplexer doesn't provide enough BP capability, it is perfectly acceptable to add additional filters/cavities. Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We 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/
[Repeater-Builder] Re: Use a band pass filter between pass-reject duplexer and antenna?
--- In Repeater-Builder@yahoogroups.com, Eric Lemmon [EMAIL PROTECTED] wrote: Without much fear of contradiction, I will state that a bandpass/bandreject duplexer has precious little bandpass effect. Sure, when you look at a response plot that covers 10 MHz, it may look very selective, but in reality the bandpass action is rather subtle. A whole lot of RF can blow through a Bp/Br duplexer in either direction, but MOST of the time this deficiency doesn't cause a problem. OK y'all, stirring the selectivity pot a little, the logical conclusion then, is that a notch duplexer is not all that bad. At least not as bad as sometimes one would believe from reading some posts here from time to time. If a plain old simplex base station can work well without ANY selectivity between it and the antenna, one could conclude, maybe, that a notch duplexer isn't so bad after all. Like I said, just stirring :) Laryn K8TVZ 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/
[Repeater-Builder] Re: Use a band pass filter between pass-reject duplexer and antenna?
At 05:54 PM 7/21/2005 -0700, you wrote: I would not put a BP cavity between the duplexer and the antenna, simply because such a cavity would diminish the function of the duplexer. ---Gotta disagree with you here, Eric. Depending on the underlying problem, the addition of a single BP cavity can easily DRAMATICALLY improve the amount of isolation in a full duplex circuit. Maybe he's using a notch only type duplexer (very common I'm afraid, because of price). Maybe his xmtr makes lots of grass. I've run into this more times than I can count and a single BP cavity makes a world of difference. Preamp or no preamp in some cases. Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We 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/
