For info re signals, this (commercial) site is worth a look: How to Boost Cell Phone Signal at Home For Free
About registering the booster with the carrier: Register Cell Phone Signal Booster
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The booster I think is just basically a repeater, it will repeat whatever signal it gets, itās a dumb device in that respect, otherwise youād have to get a SIM for it and you donāt need a SIM as far as I know. So saying that it is still interesting to me that youāre having these phantom signals your phone is trying to connect to because really the SIM in your phone should only associate with those carriers that the SIM is registered on.
Not that Iām glad youāre having this problem but it makes me think that there is something more going on here with these Broadmobi modems and the firmware weāre using perhaps. I think itās definitely worthwhile talking to support because the more intel they can get about this the quicker it gets resolved. Are you with AT&T by any chance or one of their affiliates?
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I am not with AT&T just Mint.
Yes, the problem is the modem does not stay with the SIM for Mint Mobile. It bounces around. On what basis? Not sure.
I also tried registering the booster with T Mobile for what that is worth.
I am also contacting support and I will report back.
In my case when Iām at work in town it seems to like the tower Iām connected to but as I travel home (I too live in a rural area) it becomes very flakey and behaves just like what youāre saying. Itās very hit and miss and when I get home it fails to register at all. The same SIM works flawlessly on my android phone. I really think there is an issue with the firmware, the modem or both. I really hope they can find a better modem at some point.
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I wonder if they could get this bad boy working in our phones?
I am wondering if I can make the modem only recognize certain frequencies as possibly suggested here:How to use 4G LTE modems like the MC7455 on both Debian/Ubuntu and OpenWRT using MBIM Ā· GitHub
It makes me think there is some sort of issue between the modem and the SIM, it should be ignoring any frequencies that itās not getting registration messages from. I donāt really know for sure but thatās my thoughts.
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That is the response with a hopeful solution, I would like to get back from support.
Just putting it out there but it is possible that the repeater is repeating on a different frequency i.e. receive original signal on one frequency and retransmit on a different frequency - with the intention that your phone registers on the latter, which will be much stronger, but logically your phone could register on the original.
This kind of device is used extensively in my country but I donāt have one so I am just speculating.
In some cases people may be using non-compliant repeaters that may stuff things up for other phone network users.
Also bear in mind that, for emergency calling purposes, a phone must be able to āregisterā on networks that it is not authorised to register on. The SIM authenticates the subscriber but it is not the be all and end all.
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I understand the gist of what you are saying but my experience with cellular at home has been pretty brutal. My wife and children both have cellular at home with their Iphone and Android devices. Me? I get nothin. I find that unacceptable and do not give up easily.
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Are your family members on Mint, too?
Yes, my son is.
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No I get that, a phone without a SIM should be able to make a 911 call but Iām not about to start doing 911 calls to test the Librem 5 
My phone is headed back to the mother ship for more analysis so Iām hoping they find something, otherwise I think I might be dead in the water until a new/different modem can be used.
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Yes, I agree.
My point was: the SIM must not constrain the networks that you can register on.
The applies when there is no SIM but it also applies when there is a SIM if the network operator relating to that SIM is āmalfunctioningā. It could even apply if there is a SIM and the network operator relating to that SIM is working fine if the SIM is not unlocked. In all of those scenarios, you must be able to make an emergency call - and that means (potentially) completely ignoring the SIM and grabbing any network that works.
Whether this has anything to do with your specific problem I donāt know. It was more just to point out that there is complexity involved and hence just ignoring the networks (frequencies) that you shouldnāt normally be on may not be acceptable.
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I completely accept what you are saying. However, I am having a hard time understanding why a modem in an Iphone or Android can differentiate between the TMobile signal at my house and ālockā to the SIM, thereby using only that signal. Conversely, my modem, the BM818, cannot or will not lock into a particular signal but bounces around looking for, I believe, only the strongest signal.
Can I not just force the modem to lock on the signal of my choice at my house, somehow? If not, why not?
You can call the non emergency number and request to do a 911 test on your hardware. They will let you know if you can or canāt. Iāve heard that if the lines arent busy they will usually say yes.
Quick question, when you go into mobile settings can you manually select the network you want to connect to? Iām asking because when I try that on my phone it just times out and gives an error. I think there might be a clue there.
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Hello. I appreciate you caring about this post with me 
Yes, I can select āMintā but I cannot force it to stay there! There is a āsetā button and when I push āsetā, I get this message:
GDBus:Error.org.freedesktop.ModemManager1.Error.Core.WrongState: CannotRegisterModem: modem is connected
FWIW, I am emailing with support but that is going very slow and not much help so far. I was not expecting much but I am being pushy and sometimes pushy works.
Interesting, I donāt even get a list of networks to connect to but that is the error message I get as well.
Short answer: different hardware + different software/firmware = different performance
Question: When you notice the phantom signal, does āMintā disappear from the Mobile settings in the Settings app?
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