RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mike, I think the next step would be to try to get the paging operator to install an isolator on the output of his VHF pager for a temporary check. If he has one already, he could try putting two in tandem to increase the rejection of any RF coming back down the feedline from his antenna. What you may be hearing is a mix in his VHF transmitter with something else in his vicinity with an unstable frequency that is sweeping the mix through the VHF band. Years ago we had a problem in the Dallas area with a welder that produced an unstable carrier that would sweep through the 2 meter input frequencies of the repeaters in the area. The welder was located on the upper floors of the building in progress, and had a nice site for radiating the interfering signal. A foxhunt tracked that one down but it did not go away till the building was completed. Good luck with your QRM. 73 - Jim W5ZIT --- On Wed, 10/28/09, Mike Besemer (WM4B) mwbese...@cox.net wrote: From: Mike Besemer (WM4B) mwbese...@cox.net Subject: RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band To: Repeater-Builder@yahoogroups.com Date: Wednesday, October 28, 2009, 7:03 PM Strangely enough, I happen to be an O-O (as is the another club member, who sponsors the 145.110 repeater… which is also being interfered with) and have been in touch with our coordinator. He’s been very helpful in urging us along and providing us guidance (or reassurance) that we’re going about this the right way. He’s also indicated that he’s willing to go to ARRL HQ with it if we need to and then let them go lateral to the FCC. We had a great experience with Laura Smith about a year ago when we needed help convincing a banned user to stay off our systems. It took one letter to her (complete with recordings) and one phone call to get our banned user a nice letter from Laura reminding him that he really couldn’t afford to pay what she was prepared to charge him for using our repeater! So… I think that, armed with enough ammunition, we can go that route. However, I REALLY don’t want to. The fellow who owns the paging company has tried to work with us, and although it’s not going as fast as we’d like, I understand that he’s got a different motivation than we do. Aside from that, he helped us out with a professional climbing crew a couple of years ago, got us a good deal on a DB-224, and cut us a break on some hardline and connectors. The bottom line is, it’s not a relationship we want to end through a Federal intervention! That being said, I HAVE reminded him that he’s admitted that we’re carrying his data on our repeater, and whether or not it’s his equipment at fault or somebody else’s, HE’S going to be the first person they come looking for and it’ll be a terrible pain in his butt… and wallet. He acknowledges that fact. So… while I’d like for him to do some things differently… I get where he’s coming from and I appreciate that he’s helped as much as he has. On the other hand, if it turns out to be equipment that belongs to another company… I’ll drop a dime in a heartbeat if I don’t get satisfaction from them! 73, Mike WM4B From: Repeater-Builder@ yahoogroups. com [mailto:Repeater- buil...@yahoogro ups.com] On Behalf Of Paul Plack Sent: Wednesday, October 28, 2009 7:48 PM To: Repeater-Builder@ yahoogroups. com Subject: Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band Mike, the interference is clearly not caused by your own rusty roof, and is both eggregious and easily documented. I know we hate to go there unless it's a last resort, but I'll bet the FCC is almost as tired of non-compliant pager systems as we are. Perhaps that technique would prove motivating. - Original Message - From: Mike Besemer (WM4B) To: Repeater-Builder@ yahoogroups. com Sent: Wednesday, October 28, 2009 5:34 PM Subject: RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band I’m with ya on your third paragraph. We’ve worked well together so far, but we have very different techniques and motivations. .. .
