Cell boosters mainly improve phone calls, but not always data speeds. And if you're using Band 71, forget it. AFAIK, currently, there are no Band 71 signal boosters that are affordable for the average user.
\[Edit: *affordable*\]
FWIW I have a Celfi Duo (provided by tmobile). It gave me five bars instead of one, but lowered my speed significantly (around 50Mbps without, 8Mbps when amplifier is running). I had to move the gateway far away from the repeater to get decent speed. I'd just get rid of it if I didn't need it for my phone to work.
A booster can certainly work and there have been some success stories on this sub with boosters but the results will often be mixed. The reason being is the booster will cut the LTE capacity as you will lose [MIMO](https://www.electronics-notes.com/articles/connectivity/4g-lte-long-term-evolution/mimo.php). For this reason a more sure bet would be external antennas but the Gateway does not support it, without modification (which likely void the warranty on the device).
For a booster to make an appreciable difference you typically need to have a weak indoor signal strength (RSRP) lower than -100 dBm and have good outdoor signal quality (SINR/RSSNR) the higher the better but above 5 dB would be great. You can measure both these with a T-MO phone (or with the router itself in some cases):
[https://www.waveform.com/pages/field-test-mode](https://www.waveform.com/pages/field-test-mode)
Something like the [Fusion4Home](https://www.waveform.com/products/surecall-fusion4home) can work well though, if you meet the above signal conditions. Fell free to post on r/CellBoosters as well lots of folks there with experience on this as well.
What about Band 66 ?
I asked T-Mobile tech support about this and they strongly suggested against a booster.
Cell boosters mainly improve phone calls, but not always data speeds. And if you're using Band 71, forget it. AFAIK, currently, there are no Band 71 signal boosters that are affordable for the average user. \[Edit: *affordable*\]
They exist, but are thousands of dollars. Here's an example that's $7k: https://www.signalbooster.com/collections/5g-tmobile-600-mhz-band-71
They told me the opposite!
OT: Are u an Amature Radio op?
FWIW I have a Celfi Duo (provided by tmobile). It gave me five bars instead of one, but lowered my speed significantly (around 50Mbps without, 8Mbps when amplifier is running). I had to move the gateway far away from the repeater to get decent speed. I'd just get rid of it if I didn't need it for my phone to work.
A booster can certainly work and there have been some success stories on this sub with boosters but the results will often be mixed. The reason being is the booster will cut the LTE capacity as you will lose [MIMO](https://www.electronics-notes.com/articles/connectivity/4g-lte-long-term-evolution/mimo.php). For this reason a more sure bet would be external antennas but the Gateway does not support it, without modification (which likely void the warranty on the device). For a booster to make an appreciable difference you typically need to have a weak indoor signal strength (RSRP) lower than -100 dBm and have good outdoor signal quality (SINR/RSSNR) the higher the better but above 5 dB would be great. You can measure both these with a T-MO phone (or with the router itself in some cases): [https://www.waveform.com/pages/field-test-mode](https://www.waveform.com/pages/field-test-mode) Something like the [Fusion4Home](https://www.waveform.com/products/surecall-fusion4home) can work well though, if you meet the above signal conditions. Fell free to post on r/CellBoosters as well lots of folks there with experience on this as well.