The Signal Booster DUO (Band 12) is made of UNOBTANIUM

John

Your experience is very similar to mine.   Using Field Test on my phone *3001#12345#* I found that I had LTE coverage in my house is between -110 and -120 that changes between Band 2, 4 and 12 depending on the time of day.  4G coverage is usually pretty good.  The Cel-Fi usually locks to a strong Band 2 signal that is listed by the Cel-Fi app as T-mobile 3G CDMA and is always boosted.  Sometimes the booster will lock to a Band 4 LTE signal if that is the strongest one near the Window unit - otherwise it will stay lock to the 3G/4G signal and not boost LTE.  The Band 2 3G/4G signal is always boosted.

I sent the log into Cef-fi and started exchanging emails and yesterday spent over a hour with tech support (Evelin) on the phone (858-485-9442, Option 1). I discovered a few things.  She claimed that the strong Band 2 signal that was being boosted that is labeled as 3G CDMA could actually be a 4G T-Mobile signal.  Also - even though the new unit can boost Band 12, T-Mobile has decided to set the software to not boost B12 signals if there is any B2 or B4 signal available.  So even if B12 is the strongest signal received, the unit is set up to not boost it if a weak B2 or B4 signal is present.  However, the weak B2 or B4 signal may be too weak to be locked on by the booster and will not be boosted so the net result is that no LTE signal is boosted.  Evelin told me that Cel-Fi can send a signal to the Booster to allow the B12 LTE to be boosted but that should be the last resort if you are not getting any other band coverage,  I am fiddling on disabling LTE on my phone at home to get it to lock to 4G and see how that works first or to use Wi-Fi calling as a backup before asking for the software change.  I would suggest that you do the Field Test check to see what Bands are in your home and then give Evelin a call.  She is very patient and helpful.  Looks like you have a similar situation as I have.  Let me know how it works out.

Marty Melnick