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Joe, The problem isn't traffic dependant (10 am being a busy time), as I monitor on and off all day and there is PLENTY of traffic all day long. It seems to have more to do with temperature. You can clearly hear the signals come on and fade off frequency. It's also easy to hear which transmitter is sending the pages. I have two dual band radios in my vehicle. Typically one is on the repeater output, one on the input, one of VHF paging and one on UHF paging. It's also been confirmed by having the owner send test bursts by specific transmitters. The other two UHF frequencies are also paging transmitters. Good thoughts about the transmitter self-oscillating when unkeyed... that's another road we can go down. Speaking of going down roads. what I really need is more help! Several of our club members are engaged in assisting, but what I really need is a dedicated team of folks. Having to work for a living is taking a serious bite out my tracking time! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe Sent: Wednesday, October 28, 2009 11:51 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band Hello Mike. The first clue is that the signal is moving up and down the 2 meter band. This would tell me that something not frequency controlled is causing the interference. Not frequency controlled would mean that the transmitter is not crystal or GPS locked to a specific frequency. Now, something that is frequency controlled may be involved with the IMD mix, but the signal that is free running is possibly causing an IMD mix to drift. I have seen this happen in a PA when it was NOT transmitting. We had a case of a paging transmitter PA that would go into self oscillation when it was not keyed by the exciter. The PA had power to it at all times and it would create interference when it was idle. Some random thoughts: Your paging company signal may be mixing with it, but they may not be the culprit. 10AM can be busy time for a paging company, so the fact that it happens around that time would not be unusual. How do you know the data is from a specific paging company? Did you listen to their signal and the interference at the same time? Is it exactly the same? He says that he has remote control of the transmitters. What happens when he shuts them both off? As someone else pointed out, does he have a link frequency that he ties the sites together with? The link transmitter may be causing the interference, or be part of the RF mix. An IMD program will be useless to figure the IMD of a drifting transmitter that is part of a mix. You said 462.850 and 462.925 are also involved. What is on those frequencies? Who is on these frequencies and how are they involved? A lightning hit may have caused this all to happen. In my last job I troubleshooted lots of interference. You really need to take an antenna and directional find the source of the interference. It is time consuming, but will lead you to the physical source of the interference. Don't be fooled that it is positively the paging companies fault, as it may just be a mix in some other service PA. The last one I found was interference on a 53.85 Mhz repeater. At first, the culprit seemed to be the NOAA weather station on 162.55Mhz. NOAA weather audio was coming through the repeater crystal clear. It turned out to be a telemetry station PA that was mixing 4 X 53.85 - 162.55 = 52.85Mhz. The mix was exactly on the input! The telemetry station was owned by the water company that allowed us on the site, so we ended up moving the repeater to 53.71Mhz. We could have pushed the water company to fix their equipment, but probably would have been asked to leave the site. Sometimes diplomacy rules. I worked for paging companies for quite awhile and know that they get a bad rap, probably rightfully so for the most part. This sounds like the paging company is willing to work with you. My gut feeling is that you are going to find something else causing the problem. Again, diplomacy rules. 73, Joe, K1ike Mike wrote: A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. T
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Joe, I was told (caveat) that he verified the spectrum after the interference started. Since he's investing quite a bit of time into helping clear this up, I have to believe he's done that. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of MCH Sent: Wednesday, October 28, 2009 11:51 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band I have to wonder how he can say his stuff is clean when this just started a couple weeks ago. Did he perform a PM check within the last two weeks? Unlikely. Stuff can go south in a minute, and seldom just before you check it. Joe M. Paul Plack wrote: Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - *From:* Mike mailto:mwbese...@cox.net mailto:mwbesemer%40cox.net *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com *Sent:* Wednesday, October 28, 2009 12:28 PM *Subject:* [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... . -- Internal Virus Database is out of date. Checked by AVG - www.avg.com Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09 05:58:00
Re: {Disarmed} Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
A while back in time, I worked 20 miles south of Chapel Hill, NC. During the late morning and afternoon our vhf fire, low band EM, and a UHF carrier squelch sheriff mutual aid channels starting getting garbage that was noisy but occurred on the various channels from 47 mhs to 453 mhz. A paging transmitter on 152 mhz at the UNC Hospital was the cause. An additional transmitter had been put in an equipment room on the top floor of the hospital,. When the roof heated up, along with the extra heat from the added transmitter, the older paging transmitter started sending spurs all over the place. Cooling the equipment room caused the problem to go away. Marv, WA4NC Glenn Little WB4UIV wrote: Locally, years ago, we had a military transmitter that had a wandering spur. I am near Charleston, SC. The spur was strong enough to key up amateur radio repeaters in the two meter band from Wilmington, NC to Savannah, Ga. The offender turned out to be a 250 Watt base station used to cover approximately 10 Acres. The radio was a Motorola MICOR. The service shop could not fix the problem, so, they