Re: [Repeater-Builder] 2m repeater IMD issue
Let's not forget that most PAs are powered continuously, and it is the exciter that is keyed on and off. Any signal that mixes in the PA will likely be amplified at full power, regardless of whether the transmitter is on or not. In order to prevent this from happening, it is sometimes necessary to use the belt-and-suspenders approach: A dual circulator, followed by a sharply-tuned bandpass cavity or two, between the PA and the duplexer TX port. This combination limits most incoming signals to a narrow band that can be diverted into the load by the circulator. The common bandpass/bandreject (BpBr) duplexers have almost no bandpass selectivity, so this must be provided by separate bandpass-only cavities. 73, Eric Lemmon WB6FLY Someone wrote: ...What bothers me here about using a circulator is that you say it only occurs when your TX is active. This doesn't sound like IM to me, as that would occur regardless of whether the tx was active or not (IM is produced when external RF comes down the TX line and mixes in the PA stages. This does NOT require that the PA actually be making power)... 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] 2m repeater IMD issue
At 5/5/2004 05:34 PM, you wrote: Let's not forget that most PAs are powered continuously, and it is the exciter that is keyed on and off. Any signal that mixes in the PA will likely be amplified at full power, regardless of whether the transmitter is on or not. If the (class C) PA isn't being driven by the exciter, the devices will be off. In that condition, it would be rather difficult for a low-level signal (milliwatt or less) to drive the collector of an RF power transistor hard enough to cause mixing. Most all of your problems will be with your TX on. In order to prevent this from happening, it is sometimes necessary to use the belt-and-suspenders approach: A dual circulator, followed by a sharply-tuned bandpass cavity or two, between the PA and the duplexer TX port. This combination limits most incoming signals to a narrow band that can be diverted into the load by the circulator. The common bandpass/bandreject (BpBr) duplexers have almost no bandpass selectivity, so this must be provided by separate bandpass-only cavities. This is all good, though a dual isolator is overkill unless you have in-band transmitters close to your TX freq. at your site. The bandpass cavity(ies) is(are) probably the most overlooked component in a clean, neighborly system. Bob NO6B 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] 2m repeater IMD issue
With this explanation I would agree. It does sound like something on the tower. I thought, It could, not likely, be in one of the 800 transmitters. I have seen this before, and it was very strange signal. Broadband, covered most of the 130-170 MHz range, and had little birdies every 15-30 KHz ranging from -110dBm to -90dBm. Good Luck, and I would start looking at the tower... Charles Miller - Original Message - From: Richard Sharp, KQ4KX [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, May 05, 2004 9:35 AM Subject: RE: [Repeater-Builder] 2m repeater IMD issue Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. I'm wondering if the IMD is being generated somewhere on the tower, antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels of -75dBm shouldn't be a problem for the 2m tx? The harmonic filter in the tx should drop the -75 to nearly nothing - right? That's why I'm thinking perhaps the IMD is being generated somewhere else. Although, it does only occur when the 2m tx is on. tnx Richard -Original Message- From: Charles Miller Richard, You said that the IMD is only there when YOUR TX in on. If this is the case you may need an Isolator for your TX. I had a site that was getting eat alive with IMD at 150 MHz only when the TX was on. Found out that the IMD was being generated in the transmitter. Put an isolator on the thing and no more IMD. Just a thought 8-) Charles Miller - Original Message - [snip] I can see carriers appear and disappear on the rx side when the tx is on. [snip] 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] 2m repeater IMD issue
