Tips for greater Bluetooth range - using a Parani with a robot

I had high hopes that my 8" antenna would greatly increase the Bluetooth range using the Parani. I was able to get over 140m/459ft with the stubby antenna pointed the direction I was going (under somewhat ideal conditions).?ÿ

With the 8" antenna I got 185m/just over 600ft the other day (didn't need it, just testing the range).?ÿ

Today I had it struggle at less than 100m going up a street with nothing on line, then tried an open field downhill and it barely managed 150m. I had the directional antenna pointed right at me, held the tablet (Panasonic fz-m1 with long range Bluetooth) pointed towards it just to achieve 155m.?ÿ

The Parani works great when I'm close by but at least around here it's nowhere near as good for range as I was expecting. Working by myself it's a huge time waster to have to set a backsight somewhere just to stake out a house.?ÿ

I ordered a cheaper $33 usb Bluetooth adapter to try with the tablet. I don't want to spend another $120 for the Parani one to find out it didn't help at all, like the long antenna. I feel like it helped maybe 10-20% for range. I know the ideal fix is a $2000 radio handle replacement, or a new robot, but it's not my money and I already told the boss this was working okay, because it was getting me by with the stubby antenna. My other alternative is to go back to the terrible Sokkia iX which I told the boss he could trade in on a replacement for a different crew.

I've tried turning Bluetooth and data off on my phone, keeping it in my pocket away from the tablet, putting the tablet in performance mode instead of power save, pointing the antenna directly towards the backsight, the only thing I can't do is rip out the internal cardiac device in my chest (which does have Bluetooth apparently). Any other suggestions from people who have used the Parani for long range. Especially Jim Frame.

Thanks