replaced the transmitter. This may be a spur from a transmitter. The spur that we experienced wandered up the band, then, down the band. The wander was slow enough that you could hear it approaching the repeater input frequency as a weak off frequency signal. It would wander through the passband of the repeater in about 30-45 seconds and again sound like a weak off frequency signal as the squelch closed. The repeater was either in the 148 or the 150 MHz range and interfered with a 146.79, 146.82, 146.88 and a 149.94 MHz repeater. It took about a week to get the problem taken care of. The military had tried to classify the frequency of the repeater on this base due to the type of traffic that they handled. Kind of hard to hide what you are doing when transmitting in the clear with that much power and having a spur keying up repeaters over the distance that this one did. There is some software that allows finger printing of a transmission base on the lockup signature and oscillator stability as seen on the transmitted signal. You could possibly compare the known probable offender with the offender through one of the interfered with repeaters or it's input frequency. Wish you well with resolving the problem. 73 Glenn WB4UIV At 11:51 PM 10/28/2009, you wrote: I have to wonder how he can say his stuff is clean when this just started a couple weeks ago. Did he perform a PM check within the last two weeks? Unlikely. Stuff can go south in a minute, and seldom just before you check it. Joe M. Paul Plack wrote: Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - *From:* Mike mailto:mwbese...@cox.net mailto:mwbesemer%40cox.net *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com *Sent:* Wednesday, October 28, 2009 12:28 PM *Subject:* [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... . -- Internal Virus Database is out of date. Checked by AVG - www.avg.com Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09 05:58:00 Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
This sounds like a problem I traced about 20 years ago on a VHF paging system. The PA was tube and there was some issue the tech had with the PA not firing on rf drive .. so he locked the PTT to the PA on all the time and then just turned the exciter on and offThe problem was the PA was self resonant +- a sweep of our freq and would go there whenever the transmitter exciter was NOT present... and it drifted with temperature so was a 300 w moving target I guess he never looked at it with a watt meter while the exciter was off How we finally identified it was we could hear the tone blips at the end of the interference cycle ( when the station was really being asked to tx) bleed through from the PURC tones just before it went away.. We then watched the TX carrier of the real tx come on perfectly synchronouslyto the absence on our end...By watching what came on when it went off we figured out the freq... as there was no modulation during interference...They toggled perfectly on a wide sweep spectrum analyzer... During the day it was gone as the system was busy.. but at night when it got quiet we got hammered...Then I DF'ed the particular tx.as it was a simulcastAnd the tech shut it down until it could be fixed correctly and our problem went away The tone sequencing leaked through from the link system which pointed us to paging... in this case it was a 152 . to protect the guilty :-) and moved to 151. area blocking some control stations inputs at a nearby dispatch center... Doug KD8B At 06:28 PM 10/28/2009, you wrote: Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - From: mailto:mwbese...@cox.netMike To: mailto:Repeater-Builder@yahoogroups.comRepeater-Builder@yahoogroups.com Sent: Wednesday, October 28, 2009 12:28 PM Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... .
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mike- On Thu, 29 Oct 2009 05:33:10 -0500, Mike Besemer (WM4B) mwbese...@cox.net wrote: I was told (caveat) that he verified the spectrum after the interference started. Since he's investing quite a bit of time into helping clear this up, I have to believe he's done that. A few years ago we had a similar problem, except the pager location/ID was unknown. It took almost 2 years to find it, and one phone call to the pager to fix it. The final proof was standing outside the fence with one radio listening to the pager traffic and one on our repeater. After the pager traffic QUIT, the PA started the spur on our input. The statement above could well be true, as most people think of spectrum verification as being while transmitting. In our case the temperature involved was outdoor temp, in the range of 10-25 degrees F, causing it to drift through our input passband into another repeater's passband, which further complicated the foxhunt aspect, hi! In your case, you are hearing the traffic as well, which suggests a mix to me. You might juggle the numbers a bit and see what freq would give you an interfering mix. It could be generated in the owner's idle PA (as someone above suggested ) or a totally foreign TX. As the owner seems pretty cooperative, eliminating both his TX's should be pretty easy, If you were really lucky, it would be his idle PA mixing with his active PA and the site of the fix would be in sight! (Sorry -couldn't resist that one.) Good Luck!! Dick W0RFX -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mike Besemer (WM4B) wrote: Joe, The problem isn’t traffic dependant (10 am being a busy time), as I monitor on and off all day and there is PLENTY of traffic all day long. It seems to have more to do with temperature. You can clearly hear the signals come on and fade off frequency I had thought that you said that 10AM seemed to be a particularity bad time of interference. 