I have noticed during range testing, that my multi-channel receivers lose a huge amount of range test distance as the battery power percentage drops.

I recently experienced these results.

I tested a 6014, a 608 and a 617. Each receiver was plugged into only a freshly charged NiCd battery to power up the receiver. The receiver was set in the same orientation on a flight bench with the RX antennas positioned side view to the TX in a near 90 degree orientation. There was only open field behind the receivers, for around 300 or 400 yards to the treeline to try to prevent any reflection potential. The radio was carried to my side, leaving an unobstructed view to the receivers. The TX antenna was pointed downward with a side on view to the receiver.

With a power level of 56% on the 12Z, I was able to test out to about 90 yards with the 617. Both the 608 and the 6014 dropped out at around 35 yards. On another day, the only difference being the TX battery had been freshly charged and was at 100%, the 617 tested out to 110 yards, the 6014 to 130 yards and the 608 to 109 yards. The purpose of doing this a second time was to test my other 6014, which also tested out to around 120 yards.

Would these results be considered normal?