I'm sure if you looked at it on a spectrum analyzer you'd see the signal occupies a wide band of frequencies, hence it's probably susceptible to interference on a wide range of frequencies.
Greg On Jan 8, 2009, at 12:54 AM, Marlon K. Schafer wrote: > OK, can we put this in plain English? What freq. does 100meg > ethernet in > full or half duplex???? > marlon > > ----- Original Message ----- > From: "Josh Luthman" <[email protected]> > To: "WISPA General List" <[email protected]> > Sent: Wednesday, January 07, 2009 9:07 PM > Subject: Re: [WISPA] FM radio station site strangeness > > >> With 100BASE-TX hardware, the raw bits (4 bits wide clocked at *25 >> MHz* at >> the MII) go through 4B5B <http://en.wikipedia.org/wiki/4B5B> binary >> encoding >> to generate a series of 0 and 1 symbols clocked at *125 MHz* symbol >> rate<http://en.wikipedia.org/wiki/Symbol_rate>. >> The 4B5B encoding provides DC equalization and spectrum shaping >> (see the >> standard for details)[*citation >> needed<http://en.wikipedia.org/wiki/Wikipedia:Citation_needed> >> *]. Just as in the 100BASE-FX case, the bits are then transferred >> to the >> physical medium attachment layer using >> NRZI<http://en.wikipedia.org/wiki/NRZI>encoding. However, 100BASE-TX >> introduces an additional, medium dependent >> sublayer, which employs MLT-3 <http://en.wikipedia.org/wiki/MLT-3> >> as a >> final encoding of the data stream before transmission, resulting in a >> maximum "fundamental frequency" of* 31.25 MHz*. The procedure is >> borrowed >> from the ANSI X3.263 FDDI >> <http://en.wikipedia.org/wiki/FDDI>specifications, with minor >> discrepancies. >> [3] <http://en.wikipedia.org/wiki/Fast_Ethernet#cite_note-mlt3-2> >> >> Source: http://en.wikipedia.org/wiki/Fast_Ethernet >> Josh Luthman >> Office: 937-552-2340 >> Direct: 937-552-2343 >> 1100 Wayne St >> Suite 1337 >> Troy, OH 45373 >> >> Those who don't understand UNIX are condemned to reinvent it, poorly. >> --- Henry Spencer >> >> >> On Thu, Jan 8, 2009 at 12:02 AM, Marlon K. Schafer >> <[email protected]>wrote: >> >>> So far all I can find on the internet is that ethernet is at >>> either 12.5 >>> or >>> 31.25mhz. NOT 350, that's gigE, not 10/100. >>> >>> Also, this tower is a 100' wooden pole. Can't move anywhere really. >>> marlon >>> >>> ----- Original Message ----- >>> From: "Adam Goodman" <[email protected]> >>> To: "WISPA General List" <[email protected]> >>> Sent: Wednesday, January 07, 2009 9:15 AM >>> Subject: Re: [WISPA] FM radio station site strangeness >>> >>> >>>> It also sounds like there is a new leak in the waveguide. One more >>>> thing you might try is to move the cable from leg to leg on the >>>> tower >>>> so that you variable length sections that do not resonate at >>>> 350MHz or >>>> ~100MHz (FM transminssion). >>>> >>>> >>>> On Wed, Jan 7, 2009 at 11:16 AM, Adam Goodman <[email protected]> >>>> wrote: >>>>> We also colocate with an FM transmitter. Only 1300W though. we >>>>> also >>>>> had interference on our Ethernet lines. We solved it by moving >>>>> radios >>>>> away from the FM antenna (3 feet or so on a 90' tower) We also >>>>> installed ferrits which helped (I actually used a conduit pipe). >>>>> Grounding the cat5 helped too. >>>>> >>>>> I would think that if you find that you need more shielding. put >>>>> all >>>>> your cat5 cables in a conduit and install abreakout box at the >>>>> top of >>>>> the tower. If your area is prone to electrical storms (where isn't >>>>> these days?!) you will at some point be very sorry you didn't >>>>> grount >>>>> (and well!!) >>>>> >>>>> >>>>> >>>>> On Wed, Jan 7, 2009 at 10:47 AM, Marlon K. Schafer < >>> [email protected]> >>>>> wrote: >>>>>> Hi All, >>>>>> >>>>>> I think we finally have this all figured out. Now I just have to >>> figure >>>>>> out >>>>>> how to fix it. >>>>>> >>>>>> We've been up there for over 6 years now. It's certainly been a >>>>>> problematic >>>>>> site though. Constant channel changes (we have 3 competitors a >>>>>> mile >>>>>> away >>>>>> and pick up hundreds of ap's from in town) are the norm. >>>>>> >>>>>> This fall (a month or two ago) one of the tenants left the >>>>>> building. >>>>>> This >>>>>> cleared out most of the hardware that was in there. A little bit >>> before >>>>>> that I replaced an Inscape Data and a smartBridges combo with a >>>>>> single >>>>>> MT >>>>>> access point, using one of the cables that had been working for >>>>>> one >>>>>> of >>>>>> the >>>>>> other two. >>>>>> >>>>>> About a week ago things started to really act up. Multiple >>>>>> devices >>> were >>>>>> having trouble. I was able to catch it in the act finally. This >>>>>> time >>>>>> the >>>>>> problem wasn't a wireless issue, the devices were constantly >>>>>> disconnecting >>>>>> and reconnecting at the switch level. >>>>>> >>>>>> I pulled the Cisco switch out and dropped in a Netgear unit. >>>>>> That >>>>>> didn't >>>>>> fix it. Next I put in a Digital Loggers rack mount reboot >>>>>> device. >>> That >>>>>> wouldn't connect right either. >>>>>> >>>>>> I finally had to pull all of the hardware off of the shelf and >>>>>> set >>>>>> most >>>>>> of >>>>>> it on the floor (or just let it hang there) to get it working >>>>>> at all >>>>>> well. >>>>>> Still not perfect but better. >>>>>> >>>>>> I had by now hiked up there through sometimes knee deep snow 3 >>>>>> or 4 >>>>>> times. >>>>>> Next I took a motorbike with studded snow tires up and got >>>>>> permission >>> to >>>>>> turn down the power to the radio station. That didn't fix the >>>>>> problem >>>>>> either. >>>>>> >>>>>> Next I borrowed a snowmobile and hauled some help and my spectrum >>>>>> analyzer >>>>>> up. I was unable to see any signals that didn't belong. >>>>>> >>>>>> Next day, another hike up the hill. >>>>>> >>>>>> OK, maybe a cat 5 cable went bad and I'm getting backfeed >>>>>> through the >>>>>> switch. DC current or something. So I started testing the >>>>>> cables >>>>>> that >>>>>> run >>>>>> to the most problematic units. Well now, look at that. Bad >>>>>> cable. >>>>>> In >>>>>> fact >>>>>> there are three of them. Hmmm, kinda strange though. All >>>>>> three have >>>>>> the >>>>>> exact same fault! Oh well, better change them out anyway. I ran >>>>>> three >>>>>> new >>>>>> cable runs and just for kicks I tested one of them. What the >>>>>> heck????? >>>>>> The >>>>>> new cable has the EXACT same fault as the old one! Even though >>>>>> it >>>>>> didn't >>>>>> follow the exact same path as the old cables. >>>>>> >>>>>> Man, this is sure looking like a problem caused by the radio >>>>>> station. >>> I >>>>>> was >>>>>> using indoor cat5 and didn't run lightning protection or ground >>>>>> anything. >>>>>> Yeah I know, but remember that this has been there for a very >>>>>> long >>>>>> time >>>>>> like >>>>>> this. And as a guy with an electrical background I know that >>>>>> there >>>>>> are >>>>>> actually two ways to deal with stray electrical. Grounding is >>>>>> one. >>>>>> Insulating is another!!!! Anyway, I know it wasn't built to >>>>>> specs. >>>>>> >>>>>> I added some grounding and that didn't help at all. >>>>>> >>>>>> Yesterday I finally had one of the local wireless companies (Day >>>>>> Wireless) >>>>>> that mainly does VHF radios, backhaul etc. They also checked >>>>>> things >>>>>> with >>>>>> the spectrum analyzer but couldn't find anything amiss. I was >>>>>> able >>>>>> to >>>>>> duplicate the wiring fault for them (with my Ideal tester). But >>>>>> suddenly >>>>>> everything cleared right up! Stuff was looking good, no cable >>>>>> fault >>>>>> etc. >>>>>> Pings were looking good, devices were finally negotiating the >>>>>> connections >>>>>> right etc. >>>>>> >>>>>> I called the radio station to ask if I could try turning the >>>>>> power >>>>>> down >>>>>> again