10AM does not seem to be a time that the heat load of a site would be high. If the site was overheating, I would think that interference would be worse in the afternoons. It’s also easy to hear which transmitter is sending the pages. I have two dual band radios in my vehicle. Typically one is on the repeater output, one on the input, one of VHF paging and one on UHF paging. It’s also been confirmed by having the owner send test bursts by specific transmitters. OK, important question. Is the particular paging company you are working with to resolve the problem ALWAYS involved in the interference? The other two UHF frequencies are also paging transmitters. How are the other two UHF frequencies involved in the interference? When the two UHF freqs are involved, is the above mentioned paging company ALSO involved? Good thoughts about the transmitter self-oscillating when unkeyed... that’s another road we can go down. I would guess that if the interference is caused by an self-oscillating transmitter, it would be probably be in the VHF range of frequencies. That way the signal could get out of the transmitter through any filtering that may be involved. Just a guess, mind you. Speaking of going down roads… what I really need is more help! Several of our club members are engaged in assisting, but what I really need is a dedicated team of folks. Having to work for a living is taking a serious bite out my tracking time! Someone needs to do some directional finding on the interfering signal, then triangulate. If I were to guess at a location I would look up the the geographical location in your area of all the frequencies involved. 152.480, 462.775, 462.850 and 462.925Mhz. You may find that they share the same location or are very close to each other. Start looking there. Or go to the site that the paging company is at and look for interference. You said that you are on a water tank. Water tanks are notorious for co-site interference because all of the antennas are usually on the top of the tank and are in the same horizontal plane. In other words, no vertical separation. Keep this in mind as I found my problem at our water tank site by momentarily shutting down the water company telemetry radio (with their permission) and the interference went away. The problem was that the VHF telemetry antenna and the 6 meter ham antenna were only about 10 feet apart. 73, Joe, K1ike 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...@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] Pager Interference to 2-meter VHF Public Service Band
On Thu, Oct 29, 2009 at 1:45 PM, Joe wrote: Mike Besemer (WM4B) wrote: Joe, The problem isn’t traffic dependant (10 am being a busy time), as I monitor on and off all day and there is PLENTY of traffic all day long. It seems to have more to do with temperature. You can clearly hear the signals come on and fade off frequency I had thought that you said that 10AM seemed to be a particularity bad time of interference. 10AM does not seem to be a time that the heat load of a site would be high. If the site was overheating, I would think that interference would be worse in the afternoons. As I mentioned, the interferrence is moving. At a certain temperature, it sweeps through our repeater input. As the temperature rises, it seems to move on. It’s also easy to hear which transmitter is sending the pages. I have two dual band radios in my vehicle. Typically one is on the repeater output, one on the input, one of VHF paging and one on UHF paging. It’s also been confirmed by having the owner send test bursts by specific transmitters. OK, important question. Is the particular paging company you are working with to resolve the problem ALWAYS involved in the interference? No, but being the strongest signals in the area, they are the primary source of frustration. The other two UHF frequencies are also paging transmitters. How are the other two UHF frequencies involved in the interference? When the two UHF freqs are involved, is the above mentioned paging company ALSO involved? Not necessarily Good thoughts about the transmitter self-oscillating when unkeyed... that’s another road we can go down. I would guess that if the interference is caused by an self-oscillating transmitter, it would be probably be in the VHF range of frequencies. That way the signal could get out of the transmitter through any filtering that may be involved. Just a guess, mind you. Speaking of going down roads… what I really need is more help! Several of our club members are engaged in assisting, but what I really need is a dedicated team of folks. Having to work for a living is taking a serious bite out my tracking time! Someone needs to do some directional finding on the interfering signal, then triangulate. If I were to guess at a location I would look up the the geographical location in your area of all the frequencies involved. 152.480, 462.775, 462.850 and 462.925Mhz. You may find that they share the same location or are very close to each other. Start looking there. Or go to the site that the paging company is at and look for interference. Working it. Not getting nearly enough help though. You said that you are on a water tank. Water tanks are notorious for co-site interference because all of the antennas are usually on the top of the tank and are in the same horizontal plane. In other words, no vertical separation. Keep this in mind as I found my problem at our water tank site by momentarily shutting down the water company telemetry radio (with their permission) and the interference went away. The problem was that the VHF telemetry antenna and the 6 meter ham antenna were only about 10 feet apart. We're the only one on the site. 73, Joe, K1ike 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...@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] Pager Interference to 2-meter VHF Public Service Band
There are at least two transmitters at two sites... not likely they're all bad. But... the owner has assured me they're clean and I haven't seen anything hokey on the spectrum analyzer from the repeater site. Mike WM4B On Wed, Oct 28, 2009 at 2:46 PM, dmur...@verizon.net wrote: Did you look a the output of the paging transmitters with a spectrum analyzer? Oct 28, 2009 06:29:13 PM, Repeater-Builder@yahoogroups.com wrote: A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and unstable. What am I missing here? Mike WM4B Messages in this topic (2) Reply (via web post) | Start a new topic Messages |Files | Photos |Links | Members Yahoo! Groups Change settings via the Web (Yahoo! ID required) Change settings via email: Switch delivery to Daily Digest