John Lloyd wrote: Several years ago, I had a similar problem with AM stations 1510 and 910 that were 600 khz apart. They were both about 5 miles away from our repeater. Our 146.94 repeater when it keyed up was hearing the audio combination of both AM transmitters that were on during the day. The problem went away at sundown when the one AM station went off the air and returned the next morning at sunrise when it came back on. We traced the IMD mix point to a guy wire anchor plate on a nearby 120 ft tower that was rusty and it wasn't even galvanized! We solved the problem by adding wire jumpers with cable clamps from each guy wire to the anchor rod which shorted out the diode action of the rusty anchor plate. John, K7JL John: We had a very similar problem in the Washington, D.C. area with our 147.00/146.40 repeater, however it was a 160 Meter dipole off the 200 foot self supporting tower about 30 to 40 feet from the duplexed repeater antenna. We raised and lowered the dipole for experimentation purposes while all were listening to duplicate the problem. All listening appreciated the education from it. You could hear the stronger of the two AM stations come and go as we raised and lowered the dipole. We went to remote receive sites instead of a duplexed repeater and never looked back! Tony, K3WX 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] 2m repeater IMD issue
Richard, That's exactly what I would do: Lower the antenna, out of the intense RF field. 73, Eric Lemmon WB6FLY Richard Sharp, KQ4KX wrote: Our club was allowed space (no cost) on top of a 400' tower using an existing 7/8 line... At the top of this tower is also six other transmit antennas that are for 800MHz trunk systems. A total of 30 channels... Of course, these antennas are in the same horizontal plane with the 2m antenna... I'm thinking of just moving the antenna about 50' down the tower (where there's no other antennas mounted) to eliminate the problem... Any thoughts? 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] 2m repeater IMD issue
It would be nice to run an intermod program to see if any combination of 800 channels produced a 'hit' near the 2M input. Ssb 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] 2m repeater IMD issue
Hello Richard, Have you tried an additional cavity in the rx path? I had a similar situation with a UHF repeater and 800 mhz systems and anadditional cavity worked for my problem. Also, do you have a preamp? If so, where in the rx path is it? You should have all the filtering ahead of the preamp. 73, Bryan -Original Message-From: Richard Sharp, KQ4KX [mailto:[EMAIL PROTECTED]Sent: Tuesday, May 04, 2004 8:04 PMTo: Repeater-Builder@yahoogroups.com; [EMAIL PROTECTED]Subject: [Repeater-Builder] 2m repeater IMD issue Hi gang, Our club was allowed space (no cost) on top of a 400' tower using an existing 7/8" line. The existing UHF antenna was replaced (by the club) with a PD220-2 (142~150 range) antenna. The coverage is very good. However, on occasion when users with HTs or during a squelch tail the IMD is audible. I have added cavity filters to both the rx tx and the IMD is still there. I've looked at it with a spectrum analyzer (connected to the rx port of the duplexer) and I do see IMD when the 2m repeater's tx is on. Although, since I have the cavity filters inline the IMD is only noticeable within the passband of the rx cavity. The IMD levels are around -90dBm give or take a couple. Ok, here's the source of the IMD. At the top of this tower is also six other transmit antennas that are for 800MHz trunk systems. A total of 30 channels. The top platform is rather large but the closest 800 antenna to the 2m antenna is about5 feet. The farthest is about 12 feet. Of course, these antennas are in the same horizontal plane with the 2m antenna. Signal levels in the 800 tx band that I see at the TX or RX port of the 2m duplexer without the bandpass cavity is about -40dBm. With the cavity about -75dBm. I'm thinking of just moving the antenna about 50' down the tower (where there's no other antennas mounted) to eliminate the problem. My thinking is that with the extreme RF levels present on the top platform that I'd have to spend a fortune in filters on the 2m equipment perhaps the 800 stuff that it'd just be cheaper to move the antenna from the top. Any thoughts? I was looking into a solution using anisolator but after further research I discovered that a VHF isolator will ALLOW RF into the 2m transmitter that is in the 800MHz range. With the bandpass cavity inline there's noVHF (150~160) or UHF (450~470)signalsthat show up on the spectrum analyzer. Only the co-site 800MHz stuff is getting through the cavity. Richard 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 the Yahoo! Terms of Service.
