I used to do a lot of weird stuff to get sites to work with -48V DC with +48V equipment involving isolated grounding. It all works as long as you know what you are doing and you are the only one who works on it. It just doesn’t scale well. Far cheaper in the long run to put in an isolated DC/DC convertor, mark the -48V buss, the +48V buss, and the +24V buss and hook up equipment to that its ground reference is what it expects it to be. The techs at the sites don’t have to know as much and are much less likely to blow something up wiring it backward or accidentally ground the +48 to the -48 through the internal wiring or some piece of equipment.
Mark > On Nov 25, 2018, at 8:08 AM, Ken Hohhof <af...@kwisp.com> wrote: > > That said, there is always a way to give the equipment the power it wants. > Even if you have a mix of equipment at a site that wants +24, -48 and +48, > it’s just some extra power supplies or DC-DC converters and maybe some > reduced power conversion efficiency. I still have a lot of sites with 24V to > 24V DC-DC converters because I wasn’t sure some Ubiquiti or Mikrotik > equipment would run off 27V from the batteries and I needed regulated 24V. > Maybe it would have been OK, but in the grand scheme of things, it wasn’t a > lot of money and space to stick a little Traco DIN rail DC-DC converter in > the cabinet. Same thing with 24VDC sites that I upgraded with a licensed > backhaul that wanted 48V so I bolted in a Mean Well RSD. I think I’d buy > some extra electronics before I’d rely on plywood insulators. But then you > gotta do what you gotta do to make it work, and it’s hard to argue if it > works. > > From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com>> On Behalf > Of Chuck McCown > Sent: Saturday, November 24, 2018 3:53 PM > To: AnimalFarm Microwave Users Group <af@af.afmug.com > <mailto:af@af.afmug.com>> > Subject: Re: [AFMUG] 48v Power Supply Switches > > One of the larger problems are that there are so many people working in this > field that do not have a clear understanding of what –48 and ground > referenced power supplies actually mean. I answer questions about this every > single week from customers using our POE injectors. > > Almost any source or load will work if the voltage is right. You may have to > put insulators between your antenna and the tower but you can generally > figure out something that will work. I have mounted solar charge controllers > on plywood to isolate the from grounds in –48 VDC off grid applications. > > > > From: Forrest Christian (List Account) > Sent: Saturday, November 24, 2018 2:03 PM > To: AnimalFarm Microwave Users Group > Subject: Re: [AFMUG] 48v Power Supply Switches > > The 450i and 450m don't really care about polarity. That's one of the > reasons that the cambium sync products we sell work with either voltage. > The older radios expected +24v with the negative side grounded. > > Other radios can be hard to track down. I can confirm that many nowadays > use an isolated supply inside so that they don't care if one of the rails are > grounded as long as you respect the voltage and polarity into the radio. But > others are very much incompatible with either positive or negative ground > systems. > > > > On Sat, Nov 24, 2018, 10:11 AM Ken Hohhof <af...@kwisp.com > <mailto:af...@kwisp.com> wrote: >> Some WISP equipment like Packetflux started with +24V and extended the >> voltage range so now it can be powered via +48/56V. >> >> It’s a little difficult to pin down some radios, it seems like most 802.3af >> equipment is actually floating and as long as you observe polarity, either >> side of the power supply can be grounded. Documentation usually doesn’t >> say. Also some Mikrotik equipment may say -48V in the spec sheet but the >> terminals are just labeled + and – and seems to be floating just like >> 802.3af. Cambium/Ceragon has a DC powered POE that seems happy with +24, >> -48 or +48 input. My belief has always been that Cambium radios like 450i >> and 450m want +48V POE but maybe they don’t care. The Cambium POE brick >> actually has a 2 pin AC power cord and no ground terminal, implying that the >> power source can be floating. I wish manufacturers weren’t so vague about >> this. >> >> From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com>> On >> Behalf Of Chuck McCown >> Sent: Saturday, November 24, 2018 9:41 AM >> To: AnimalFarm Microwave Users Group <af@af.afmug.com >> <mailto:af@af.afmug.com>> >> Subject: Re: [AFMUG] 48v Power Supply Switches >> >> I guess my experience is the reverse. Having spent 40 years in telecom, >> seems that almost everything rack mounted is –48 if you want DC power. I >> don’t recall ever finding +48 rack mounted telecom equipment. >> >> From: Ken Hohhof >> Sent: Saturday, November 24, 2018 7:43 AM >> To: 'AnimalFarm Microwave Users Group' >> Subject: Re: [AFMUG] 48v Power Supply Switches >> >> I have one site with an Eltek/Valere system and it does its job quite >> nicely, my question for you: how do you deal with the Eltek Systems mostly >> being designed for -48 yet a lot of the equipment ISPs use wants +48? My >> one Eltek site has an old Purewave WiMax basestation that I am about to >> decommission but I will need +48 and I don’t want to put in a DC-DC >> converter if nothing will be running off the -48. >> >> From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com>> On >> Behalf Of Chuck McCown >> Sent: Saturday, November 24, 2018 8:13 AM >> To: AnimalFarm Microwave Users Group <af@af.afmug.com >> <mailto:af@af.afmug.com>> >> Subject: Re: [AFMUG] 48v Power Supply Switches >> >> +1 >> >> Sent from my iPhone >> >> On Nov 24, 2018, at 3:13 AM, Gino A. Villarini <g...@aeronetpr.com >> <mailto:g...@aeronetpr.com>> wrote: >> >>> We go direct to Eltek/valere -48 system. It has redundant rectifiers, >>> web/snmp and LVD >>> >>> Gino Villarini >>> Founder/President >>> @gvillarini >>> t: 787.273.4143 <tel:787.273.4143> >>> m: >>> <http://www.aeronetpr.com/> >>> <https://www.inc.com/profile/aeronet> >>> <https://www.facebook.com/aeronetpr/> >>> <https://www.instagram.com/aeronetpr/?hl=en> >>> <https://www.linkedin.com/company/aeronet-broadband-corp> >>> >>> <https://twitter.com/AeroNetPR?ref_src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Eauthor> >>> >>> <https://www.youtube.com/channel/UCr2Q9WBrAYVm3Fn970Jd6VA> >>> www.aeronetpr.com <http://www.aeronetpr.com/> | Metro Office Park #18 Suite >>> 304 Guaynabo, PR 00968 >>> From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com>> on >>> behalf of Alex Davidson <al...@pdmnet.net <mailto:al...@pdmnet.net>> >>> Reply-To: AnimalFarm Microwave Users Group <af@af.afmug.com >>> <mailto:af@af.afmug.com>> >>> Date: Friday, November 23, 2018 at 11:13 AM >>> To: "af@af.afmug.com <mailto:af@af.afmug.com>" <af@af.afmug.com >>> <mailto:af@af.afmug.com>> >>> Subject: [AFMUG] 48v Power Supply Switches >>> >>> Hey guys, we are stepping up to some 48v equipment on a tower and in >>> looking into power supply switches. This seemed to be something that would >>> work for us (Mean Well SE-1000-48). Any thoughts or pros and cons that yall >>> have found with this unit. Any units of similarity that might work well in >>> place of this one. Thanks >>> >>> >>> >>> -- >>> AF mailing list >>> AF@af.afmug.com <mailto: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 <mailto: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 <mailto: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 <mailto: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 <mailto:AF@af.afmug.com> > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > <http://af.afmug.com/mailman/listinfo/af_af.afmug.com>
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