I built OpenWrt for a MediaTek Linkit Smart 7688 board, first using the MediaTek driver and then using the mt76 driver. I ran the board in WiFi station mode. Using the MediaTek driver, the WiFi range was comparable to what I get on my mobile phone - it worked up to about 20 yards away from the building in which the WiFi router was located. However with the mt76 driver, as soon as I went outside the building, the WiFi connection was lost.

The MediaTek driver version was built following the instructions on the MediaTek website.

The mt76 driver version was built using OpenWrt git master. The menuconfig options used were:

Target system: Ralink RT288x/RT3xxx
Subtarget: MT7688 based boards
Target profile: LinkIt7688

We've been getting similar range problems on another board with an MT7688 chip, using mt76.

Which wifi chip ??

@elektroman
mt7688 IoT SoC uses internal radio, very similar to mt7603/mt7628

So this might be some mt7601 ...
sadly only mt7610u is in mainline kernel, no mt7610e.

Is the error on device of router side.
iw $dev station dump
will help here

no, it's not a 7601/7610, it's a newer chip (7603/7628/7688), mt76 supports 7603, but as it's added not so much time ago it can be buggy

i think it's a calibration data reading/decoding issue, seems like tx power setup is wrong

Yes, I confirm that it's an MT7688 chip.