Actually it is a bare ceramic patch antenna. Look at the top, you're seeing the side view.
When I got the response last time from the vendor they said they don't recommend it, and stated several reasons including if I remember correctly something about changing the dielectric constant in some odd way, detuning the antenna. We didn't get much farther than that since they didn't have a good answer about whether this was confined to certain types of coating or what... I haven't heard back from them on whether or not the latest modules or not have the same issues, but I suspect they likely do. On the other hand, it wouldn't surprise me to find that what they're concerned about isn't going to change the tuning enough to actually make a difference, and they're just being overly cautious. On Wed, Jul 22, 2020 at 7:02 AM Chuck McCown <[email protected]> wrote: > I would not expect a thin layer of conformal to bother the antenna in a > significant way. It might if you were putting it on a bare patch but that > is not the case here. > > Sent from my iPhone > > On Jul 22, 2020, at 6:53 AM, Mark Radabaugh <[email protected]> wrote: > > > > I decided to try a conformal coating on the Syncbox to see if it would > cause any problems with the GPS and avoid the corrosion issues we have > seen. We tested before and after the conformal coating with no detectable > impairment to the GPS SNR and signal level. > > Only about 16 hours so far but throwing a pitcher of water on it and > leaving the cover off all night in a rainstorm hasn’t seemed to bother it. > The picture didn’t catch the sync light but it’s happily blinking away. > There is a lot of silicon grease on/around the RJ45 which looks a bit funny > but I can’t conformal coat the jack itself for obvious reasons and I was > intending to douse this one with water. I’m sure SNR is bad right now with > a blob of water on top of the antenna but it’s picking up enough to stay in > lock. > > Going to leave it like this and give it a couple weeks to see how it holds > up, but so far so good. > > Regarding loss of sync on 450 equipment - on further examination of the > logs we are seeing issues with 450 equipment randomly losing sync or > switching to free-run and back to sync-over-power across a number of > injectors - CMM5, CTM-2, and Rackinjectors. These issues started about > the time we started deploying SyncInjectors but it’s really looking like > that is coincidental. Data is pointing toward something that changed with > the firmware rather than the injector. I have not had time yet to see if > it included the older 450 versus 450i yet. > > Mark > > <IMG_3364.jpeg> > > On Jul 13, 2020, at 10:28 PM, Forrest Christian (List Account) < > [email protected]> wrote: > > You bring up a few fair, and known, points. I'll respond to at least a > few of them: > > In relation to the water ingress, we've seen enough of these to know it's > at least an occasional issue. Especially in hotter climates, one thing > we've seen is the gasket cracking in the enclosure. I'm also not > completely convinced this isn't a water condensation/surface moisture issue > in damper climates. Our enclosure manufacture just switched the gasketing > material, perhaps as a result of our whining, to something different. > I've also looked at various alternatives for enclosures but haven't found > the right one yet. I thought I had one which would have been perfect, > until I got the $50 per unit quote in quantity. Some days I miss the > pipes, but it was time for them to go from a mostly marketing perspective. > > I've also looked at the conformal coating in the past, and the challenge > has been that the GPS module manufacture has told us this is a no-no since > it apparently changes the tuning of the GPS patch antenna. I probably > need to re-evaluate this now that there's a different patch antenna on the > new modules - but I expect a similar answer. > > For the past couple of years, I've been trying to move to a module flat on > the board and then either using a PCB antenna like is used in devices like > cell phones, where the antenna's pattern is such that mounting it flat on > vertically oriented PCB results in a vertical pattern like the patch has. > This should solve the water getting on the antenna issue, as there won't be > anything directly below the seam to leak on. The holdup has been me > trying to possibly move to a module with a different GPS chipset at the > same time, hoping that this would be better than our existing module. > With all the warts (some of