RE: [Repeater-Builder] 2m repeater IMD issue
Bryan, No, I don't have a preamp in the circuit - it would only make things WORSE. Well, when I add additional cavities it doesn't get rid of the IMD because it's being generated somewhere else. When I'm not using a cavity the IMD is all over the VHF band at about -90dBm. However, when the cavity is inline the IMD is only visible within the passband of the rx cavity. But it's still there - on channel basically. I can see carriers appear and disappear on the rx side when the tx is on. I'm thinking that maybe the IMD is being generated on the tower somewhere. All is the same when I have a bandpass cavity on the tx side too. Man, the 800 signals are HUGE up there! All the 800 antennas are the Celwave "Penetrator" antennas. You know, the ones that are 23ft tall and8 inches diameter, 12 - 15dB gain. Richard -Original Message-From: [EMAIL PROTECTED] Hello Richard, Have you tried an additional cavity in the rx path? I had a similar situation with a UHF repeater and 800 mhz systems and anadditional cavity worked for my problem. Also, do you have a preamp? If so, where in the rx path is it? You should have all the filtering ahead of the preamp. 73, Bryan 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 the Yahoo! Terms of Service.
Re: [Repeater-Builder] 2m repeater IMD issue
Richard, You said that the IMD is only there when YOUR TX in on. If this is the case you may need an Isolator for your TX. I had a site that was getting eat alive with IMD at 150 MHz only when the TX was on. Found out that the IMD was being generated in the transmitter. Put an isolator on the thing and no more IMD. Just a thought 8-) Charles Miller - Original Message - [snip] I can see carriers appear and disappear on the rx side when the tx is on. [snip] 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] 2m repeater IMD issue
I am suprised 800 will show passing thru in highband cavities, I would think moving down one rack is the smartest thing to try, as you noted it will be a low cost trial. Richard Sharp, KQ4KX wrote: Hi gang, Our club was allowed space (no cost) on top of a 400' tower using an existing 7/8 line. The existing UHF antenna was replaced (by the club) with a PD220-2 (142~150 range) antenna. The coverage is very good. However, on occasion when users with HTs or during a squelch tail the IMD is audible. I have added cavity filters to both the rx tx and the IMD is still there. I've looked at it with a spectrum analyzer (connected to the rx port of the duplexer) and I do see IMD when the 2m repeater's tx is on. Although, since I have the cavity filters inline the IMD is only noticeable within the passband of the rx cavity. The IMD levels are around -90dBm give or take a couple. Ok, here's the source of the IMD. At the top of this tower is also six other transmit antennas that are for 800MHz trunk systems. A total of 30 channels. The top platform is rather large but the closest 800 antenna to the 2m antenna is about 5 feet. The farthest is about 12 feet. Of course, these antennas are in the same horizontal plane with the 2m antenna. Signal levels in the 800 tx band that I see at the TX or RX port of the 2m duplexer without the bandpass cavity is about -40dBm. With the cavity about -75dBm. I'm thinking of just moving the antenna about 50' down the tower (where there's no other antennas mounted) to eliminate the problem. My thinking is that with the extreme RF levels present on the top platform that I'd have to spend a fortune in filters on the 2m equipment perhaps the 800 stuff that it'd just be cheaper to move the antenna from the top. Any thoughts? I was looking into a solution using an isolator but after further research I discovered that a VHF isolator will ALLOW RF into the 2m transmitter that is in the 800MHz range. With the bandpass cavity inline there's no VHF (150~160) or UHF (450~470) signals that show up on the spectrum analyzer. Only the co-site 800MHz stuff is getting through the cavity. Richard -- 73...Clark Beckman N8PZD 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] 2m repeater IMD issue
Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. I'm wondering if the IMD is being generated somewhere on the tower, antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels of -75dBm shouldn't be a problem for the 2m tx? The harmonic filter in the tx should drop the -75 to nearly nothing - right? That's why I'm thinking perhaps the IMD is being generated somewhere else. Although, it does only occur when the 2m tx is on. tnx Richard -Original Message- From: Charles Miller Richard, You said that the IMD is only there when YOUR TX in on. If this is the case you may need an Isolator for your TX. I had a site that was getting eat alive with IMD at 150 MHz only when the TX was on. Found out that the IMD was being generated in the transmitter. Put an isolator on the thing and no more IMD. Just a thought 8-) Charles Miller - Original Message - [snip] I can see carriers appear and disappear on the rx side when the tx is on. [snip] 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] 2m repeater IMD issue