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Sounds like a bad case of mixing products (i.e. 2A-B) where A is frequency A and B is frequency B. Several years ago, I helped cure a similar problem on 146.820 MHz. Turned out four transmitters were involved in that fracas and it only took two to start the repeater howling. 152.480 is one of the common paging frequencies. There is another around 157 MHz that is usually a troublemaker for 2m amateur repeaters. A lot paging transmitters are NOT properly filtered. I have run across some that were connected directly to the feedline and antenna with no circulator, no isolator, nothing. This is unacceptable practice. No transmitter or receiver should be looking directly into a feedline at any fixed site where multiple transmitters are in operation or, where interference could likely erupt. I doubt the UHF paging transmitters has a whole lot to do with the problem although there is a slim chance they might. Chances are, the VHF transmitter is the one involved. The next thing I'd be curious about, given the paging company's comments about the ability to key the transmitters separately, is this: How are they getting the data from their offices to the transmitters? By radio link? By wireline? or both? If by radio, therein may lie the second transmitter in the mix. If not, keep searching. One thing to keep in mind with the spectrum analyzer is that it is not likely as sensitive as the repeater's receiver. Some spec an's are pretty sensitive, others not so sensitive. So you may want to visit the paging site with it and see what you find. Especially around 304.960 MHz which is the double of 152.480 MHz. KC5DBH Matt From: Mike mwbese...@cox.net To: Repeater-Builder@yahoogroups.com Sent: Wed, October 28, 2009 1:28:56 PM Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and unstable. What am I missing here? Mike WM4B Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Good question about how the data was getting to both transmitter sites. I've been meaning to ask that question and keep forgetting. I'll report back. Mike WM4B On Wed, Oct 28, 2009 at 3:16 PM, Matt Harker wrote: Sounds like a bad case of mixing products (i.e. 2A-B) where A is frequency A and B is frequency B. Several years ago, I helped cure a similar problem on 146.820 MHz. Turned out four transmitters were involved in that fracas and it only took two to start the repeater howling. 152.480 is one of the common paging frequencies. There is another around 157 MHz that is usually a troublemaker for 2m amateur repeaters. A lot paging transmitters are NOT properly filtered. I have run across some that were connected directly to the feedline and antenna with no circulator, no isolator, nothing. This is unacceptable practice. No transmitter or receiver should be looking directly into a feedline at any fixed site where multiple transmitters are in operation or, where interference could likely erupt. I doubt the UHF paging transmitters has a whole lot to do with the problem although there is a slim chance they might. Chances are, the VHF transmitter is the one involved. The next thing I'd be curious about, given the paging company's comments about the ability to key the transmitters separately, is this: How are they getting the data from their offices to the transmitters? By radio link? By wireline? or both? If by radio, therein may lie the second transmitter in the mix. If not, keep searching. One thing to keep in mind with the spectrum analyzer is that it is not likely as sensitive as the repeater's receiver. Some spec an's are pretty sensitive, others not so sensitive. So you may want to visit the paging site with it and see what you find. Especially around 304.960 MHz which is the double of 152.480 MHz. KC5DBH Matt ___ From: Mike mwbese...@cox. net To: Repeater-Builder@ yahoogroups. com Sent: Wed, October 28, 2009 1:28:56 PM Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Dirty paging TX. Seen that many times. Joe M. Mike wrote: A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and unstable. What am I missing here? Mike WM4B Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mixing products generally don't sweep through the spectrum, as usually both TXs are stable and the mix would be as well. Joe M. Matt Harker wrote: Sounds like a bad case of mixing products (i.e. 2A-B) where A is frequency A and B is frequency B. Several years ago, I helped cure a similar problem on 146.820 MHz. Turned out four transmitters were involved in that fracas and it only took two to start the repeater howling. 152.480 is one of the common paging frequencies. There is another around 157 MHz that is usually a troublemaker for 2m amateur repeaters. A lot paging transmitters are NOT properly filtered. I have run across some that were connected directly to the feedline and antenna with no circulator, no isolator, nothing. This is unacceptable practice. No transmitter or receiver should be looking directly into a feedline at any fixed site where multiple transmitters are in operation or, where interference could likely erupt. I doubt the UHF paging transmitters has a whole lot to do with the problem although there is a slim chance they might. Chances are, the VHF transmitter is the one involved. The next thing I'd be curious about, given the paging company's comments about the ability to key the transmitters separately, is this: How are they getting the data from their offices to the transmitters? By radio link? By wireline? or both? If by radio, therein may lie the second transmitter in the mix. If not, keep searching. One thing to keep in mind with the spectrum analyzer is that it is not likely as sensitive as the repeater's receiver. Some spec an's are pretty sensitive, others not so sensitive. So you may want to visit the paging site with it and see what you find. Especially around 304.960 MHz which is the double of 152.480 MHz. KC5DBH Matt *From:* Mike mwbese...@cox.net *To:* Repeater-Builder@yahoogroups.com *Sent:* Wed, October 28, 2009 1:28:56 PM *Subject:* [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
I would look at the exciter freq on the uhf paging transmitter. It would help with some info on the paging transmitters. Model and such. -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mike Sent: Wednesday, October 28, 2009 1:29 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and unstable. What am I missing here? Mike WM4B Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - From: Mike To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 28, 2009 12:28 PM Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... .