which will be described below), I'm finding > that the modules/chipset that we're using is actually not that bad in > comparison to some others. I even have had an eval of a 'timing grade' > gps receiver here, which had more failures than the non-timing-grade ones > we're using. I have a few more to qualify, but look for this change in > coming months assuming I can find a suitable module and antenna which works. > > In relation to the random timing loss of lock, I am not going to disagree > with you at all. I suspect some of this might be leftovers from the > GPS+GLONASS issue from the end of the year which seems to have resolved > itself for the most part, but I know enough about that bug that it wouldn't > shock me to find that there are still lingering issues. The problem here > is that although it 'feels' like there might be more issues, I don't have > quantifiable numbers. With all of that in mind, I'm currently working on > in-field upgrade procedures for upgrading the firmware for these modules to > get them the GLONASS fix. This seems to be a more troublesome problem than > it should be, since it's just an issue of getting the right firmware - the > problem being that the company who built the firmware for these got gobbled > and the successor company tends to be more difficult to work with. I have > firmware which does work on the modules, it just isn't an official build by > the manufacturer. > > Around the end of the year, we did switch our basics to a newer module, > based on the same chipset. The Basics shipped since then default to > GPS+GALILEO. Recently we've been using this module in Aux Port and > Deluxes, but with GPS+GLONASS+Fixed-Glonass firmware since the Cambium > firmware doesn't understand (yet) the Galileo sentences. So anything you > get from us today has this latest chipset in it, and has the GLONASS fix > even if it isn't enabled. I will say that testing and in-field reports > indicates this is even more stable, not sure how much of it is because of > the increased antenna gain, and how much of it is due to the updated > firmware, or how much is just a side effect of having a lot more of the > older units in the field having customers report problems on. I know at > least some of it is measurable on the bench here, so it isn't all based on > field reports. The only downside so far is that we do see an uptick in > DoA's (but still well under 1%). Frustratingly, the DoA's we've gotten > back have somehow resurrected themselves between the field and here, but > thankfully there doesn't seem to be any increased in-field failures that we > can see other than the DoA's. > > To Eric's point about the holdover timer.. I understand the CTM2's had > this functionality built in. Nothing else I'm aware of has had that except > for some our early GPS modules which just produced a pulse no matter what, > and when it could align it it would. This was good in the early days, not > so much nowadays. > > I'm looking at a couple options to implement a holdover. First of all, > assuming the docs are correct, I can tell the GPS modules to produce sync > all the time, or only when they have a 2D lock, or when they have a 3d > lock. Sync all the time can be bad. Especially if you're not monitoring > lock status, since it means that a GPS can be out of lock but producing > sync pulses which are wildly wrong, causing all sorts of issues. 2d lock > can be bad too since it shares similar issues. As a result, the modules > default to '3d lock'. I've been toying with doing something dynamic in > the rackinjector where it is able to dynamically changes the mode, so it > waits until you get 3d lock, and then since it should have a good position, > switches to '2d lock' mode, or maybe even freerun. At the bare minimum, I > probably will allow customers to change the setting statically if they're > willing to deal with the ramifications. > > I have some other ideas I'm cooking up as well, just don't want to say too > much until I'm actually a bit farther down the path. > > > On Mon, Jul 13, 2020 at 5:57 AM Mark Radabaugh <[email protected]> wrote: > >> Forrest, >> >> As usual there are probably multiple issues going on. We have seen an >> increase in the number of DFS hits recently, and we also have a lot of >> Packetflux timing equipment on the network. I have noticed that DFS hits >> tend to be worse in ‘unusual’ hot weather conditions. And we have >> certainly seen a pretty unusual heat wave over the last few weeks. I’m not >> sure if this is just heat changing sensitivity