to see if we see any change on the spectrum analyzer. They >>>>>> said >>>>>> they >>>>>> thought that I'd already done that because the showed the power >>>>>> was >>>>>> way >>>>>> down. Turns out someone in the building had bumped a breaker and >>>>>> shut >>>>>> down >>>>>> part of the transmitter! Well, we got all of that figured out >>>>>> and >>> guess >>>>>> what. All of the problems came right back! I then turned the >>>>>> power >>>>>> back >>>>>> down and they cleared up. >>>>>> >>>>>> Tip for you guys, dropping an 18,000 watt system down by even >>>>>> 60% of >>>>>> it's >>>>>> normal output isn't always enough. We had to drop down to 10 >>>>>> to 20% >>>>>> to >>>>>> get >>>>>> the problems to clear up. The guys from Day Wireless had some >>>>>> small >>>>>> ferrite >>>>>> beads with them so we stuck them onto the cables. Put the >>>>>> beads on >>>>>> and >>>>>> the >>>>>> radios would negotiate at 100full. Take them off and they'd drop >>>>>> right >>>>>> back >>>>>> to 100 half. Duplicatable all day long. >>>>>> >>>>>> Soooo, current theory is that the radio station is screwing up my >>>>>> cat5 >>>>>> connections. The fact that the building has less hardware in >>>>>> it and >>>>>> we >>>>>> have >>>>>> more snow up there than normal has probably caused some different >>>>>> eddy >>>>>> currents or multipath. Or some other such strangeness. >>>>>> >>>>>> I have some shielded cable and connectors on the way. I have >>> permission >>>>>> to >>>>>> move my gear from one side of the building to the other side. >>>>>> I've >>>>>> got >>>>>> more >>>>>> high end ferrite beads on the way (one that is made for cat 5 >>>>>> and is >>> big >>>>>> enough for three wraps to go through it). Not the little $.50 >>>>>> ones, >>>>>> these >>>>>> are nearly $6.00 each. >>>>>> >>>>>> I also have a Fluke DTX on the way. >>>>>> >>> http://www.flukenetworks.com/fnet/en-us/products/DTX+CableAnalyzer+Series/ >>>>>> They rent for $650 per month from http://www.trs-rentelco.com/ >>>>>> List >>> is >>>>>> over >>>>>> $7000. If I like it I'll probably get one and add it to my two >>> spectrum >>>>>> analyzers and my bucket truck. grin >>>>>> >>>>>> Never ever forget that wireless is 50% science and 62% black >>>>>> magic! >>>>>> >>>>>> I am quite hopeful that the new cable, beads on bother ends of >>>>>> the >>> cat5, >>>>>> better grounding, and an equipment move will fix this site up >>>>>> nicely. >>>>>> If >>>>>> not, who wants to buy it? lol Seriously, this site and one of >>>>>> the >>> ones >>>>>> that it feeds cause nearly 80% of my trouble calls. With any >>>>>> luck it >>>>>> wasn't >>>>>> wireless trouble that I've been having all along. Shrug. >>>>>> >>>>>> Here's the really strange part to all of this. The hardware that >>>>>> cost >>>>>> the >>>>>> most has the most trouble! grrrr >>>>>> >>>>>> Also, the Day Wireless guy had some kind of wide band sensor. He >>>>>> could >>>>>> move >>>>>> it around and see where overall signal levels were unsafe for >>>>>> people. >>>>>> Right >>>>>> beside a 4" or so copper pipe that the radio station used as a >>>>>> wave >>>>>> guide >>>>>> was pretty bad. A couple of inches from it was ok. The next >>>>>> highest >>>>>> readings at the whole site? RIGHT a the BASE of the 100' >>>>>> wooden pole >>>>>> that >>>>>> everything is mounted on! And what did I do when I installed all >>>>>> this >>>>>> new >>>>>> gear a year ago? Yeah, I put the antennas up top and the radios >>>>>> right >>>>>> down >>>>>> at the base of the tower so I could get to them without having to >>>>>> rent >>> a >>>>>> lift. Dang the luck! >>>>>> >>>>>> Hope that this helps someone else out. >>>>>> marlon >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>> -------------------------------------------------------------------------------- >>>>>> WISPA Wants You! 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