It’s 17.5 inches and it doesn’t perform like 26 dBi, so I guess that means not a good feed?
Smelly cat, smelly cat, what are they feeding you? What if it’s just shaped like a Cassegrain feed but actually the tube is stuffed full of electronics and they have a couple of PCB dipoles at the end or something like that? Would that hurt antenna gain? I’ve been puzzled how the 450b can have higher xmt power than the old SM yet fit inside the feed tube, you’d think there would be a problem with heat dissipation. From: AF <[email protected]> On Behalf Of [email protected] Sent: Thursday, March 28, 2019 4:19 PM To: 'AnimalFarm Microwave Users Group' <[email protected]> Subject: Re: [AFMUG] [*] Re: [*] corrective optics A 17.5” reflector with a good feed should have about 26 dBi. From: Ken Hohhof Sent: Thursday, March 28, 2019 3:08 PM To: 'AnimalFarm Microwave Users Group' Subject: Re: [AFMUG] [*] Re: [*] corrective optics It’s around 18.5 inches but the actual reflector part is 17.5 inches, with a 0.5 inch flat area all around the edge. From: AF <[email protected] <mailto:[email protected]> > On Behalf Of [email protected] <mailto:[email protected]> Sent: Thursday, March 28, 2019 2:43 PM To: 'AnimalFarm Microwave Users Group' <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] [*] Re: [*] corrective optics Thanks, that helped a bunch. It is like a Rocket. Could be over illumination, under illumination or just too small of a reflector for the gain. What is the diameter of the reflector? Looks like it is about 20 inches or so. Someone take a hammer and break open the feed and snap a photo for me.... save the pieces so you can glue it back together later... From: Ken Hohhof Sent: Thursday, March 28, 2019 1:26 PM To: 'AnimalFarm Microwave Users Group' Subject: Re: [AFMUG] [*] Re: [*] corrective optics I’m busy configuring a licensed link or I’d snap a photo. But here’s a Cambium video of assembling a 450b high gain, maybe you can glean enough from this. Note that there is an optional radome that snaps onto the front of the dish, they don’t show it in the video, but some of us like the radomes for aesthetics/windload/snow. https://www.youtube.com/watch?v=z88P-0nZkZ8 <https://www.youtube.com/watch?v=z88P-0nZkZ8&feature=youtu.be> &feature=youtu.be From: AF <[email protected] <mailto:[email protected]> > On Behalf Of [email protected] <mailto:[email protected]> Sent: Thursday, March 28, 2019 1:54 PM To: 'AnimalFarm Microwave Users Group' <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] [*] Re: [*] corrective optics Yes, I could probably google it, but I would like to have an image of the SM and reflector or whatever that is underperforming. From: Ken Hohhof Sent: Thursday, March 28, 2019 12:17 PM To: 'AnimalFarm Microwave Users Group' Subject: Re: [AFMUG] [*] Re: [*] corrective optics I think he meant a photo of a Cambium 450b, or something relevant to improving the antenna performance thereof. What were you thinking the topic was about? From: AF <[email protected] <mailto:[email protected]> > On Behalf Of Carl Peterson Sent: Thursday, March 28, 2019 1:05 PM To: AnimalFarm Microwave Users Group <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] [*] Re: [*] corrective optics "What would you like to see?" I'm OK with the spam, but if this thread goes the wrong way I might need to unsubscribe. No offense, just not my bag. On Thu, Mar 28, 2019 at 11:06 AM Mark Radabaugh <[email protected] <mailto:[email protected]> > wrote: What would you like to see? Mark On Mar 28, 2019, at 10:26 AM, Chuck McCown <[email protected] <mailto:[email protected]> > wrote: How about some photos. Sent from my iPhone On Mar 28, 2019, at 6:58 AM, Ken Hohhof <[email protected] <mailto:[email protected]> > wrote: 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 <[email protected] <mailto:[email protected]> > On Behalf Of Mark Radabaugh Sent: Thursday, March 28, 2019 6:19 AM To: AnimalFarm Microwave Users Group <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] [*] corrective optics On Mar 27, 2019, at 10:11 PM, Ken Hohhof <[email protected] <mailto:[email protected]> > 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 [email protected] <mailto:[email protected]> <http://af.afmug.com/mailman/listinfo/af_af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- Carl Peterson PORT NETWORKS 401 E Pratt St, Ste 2553 Baltimore, MD 21202 (410) 637-3707 _____ -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com _____ -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com _____ -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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