Proper engineering also requires a Low Pass filter when installing an isolator, this will restrict any incoming frequencies above your operating frequency...although this is not the reason for the low pass filter...it is there to protect you from radiating any mixes at higher frequencies. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Politics is the art of appearing candid and completely open, while concealing as much as possible. -States: The Bene Gesserit View -Original Message- From: Richard Sharp, KQ4KX [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 05, 2004 9:35 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] 2m repeater IMD issue Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. I'm wondering if the IMD is being generated somewhere on the tower, antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels of -75dBm shouldn't be a problem for the 2m tx? The harmonic filter in the tx should drop the -75 to nearly nothing - right? That's why I'm thinking perhaps the IMD is being generated somewhere else. Although, it does only occur when the 2m tx is on. tnx Richard -Original Message- From: Charles Miller Richard, You said that the IMD is only there when YOUR TX in on. If this is the case you may need an Isolator for your TX. I had a site that was getting eat alive with IMD at 150 MHz only when the TX was on. Found out that the IMD was being generated in the transmitter. Put an isolator on the thing and no more IMD. Just a thought 8-) Charles Miller - Original Message - [snip] I can see carriers appear and disappear on the rx side when the tx is on. [snip] 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] 2m repeater IMD issue
At 10:35 AM 5/5/2004 -0400, you wrote: Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. ---What bothers me here about using a circulator is that you say it only occurs when your TX is active. This doesn't sound like IM to me, as that would occur regardless of whether the tx was active or not (IM is produced when external RF comes down the TX line and mixes in the PA stages. This does NOT require that the PA actually be making power). It sounds more like a classic case of mixing. Have you run all the freqs involved to see where the possibles might be? Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html Be sure to see our products at this year's Dayton Hamvention! Repeater Builders spaces 707 through 710 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] 2m repeater IMD issue
Maybe I'm taking to simple of a view, but could this be some sort of harmonic? However, if my math is correct (and it usually isn't... :-p ) that would be about a 4th order harmonic, I think. (If that's even possible.) Or am I all wet? Mark - N9WYS -Original Message- From: Richard Sharp, KQ4KX [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 05, 2004 9:35 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] 2m repeater IMD issue Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. I'm wondering if the IMD is being generated somewhere on the tower, antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels of -75dBm shouldn't be a problem for the 2m tx? The harmonic filter in the tx should drop the -75 to nearly nothing - right? That's why I'm thinking perhaps the IMD is being generated somewhere else. Although, it does only occur when the 2m tx is on. tnx Richard -Original Message- From: Charles Miller Richard, You said that the IMD is only there when YOUR TX in on. If this is the case you may need an Isolator for your TX. I had a site that was getting eat alive with IMD at 150 MHz only when the TX was on. Found out that the IMD was being generated in the transmitter. Put an isolator on the thing and no more IMD. Just a thought 8-) Charles Miller - Original Message - [snip] I can see carriers appear and disappear on the rx side when the tx is on. [snip] 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] 2m repeater IMD issue