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Paul, I'm with ya on your third paragraph. We've worked well together so far, but we have very different techniques and motivations. Right now, my motivation is to make is stop before I go crazy. I'm hearing paging tones in my sleep! I kinda think one of the sites took a lightning strike about the time this started (we had a pretty good lightning event about that time), so I think the PA is a good possibility. Or an isolator/combiner. I'd like to have the first whack with a baseball bat when we find it! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack Sent: Wednesday, October 28, 2009 6:29 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - From: Mike mailto:mwbese...@cox.net To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 28, 2009 12:28 PM Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... . http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId= 95309/stime=1256754552/nc1=4025338/nc2=5191953/nc3=5741393
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Ya'll know as much as I do about what the paging equipment is. I'm working with limited knowledge. only what gets passed on to me from the owner. I'll ask about that, as well as the exciter frequencies. From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin King Sent: Wednesday, October 28, 2009 6:02 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band I would look at the exciter freq on the uhf paging transmitter. It would help with some info on the paging transmitters. Model and such. -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Mike Sent: Wednesday, October 28, 2009 1:29 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. The repeater itself is an Advanced Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans. The feedline is 7/8 hardline feeding a DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This system has been in service for years and has never given us any problems, and we are the only ones at the site. To be clear, the interference we are experiencing is clearly audible on the repeater input. I have the capability to monitor via telephone and have heard it on the receiver, and I've also traveled to the site and heard the interference on my mobile radio hooked to the repeater antenna. The interference is also audible on the input in various locations around town. Also, the interference can be heard on the input regardless of whether or not the repeater transmitter is on. It also continued to be present during several days of continuous heavy rain. The interference typically shows up at least once a day, although some days (rarely) it does not show up at all and other days it will show up several times. Lately, it's been making an appearance around 10 a.m. and hangs around for an hour or two. As it begins to disappear, it sounds as though it is moving off frequency. This interference has also been heard on at least two other repeaters in the area. One is about 22 air-miles from the 146.85 machine and is on 145.110 (-600 KHz). It has also been heard on or near the output frequency of that machine, and one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission. The other repeater it has been heard on is 147.300 (+600 KHz). I also have reports from a neighboring county a ham/deputy sheriff there has been hearing it on VHF public safety frequencies. As you can see, it's all over the place. I've been working with the owner of a local paging company and we can clearly tell that the data we're hearing is coming from 152.480 and 462.775. He has two sites (about 20 miles apart) that simulcasts on both frequencies and when those transmitters are active it's easy to tell that the data is the same. He also tells me that he can key each transmitter separately and the data from each transmitter will be heard on our repeater. We also believe that there are other systems on nearby frequencies that are being heard on our repeater, specifically 462.850 and 462.925. I've run IMD numbers on everything I can think of, but can't come up with a common thread. For it to be moving all through the 2-meter band and for it to be mixing with several different frequencies, it seems to me that it's got to be very ugly and unstable. What am I missing here? Mike WM4B Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Mike, the interference is clearly not caused by your own rusty roof, and is both eggregious and easily documented. I know we hate to go there unless it's a last resort, but I'll bet the FCC is almost as tired of non-compliant pager systems as we are. Perhaps that technique would prove motivating. - Original Message - From: Mike Besemer (WM4B) To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 28, 2009 5:34 PM Subject: RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band I'm with ya on your third paragraph. We've worked well together so far, but we have very different techniques and motivations... .
RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Strangely enough, I happen to be an O-O (as is the another club member, who sponsors the 145.110 repeater. which is also being interfered with) and have been in touch with our coordinator. He's been very helpful in urging us along and providing us guidance (or reassurance) that we're going about this the right way. He's also indicated that he's willing to go to ARRL HQ with it if we need to and then let them go lateral to the FCC. We had a great experience with Laura Smith about a year ago when we needed help convincing a banned user to stay off our systems. It took one letter to her (complete with recordings) and one phone call to get our banned user a nice letter from Laura reminding him that he really couldn't afford to pay what she was prepared to charge him for using our repeater! So. I think that, armed with enough ammunition, we can go that route. However, I REALLY don't want to. The fellow who owns the paging company has tried to work with us, and although it's not going as fast as we'd like, I understand that he's got a different motivation than we do.Aside from that, he helped us out with a professional climbing crew a couple of years ago, got us a good deal on a DB-224, and cut us a break on some hardline and connectors. The bottom line is, it's not a relationship we want to end through a Federal intervention! That being said, I HAVE reminded him that he's admitted that we're carrying his data on our repeater, and whether or not it's his equipment at fault or somebody else's, HE'S going to be the first person they come looking for and it'll be a terrible pain in his butt. and wallet. He acknowledges that fact. So. while I'd like for him to do some things differently. I get where he's coming from and I appreciate that he's helped as much as he has. On the other hand, if it turns out to be equipment that belongs to another company. I'll drop a dime in a heartbeat if I don't get satisfaction from them! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack Sent: Wednesday, October 28, 2009 7:48 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band Mike, the interference is clearly not caused by your own rusty roof, and is both eggregious and easily documented. I know we hate to go there unless it's a last resort, but I'll bet the FCC is almost as tired of non-compliant pager systems as we are. Perhaps that technique would prove motivating. - Original Message - From: Mike Besemer (WM4B) mailto:mwbese...@cox.net To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 28, 2009 5:34 PM Subject: RE: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band I'm with ya on your third paragraph. We've worked well together so far, but we have very different techniques and motivations... . http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId= 95324/stime=1256772865/nc1=4025338/nc2=5733770/nc3=4836037
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Hello Mike. The first clue is that the signal is moving up and down the 2 meter band. This would tell me that something not frequency controlled is causing the interference. Not frequency controlled would mean that the transmitter is not crystal or GPS locked to a specific frequency. Now, something that is frequency controlled may be involved with the IMD mix, but the signal that is free running is possibly causing an IMD mix to drift. I have seen this happen in a PA when it was NOT transmitting. We had a case of a paging transmitter PA that would go into self oscillation when it was not keyed by the exciter. The PA had power to it at all times and it would create interference when it was idle. Some random thoughts: Your paging company signal may be mixing with it, but they may not be the culprit. 10AM can be busy time for a paging company, so the fact that it happens around that time would not be unusual. How do you know the data is from a specific paging company? Did you listen to their signal and the interference at the same time? Is it exactly the same? He says that he has remote control of the transmitters. What happens when he shuts them both off? As someone else pointed out, does he have a link frequency that he ties the sites together with? The link transmitter may be causing the interference, or be part of the RF mix. An IMD program will be useless to figure the IMD of a drifting transmitter that is part of a mix. You said 462.850 and 462.925 are also involved. What is on those frequencies? Who is on these frequencies and how are they involved? A lightning hit may have caused this all to happen. In my last job I troubleshooted lots of interference. You really need to take an antenna and directional find the source of the interference. It is time consuming, but will lead you to the physical source of the interference. Don't be fooled that it is positively the paging companies fault, as it may just be a mix in some other service PA. The last one I found was interference on a 53.85 Mhz repeater. At first, the culprit seemed to be the NOAA weather station on 162.55Mhz. NOAA weather audio was coming through the repeater crystal clear. It turned out to be a telemetry station PA that was mixing 4 X 53.85 - 162.55 = 52.85Mhz. The mix was exactly on the input! The telemetry station was owned by the water company that allowed us on the site, so we ended up moving the repeater to 53.71Mhz. We could have pushed the water company to fix their equipment, but probably would have been asked to leave the site. Sometimes diplomacy rules. I worked for paging companies for quite awhile and know that they get a bad rap, probably rightfully so for the most part. This sounds like the paging company is willing to work with you. My gut feeling is that you are going to find something else causing the problem. Again, diplomacy rules. 73, Joe, K1ike Mike wrote: A couple of weeks ago, our repeater system started to experience interference from a paging system. The repeater is on 146.850 (-600 KHz), with the antenna system about 120 feet up a water tower. T