of the DFS detections >> (temperature is involved in the RF calibration), if there is more >> reflection off the ionosphere in these weather conditions, or if the >> weather radar systems are just really jacking up power looking for storms. >> >> As far as timing - I do think there is some timing instability going on >> but I can’t pin it down to anything specific. We continue to struggle >> with RackInjectors losing the GPS timing signal from the Syncbox Basic >> during or after storm events. Typical symptom in the RackInjector fails >> to see sync from the syncbox and the AP’s go into freerun. Sat’s in view, >> etc. all look normal, just no pulses. Sometimes a power cycle from the >> RackInjector will fix it, sometimes physically unplugging it will fix it, >> and sometimes you just have to wait. I have instructed the field crews >> multiple times to make absolutely sure they screw in every screw tight on >> the syncbox but I’m not 100% sure they are doing that. I have seen at >> least one come back to the shop with evidence of water damage to the GPS >> board at the top. I would really like to see the extra step of conformal >> coating on the boards if there isn’t a reliable way of keeping water off of >> them. >> >> We have also been seeing an unusual number of LBT issues with the 3.65 >> gear which I believe are related to other AP’s drifting or briefly going >> off timing. >> >> Due to the number of times we were seeing loss of sync we had to enable >> sync + freerun in order to avoid session resets. I’m not convinced that >> we are not still seeing timing jumps due to the sequence of loss of sync, >> into freerun, then an abrupt change in framing when sync comes back. Any >> time something like that happens it tends to cause a wave of DFS and LBT >> events across the network. I can’t necessarily show anything specific at >> this point though. We do get a lot of archived and searchable logging >> from our Sumologic syslog server. I’m going to ask the NOC to put >> together a report of AP’s reporting timing recovery and any correlation >> with DFS or LBT events within a 60 second window and see what we get. >> >> Mark >> >> On Jul 13, 2020, at 3:19 AM, Forrest Christian (List Account) < >> [email protected]> wrote: >> >> I need to be a bit clearer in that I'm not really sure what version this >> customer is running. The question about 15.x /16.x came from a couple of >> oldish threads which indicated that something broke early in 15, and that >> it still wasn't fixed in 16. But I found that unlikely to still be the >> case another year or two on. In these year-and-a-bit old threads, the >> report was that one had to go back to very early in 15.x to "fix" this >> issue. But like I've said before in this paragraph - I find this unlikely >> to still be the case - I just was hoping to verify that this wasn't a >> common knowledge issue that DFS was broken on 16.x. >> >> I know this customer has been in contact with Cambium. Based on our >> conversations with the customer so far, I get the impression that for some >> reason they've decided this is a sync issue. I don't know if this is a >> customer determination or if Cambium has told them this. I like your word >> dubious as I'm skeptical as well, but I'm also not one to dismiss a >> possible cause until I fully rule it out, as they could be 100% correct. >> >> I could see where if you have an AP with sync broken intermittently >> (especially if you have freerun on), you might end up with a DFS event as a >> result of things just not being in sync. But I have reason to believe >> this isn't the case with any of their AP's - at least not the ones I have >> seen the GPS status screen on the RackInjector for. >> >> I could also see where a stray pulse or two may be misinterpreted by the >> AP to be the correct alignment and have the same effect with causing AP to >> transmit out of sync as well. But generally, the radios should ignore >> these as they're very rare (and exist in both the PacketFlux and official >> Cambium gear, so if it's a problem with mine, it should be a problem with >> the official gear as well). >> >> And I agree with you 100% about a dislike for DFS. I have a feeling that >> this customer isn't going to help me change my opinion. >> >> >> On Sun, Jul 12, 2020 at 8:23 PM Ken Hohhof <[email protected]> wrote: >> >>> I am unaware of any correlation between DFS events and either Packetflux >>> or 15.x FW. >>> >>> >>> >>> I don’t use a lot of DFS because honestly it seems fussy no matter >>> what. But I have