Grids are that and therefore only good for CPE installs or sites where no other units needs co located. They don't belong on a back haul because it's to important. Good panels or solid dishes should be the only antennas used for a back haul.
/Eje Sent via BlackBerry from T-Mobile -----Original Message----- From: "Mike" <m...@aweiowa.com> Date: Sat, 27 Feb 2010 22:02:03 To: 'WISPA General List'<wireless@wispa.org> Subject: Re: [WISPA] Some days the rats win Grids are RF sieves. They spew RF to the sides, and the back. They have a lot of forward gain, so work well in most cases. You'd be better off putting a panel, or better yet a solid dish at that site. Start with one. If it doesn't work a lot better, change the other. You can also try offsetting one of the antennas from the pole -- in front or behind the other laterally. Mike -----Original Message----- From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf Of MDK Sent: Saturday, February 27, 2010 12:45 PM To: WISPA General List Subject: [WISPA] Some days the rats win On Thursday, I set about to fix a link that's performing badly. It was just re-pointed and working really, REALLY bad. Somewhat intermittently, but still REALLY bad. I had already tried new radios at each end. So far, no luck. I tried a new pigtail on the low end, as well, still... No luck. I replaced the whole board and radio setup at the low end, no luck. After much watching what it did and when, I came to the conclusion it was self interference. Not on the same frequency, but I noticed that way up the pole was another antenna with the same polarization and it was almost exactly the same aim and polarization - I'm thinking I'm overloading the radio with signal. So, I decided that I'd switch from Hor to Ver, on this link, figuring it would reduce the self interference. So, I went to the low end (down in the valley, 4 miles) and installed a new antenna, pointed it right, and real quick, switched the cable over to it. After a slight re-pointing, it worked fine, slightly better than the old antenna, which is an ancient Equinox. Cool. But no fix for the link's issues. So, I pulled the antenna down, switched it over to Vertical and put it back up. It was a clear, 55 degree day, sunshine. Could see perfectly. Drove to the hill site, put a mount on the pole, and installed another antenna, about 3- 4 feet below the original, other side of the telephone pole it's on, and in Vertical, as well. Doug got on one end, me on the other and synchronized over the cell phone, we switched the antenna cables over. No signal. Now, it was brilliant daylight, crystal clear air, sunshine, and we can literally SEE the building and pole from the other end. I re-aimed my end, swapped again. No signal. Doug changed the dipole at his end, to one I had JUST REMOVED from a working antenna (took the antenna apart, but the antenna had been working 3 hours before). No signal. I changed the dipole on my end. No signal. I changed the whole antenna. No signal. Doug changed dipoles yet again to a new one off the shelf. No signal. Original antennas are fine ,and the signal is around -64. I grab another grid - one I had JUST REMOVED from service (replaced it with a higher gain panel), HAND HOLD it while standing on the ladder and point it to the other end. -89 is the best we can get. So the other end is the problem, right? Check the antenna taken off the far end. Works fine. Mind you, we're 4 miles apart. We can see the other end standing on the ground. We can see it in great detail through binoculars. There are no buildings, trees, bushes, or other obstructions. The land slopes away from the hill end, and other end is 16 feet off the ground, angle uptilt is about 1 degree. There is NO possible fresnel zone encroachment at either end, even if you're standing, holding the antenna at chest height at the hillside end. So, what's wrong? I don't know, and I can't figure it out. Nobody has stuff pointed at the higher end. The other end is 270 degrees shielded by heavy trees, metal roof buildings, hills, etc, and has always showed zilch for noise, though the hillside shows some. There's nothing but sky behind the hillside site. Nothing to point to. No reason for anyone to build a high gain beam pointing its way, and certainly there's nothing for at least 9 miles aside from my own customers that could possibly be pointing that way. I have twice checked to make sure both are Vertical. They are. Each time, we put the cables back to the original antennas and the link comes up. I moved the low end accidently, and we gained slightly. But, the antennas are obvious visually aimed. And the replacement on the low end is HIGHER than the original. Almost 4 feet higher. The low end antenna is now the one I had working in Hor polarization. The upper antenna was new, and I replaced the dipole with another new. And then I replaced the whole antenna with a used one I had just removed the day before, from a working customer's site. I've gotten the link to work reasonably well, by reducing power on the short link (far end) and reducing power on the NEAR end (other link, 2.5 X longer), and using Star-OS thresholds, so it ignores the higher level, but out of band signals it sees. So, my self interference diagnosis is pretty much correct. So, which one is bad? Yes, I lowered the hillside end, but it's 8 feet up, and the ground slopes downward starting at the pole. There's no chance we're even within 2X the fresnel zone to the ground, which is dirt and a little wheat stubble. The handheld one didn't work lower or higher, so I doubt it's a height issue. Tilt has been checked and re-checked, and is NOT off any significant amount. I've been trampled by the rats and I can't get up... HELP! ---------------------------------------------------------------------------- ---- WISPA Wants You! 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