-Original Message- From: Ken Arck ---What bothers me here about using a circulator is that you say it only occurs when your TX is active. This doesn't sound like IM to me, as that would occur regardless of whether the tx was active or not (IM is produced when external RF comes down the TX line and mixes in the PA stages. This does NOT require that the PA actually be making power). Good point. Yes, it only occurs when the 2m repeaters tx is on. Basically, what I see on the spectrum analyzer (connected to the rx port of the duplexer) is several signals coming and going within the passband of the rx cavity (+/- 300kHz approx). I can tune the analyzer to a specific carrier and hear either voice traffic or control channel. All of these signals are around -90dBm at the rx port. As soon as the 2m transmitter is turned off the carriers on the rx port disappear. It sounds more like a classic case of mixing. Have you run all the freqs involved to see where the possibles might be? At this point no. However, I'm in the process of obtaining all of the 800 freqs to do a calc. 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] 2m repeater IMD issue
This may not exactly fit the circumstances of the current thread. However... I was getting 800 MHz trunking interference on my 447.200 repeater receiver some years ago. I was using a WP 678- R2 duplexer and a Hamtronics LNG-450 preamp on an Exec II. The thing was, there were no 800 MHz station transmitters within five miles of the repeater site. Anyway, it seems that enough of the 800 MHz signals made it through the duplexer pass cavities to cause mixing in the preamp. In the end, the Exec II was really sensitive enough standing alone. I also once knew a fellow who used an LNG-450 on one of his MASTR Pro 460 MHz community repeaters. He had interference from a co-located two-meter repeater. In the end, the ham repeater had to go away. For him, that was more economical from both a time and expense standpoint than solving the problem otherwise. The bottom line is.. Where preamps are concerned.. Caveat Emptor! Steve, AA5SG - Original Message - From: Richard Sharp, KQ4KX [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, May 05, 2004 10:01 AM Subject: RE: [Repeater-Builder] 2m repeater IMD issue -Original Message- From: Ken Arck ---What bothers me here about using a circulator is that you say it only occurs when your TX is active. This doesn't sound like IM to me, as that would occur regardless of whether the tx was active or not (IM is produced when external RF comes down the TX line and mixes in the PA stages. This does NOT require that the PA actually be making power). Good point. Yes, it only occurs when the 2m repeaters tx is on. Basically, what I see on the spectrum analyzer (connected to the rx port of the duplexer) is several signals coming and going within the passband of the rx cavity (+/- 300kHz approx). I can tune the analyzer to a specific carrier and hear either voice traffic or control channel. All of these signals are around -90dBm at the rx port. As soon as the 2m transmitter is turned off the carriers on the rx port disappear. It sounds more like a classic case of mixing. Have you run all the freqs involved to see where the possibles might be? At this point no. However, I'm in the process of obtaining all of the 800 freqs to do a calc. 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] 2m repeater IMD issue
Duplexers with one loop in UHF do not do much at 800 Mhz - have 4 repeaters with WP678's on 2 antennas, abt 10 ft from 800 SMR transmit antenna - horizontal - ended up placing decibel band pass 2 loop cans in front of each receiver - to keep 800 from really desensensing the 460 recs. Uniden 460 LTR system and Johnson 800 VX trunking systems on the Alico Building in Waco, TX. Ssb 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] 2m repeater IMD issue
At 11:52 AM 5/5/2004 -0500, you wrote: Duplexers with one loop in UHF do not do much at 800 Mhz - ---He was talking about VHF circulators not being effective at preventing 800 Mhz energy from passing back down the TX line? I've never heard of this before. Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html Be sure to see our products at this year's Dayton Hamvention! Repeater Builders spaces 707 through 710 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] 2m repeater IMD issue
Take a tracking generator and sweep a Wacom 678 duplexer and look beyond 440 / 450 on up to 600 and beyond. If memory is correct a single cavity will have less than 10 db attenuation at 800. Ssb 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] 2m repeater IMD issue
At 12:34 PM 5/5/2004 -0500, you wrote: Take a tracking generator and sweep a Wacom 678 duplexer and look beyond 440 / 450 on up to 600 and beyond. If memory is correct a single cavity will have less than 10 db attenuation at 800. ---I said CIRCULATOR, not DUPLEXER :-) Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html Be sure to see our products at this year's Dayton Hamvention! Repeater Builders spaces 707 through 710 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/