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
I have to wonder how he can say his stuff is clean when this just started a couple weeks ago. Did he perform a PM check within the last two weeks? Unlikely. Stuff can go south in a minute, and seldom just before you check it. Joe M. Paul Plack wrote: Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - *From:* Mike mailto:mwbese...@cox.net *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com *Sent:* Wednesday, October 28, 2009 12:28 PM *Subject:* [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... . Internal Virus Database is out of date. Checked by AVG - www.avg.com Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09 05:58:00
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
Locally, years ago, we had a military transmitter that had a wandering spur. I am near Charleston, SC. The spur was strong enough to key up amateur radio repeaters in the two meter band from Wilmington, NC to Savannah, Ga. The offender turned out to be a 250 Watt base station used to cover approximately 10 Acres. The radio was a Motorola MICOR. The service shop could not fix the problem, so, they replaced the transmitter. This may be a spur from a transmitter. The spur that we experienced wandered up the band, then, down the band. The wander was slow enough that you could hear it approaching the repeater input frequency as a weak off frequency signal. It would wander through the passband of the repeater in about 30-45 seconds and again sound like a weak off frequency signal as the squelch closed. The repeater was either in the 148 or the 150 MHz range and interfered with a 146.79, 146.82, 146.88 and a 149.94 MHz repeater. It took about a week to get the problem taken care of. The military had tried to classify the frequency of the repeater on this base due to the type of traffic that they handled. Kind of hard to hide what you are doing when transmitting in the clear with that much power and having a spur keying up repeaters over the distance that this one did. There is some software that allows finger printing of a transmission base on the lockup signature and oscillator stability as seen on the transmitted signal. You could possibly compare the known probable offender with the offender through one of the interfered with repeaters or it's input frequency. Wish you well with resolving the problem. 73 Glenn WB4UIV At 11:51 PM 10/28/2009, you wrote: I have to wonder how he can say his stuff is clean when this just started a couple weeks ago. Did he perform a PM check within the last two weeks? Unlikely. Stuff can go south in a minute, and seldom just before you check it. Joe M. Paul Plack wrote: Mike, If it moves around based on time of day, my first guess is a PA that's gone bad, and has a parasitic that's temperature-related. If you've tracked an individual spur drifting 70 kHz up the band during a single transmission, this is not some (intentional) oscillator drifting, but some combination of failed components or tuning which has produced a parasitic. Sorry to say, but a paging transmitter owner swearing his stuff is clean is pretty meaningless. The assumption in his industry is the professionals who maintain his stuff are not the problem, it's those damn hams. Sadly, it may more often be the other way around these days, as companies maintaining paging equipment have transitioned to underpaid, under-trained card-swappers instead of component-level technicians with a clue about RF systems. 73, Paul, AE4KR - Original Message - *From:* Mike mailto:mwbese...@cox.net *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com *Sent:* Wednesday, October 28, 2009 12:28 PM *Subject:* [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band A couple of weeks ago, our repeater system started to experience interference from a paging system... ...one evening I tracked it from about 145.120 to 145.190 as it swept through each transmission... . Internal Virus Database is out of date. Checked by AVG - www.avg.com Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09 05:58:00 Yahoo! Groups Links
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
: There is some software that allows finger printing of a transmission : base on the lockup signature and oscillator stability as seen on the : transmitted signal. I am interested in such things! Anyone have any good suggestions or input regarding software or systems? Kurt
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
On Wed, 28 Oct 2009, Facility 406 DM09 wrote: I am interested in such things! Anyone have any good suggestions or input regarding software or systems? Cavity - digital storage oscilliscope. -- Kris Kirby, KE4AHR Disinformation Analyst
Re: [Repeater-Builder] Pager Interference to 2-meter VHF Public Service Band
I'd use a really fast spectrum analyzer, meaning an analog one and point a video camera at it On Wed, Oct 28, 2009 at 10:19 PM, Kris Kirby k...@catonic.us wrote: On Wed, 28 Oct 2009, Facility 406 DM09 wrote: I am interested in such things! Anyone have any good suggestions or input regarding software or systems? Cavity - digital storage oscilliscope. -- Kris Kirby, KE4AHR Disinformation Analyst Yahoo! Groups Links
