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. .. .
[Repeater-Builder] Re: Pager Interference to 2-meter VHF Public Service Band
If I have followed the thread correctly, this interference happens from either of the paging transmitters, not just one or the other. I would suggest you check to see if there is a TV linear translator very nearby it could be the source. --- In Repeater-Builder@yahoogroups.com, Mike Besemer \(WM4B\) mwbese...@... 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. 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
[Repeater-Builder] GE Icoms offered
I have 3 pair of GE IComs that I do not need. These were pulled from working radios. 3 ea 4EG25A10 UHF TX 458.05, and one 458.9 2 ea 4EG26A10 UHF RX 453.050 1 ea 4EG26A13 UHF RX 453.9 Yours for the cost of shipping.
[Repeater-Builder] Re: GE Icoms offered
I just found two more Icoms with sockets. 4EG25A10 on 455.85 and 455.45 I have 3 pair of GE IComs that I do not need. These were pulled from working radios. 3 ea 4EG25A10 UHF TX 458.05, and one 458.9 2 ea 4EG26A10 UHF RX 453.050 1 ea 4EG26A13 UHF RX 453.9 Yours for the cost of shipping.
[Repeater-Builder] Re: Helical or hybrid ring duplexer for 6m
Re: Helical or Hybrid Ring Duplexer for 6M I'm working on a theoretical design, but I need 5 Circulators. You have arrived at The Land of Impractical. Please watch your step as you exit the bus. s.
Re: [Repeater-Builder] Re: Helical or hybrid ring duplexer for 6m
A 1 rack unit duplexer for a 30-50MHz low band system is impractical vs 4 6-8 foot tall 12 cavities? On Fri, Oct 30, 2009 at 2:58 PM, skipp025 skipp...@yahoo.com wrote: Re: Helical or Hybrid Ring Duplexer for 6M I'm working on a theoretical design, but I need 5 Circulators. You have arrived at The Land of Impractical. Please watch your step as you exit the bus. s. Yahoo! Groups Links
[Repeater-Builder] Re: Experience of Helical / heliax duplexer for 6m
Hi Cruizzer I build a 6m repeater 10 years ago, 2 yrs on air, till lightning bolt toasted it. First tried spilt antennas. Lousy performance. Tried adding coax 1/4 wave stubs, but were too broad. Then built 6 cavity hybird ring helical in paint can duplexer. Worked, but tuning drifted due to temp change effecting mechanical size and shape of paint can. You could hear them expand and make a boink noise and the tuning was off severely enough to cause high insertion loss. My next effort was the coaxial heliax stubs. 4tx, 4rx, put into a plywood box, and wrapped in aluminum flashing. Stood up vertically. Think of a pack of cigarettes, 2 rows of 4. Worked like a champ with a homebrew dual 5/8 vertical. I used ceramic multi turn trimmers to tune the series coupling, notch depth / width. The lighter the coupling, the sharper the notch, but the less depth. I used same style trimmers to tweak parallel resonance of the stubs. 73 and good luck! Ed N3SDO