a tower with 10 sectors in 5 GHz (8 x 450i and 2 x >>> 450m). They are all synced from a Packetflux Rackinjector using Cambium >>> Sync. 4 of the 450i sectors are in 5.4 DFS, and I’m embarrassed to find >>> they are still on 15.2 FW. Uptime of about 6 months and no DFS events. So >>> I’m dubious about all of this. >>> >>> >>> >>> The latest production FW is 16.2.1 and it also has a lot of fixes so I’m >>> not sure why you would be running something so far behind. As I said, I’m >>> embarrassed to find I still have radios on 15.2. >>> >>> >>> >>> Has he opened a case with Cambium support? There are some best >>> practices with DFS. For sure you don’t want to configure the AP to think >>> the antenna gain is lower than it is (not possible with 450m or integrated >>> 450i). You don’t want to set the SM Receive Target Level higher than >>> necessary on other sectors. Then there’s choosing the alternate >>> frequencies. And I suppose a poor sync configuration could cause false DFS >>> detections, where an AP sees the signal from an adjacent AP. >>> >>> >>> >>> But who knows what causes these events? Somebody’s Linksys reflected >>> off a bird? A competitor aiming a new radio? I used to have a 5.4 GHz >>> PTP500 backhaul and the end pointed in the general direction of Chicago >>> would have DFS events when there were storms. I thought ducting was >>> causing it to see distant signals, but it could also have been tripped by >>> lightning. DFS is fussy. I don’t like it. If I could swap out all the >>> SMs on those DFS sectors for 450b, I would probably move them to U-NII-1. >>> >>> >>> >>> >>> >>> *From:* AF <[email protected]> *On Behalf Of *Forrest Christian >>> (List Account) >>> *Sent:* Sunday, July 12, 2020 7:56 PM >>> *To:* AnimalFarm Microwave Users Group <[email protected]> >>> *Subject:* Re: [AFMUG] 450i/450m DFS false detect problem solved in >>> later firmware? >>> >>> >>> >>> I read the 16.0.1 release notes, nothing really specific about DFS other >>> than it being on when it shouldn't be. However, I agree there is lots of >>> stuff fixed in there, some of which could have repercussions for DFS. >>> >>> >>> >>> Are you saying that mid to late 15.x was generally broken for DFS and >>> this is largely fixed in 16.x? I guess my real question should have been >>> 'What is the state of DFS in the 450 platform and how fussy is it'? >>> >>> >>> >>> I'm still gathering information from this customer but it sounds like >>> they're still trying to track down the root cause. Sometime in the past >>> week or so they figured out that there was some correlation between the DFS >>> events adding a fair bit of PacketFlux gear, so this correlation is now the >>> leading root cause in their minds. So now I get to try to resolve their >>> problem for them. >>> >>> >>> >>> >>> >>> >>> >>> On Sun, Jul 12, 2020 at 3:00 PM Dave <[email protected]> wrote: >>> >>> If they are not running 16.0.1 nuthing can help them from some weird >>> issues with the DFS bands. >>> >>> Lots of things corrected in 15.2 and later for EIRP and SNR related >>> calculations the help with H/V misreads and A/B channel alignments. >>> >>> Read the release notes in 16.0.1 for further info. >>> >>> >>> >>> On 7/11/2020 3:12 AM, Forrest Christian (List Account) wrote: >>> >>> I'm working with a customer that is having problems with DFS false hits >>> who is convinced this is a PacketFlux sync issue. I'm never one to say it >>> definitively isn't my problem, but I'm skeptical in this case. >>> >>> >>> >>> I know that at some point in the past that anything beyond 15.0.2 was >>> known to have fairly common DFS issues by some customers. I thought this >>> was resolved in later releases, but I also don't see any mention of said >>> issue being resolved in any release notes post 15.0.02. >>> >>> >>> >>> I was wondering if anyone knew the current status? I.E. if they had >>> been seeing the problem previously, and then discovered it was fixed. Or >>> have tried recent releases and discovered the problem still exists, etc... >>> >>> >>> >>> -- >>> >>> - Forrest >>> >>> >>> >>> -- >>> AF mailing list >>> [email protected] >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >>> >>> >>> >>> -- >>> >>> - Forrest >>> -- >>> AF mailing list >>> [email protected] >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >> >> >> -- >> - Forrest >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > > > -- > - Forrest > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- - Forrest
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