I didn't have any problem with the strobe noise until the internet gear desensed my receiver. It is not being retransmitted. They are powering their tower top equipment by sending the DC on the CAT5 Cable. Wouldn't such a long run greatly attenuate the power available to the tower top equipment? The installation is untidy. No attempt to cut the CAT5 wire to length. I can only guess how much extra cable he has at the top. I am no longer able to climb towers so I can't inspect the tower top installation. The strobe is new it was installed last summer after the old one failed. Thanks for the help.
Jim WK5Y ----- Original Message ----- From: Jacob Suter To: [email protected] Sent: Monday, April 27, 2009 6:16 PM Subject: RE: [Repeater-Builder] Computer noise in 2M Repeater As a wireless installer with a little RF knowledge, I can tell you *nothing* is a bigger piece of crap than anything Netgear sells. I'd also guess this WISP also loses a lot of gear based on what you've mentioned so far. I'd have to suggest to them the following: A> Cisco makes nice switches on the cheap (most WISP POPs don't use more than a 100mbit switch anyways, you can get a Cisco Catalyst 2924 for under $50 off ebay, and it's a much higher quality switch with a good power supply that won't spew RF noise) B> Shielded cat5/5e/6 bonded to Mot R56 standards. This will further eliminate RF spew while greatly reducing lightning failures. Personally, I'm a big fan of running DC over coax (I use super-cheap RG59, bonded to R56 standards) and *FIBER* for the data. DC is easy to protect (MOVs and poly-fuses are your friends), Ethernet is much harder. Fiber is awesome, easy and cheap. Lightning doesn't affect it, which is a huge bonus. Ethernet<->Fiber transceivers can be had for pennies on the dollar these days, especially if you only need 10 or 100mbit. Their noise source may also be the power supply feeding the system. Assuming they're not using a PoE-capable switch, they most likely have a 'power injector' inline, connected to some sort of power supply. I've discovered most cheap-o ('Mean Well' is a personal favorite) 'project' brick power supplies have somewhat dirty output. The long Ethernet run either increase the noise or work as a much better antenna. 0.1uF capacitors and ferrites in the correct places can greatly reduce this (or using better quality power supplies). Now. the strobe problem you're describing sounds like a potential horrible electrical problem at the site. In my experience an FM rig shouldn't be greatly affected by a strobe. It also shouldn't be causing a problem/reaction with the WISP gear (it may be causing damage to it!) so I'd definitely find out what is going is going on with the strobe. Good luck! Jacob Suter From: [email protected] [mailto:[email protected]] On Behalf Of Jim Russell Sent: Saturday, April 25, 2009 8:53 PM To: [email protected] Subject: Re: [Repeater-Builder] Computer noise in 2M Repeater Thanks for the input from all of you. I went to the tower site this afternoon to give another look at the problem. The noise has gotten worst. Our receiver is greatly desensed. The only equipment on site is the site owner's UHF repeater, our two meter repeater and the Internet equipment. The site owners equipment doesn't seem to be affected. The strobe lamp puts a buzz in our receiver each time it fires. I noticed one of the green lamps on the Netgear switch get brighter when the strobe fires. I'm sure the Internet equipment is affected by that. The two meter is our primary machine used in our storm watch activities. I tried to contact the Internet company today with no answer. Will try again Monday. Again thanks for the information. Jim WK5Y ----- Original Message ----- From: Eric Lemmon To: [email protected] Sent: Saturday, April 25, 2009 9:15 AM Subject: RE: [Repeater-Builder] Computer noise in 2M Repeater Jim, This situation happens all too often, and it usually occurs because cheap equipment is used (plastic boxes to contain the amplifier, unshielded cable, no ferrites, ineffective grounding. etc.) to keep the installation costs down. This is a misguided approach, because repeated visits to fix a leakage problem will always cost a lot more than a first-class system would have cost. Sound familiar? Another possible factor is that *some* wireless installers are primarily IT (Information Technology) folks who have relatively little experience with the RF environment at a repeater site. I have met a few of these clueless guys, whose eye glaze over when I talk about an interfering carrier from a CPU crystal or intermodulation. They're used to installing APs and bridges in office buildings, and don't see anything different about tie-wrapping a more powerful box to a tower that supports many other services, except perhaps using some electrical tape and silicone goop to waterproof the connectors. Don't laugh- it happens! So, to answer your question, immediately contact the wireless system owner and advise him that his system is interfering with yours, and it must be fixed promptly. Don't quote the FCC rules quite yet. If the polite approach does not get results, contact the site owner. Above all, do not just sit and wring your hands. The wireless owner must comply with Part 15 rules, but he must be told if there is a problem. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Russell Sent: Friday, April 24, 2009 7:20 PM To: [email protected] Subject: [Repeater-Builder] Computer noise in 2M Repeater Does anyone have any suggestions on how to eliminate noise generated by a Wireless Internet System. The owner of the tower where our club has our 145.370 MHz repeater has rented space to a group who have mounted a wireless Internet "relay" on the tower. The system is simple, it consist of a Netgear switch, a Microwave dish and a smallYagi. There is approx. 300 feet of Cat 5 wire going up and 300 feet coming down the tower. Their antennas are mounted within a few feet of ours on the top of the 260 ft. tower. We unplugged the netgear switch and the noise cleared, we disconnected our antenna and the noise goes away. The noise rides on the repeater receiver squelch tail. We do use a PL tone or we wouldn't be able to use our repeater at all Jim WK5Y
