If you ever do the experiment again, it would be interesting to rotate the antenna to see if there’s some kind of sidelobe pointed toward the ground or something. Obviously you can’t install it rotated or upside down (unless you really trust that cable gland to seal against rain), but it would be interesting to see the results. Like you said, maybe some component in the feed horn is blocking the RF.
Cambium is in a better position to investigate this, it’s disappointing if they aren’t taking it seriously. From: AF <af-boun...@af.afmug.com> On Behalf Of Mark Radabaugh Sent: Thursday, March 28, 2019 6:19 AM To: AnimalFarm Microwave Users Group <af@af.afmug.com> Subject: Re: [AFMUG] [*] corrective optics On Mar 27, 2019, at 10:11 PM, Ken Hohhof <af...@kwisp.com <mailto:af...@kwisp.com> > wrote: In another thread, Mark Radabaugh posted: “For your next product…. Corrective optics for 450B high gain CPE!” Mark, I’m not sure if you were serious, I suspect yes. Yes - but I’m not sure what is possible with the design. I know it’s frustrating that the antenna gain is lower than the old reflector dish, Cambium dropped the number on the spec sheet to 24 dBi, but I think even that is optimistic, I think it’s about 2 dB less than the old combo which was supposed to be 25 dBi. Lower antenna gain is going the wrong way! I don’t care if it does have higher xmt power, that does nothing for the downstream direction. Changing the spec sheet to match what they ended up with was a pretty big cop out when the product failed to meet design expectations. In calling for corrective optics, do you have any info or even a gut feel for whether the problem is in the feed or the dish? Is it as simple as the dish is just too small? I suspect that they managed to block part of the antenna feed horn with other components. Also, is it just the gain is low, or does the 450b hi gain have other issues? Like poor F/B or sidelobe performance or something? It seems like if the 450b high gain is far away from other surfaces it works mostly to spec but when mounted in the typical locations near rooftops it seems like it either picks up more destructive multipath interference than previous designs or the antenna pattern distorts badly. For a long time I thought they didn’t manage to get the feedhorn in the focus of the dish but Cambium assures me that it’s right. We are seeing decent performance under 5 miles but it seems to fall apart much quicker over 5 miles than would be expected. We set up a test with the bucket truck and drove it out and measured every mile to 10 and it came back fine - but that was 50’ in the air with nothing around. Yet swapping out standard 450 SM’s with beehive or KP dishes with 450B’s at >5 miles routinely fails with poor signal. The difference is often far more than the 2dB the spec sheets would indicate. Sometimes it works if the antenna is well away from all other surfaces like on a tower but for the majority of installs the swap fails. Why were we doing that anyway? We wanted to start using 5.1/5.2. I know the 450b mid-gain is frustrating because apparently Cambium doesn’t think a tight vertical pattern is important. I keep wondering if a top and bottom flap like on the old 2.4 Stingers would correct that. Cambium seems to be sharing antenna designs between ePMP and 450, so the same issues probably exist in the corresponding ePMP products. -- AF mailing list <mailto:AF@af.afmug.com> AF@af.afmug.com <http://af.afmug.com/mailman/listinfo/af_af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
-- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
