Cell Strength goes down while on Wifi

I've noticed that my cell strength goes down while on WiFi (only 1 bar). If I turn off WiFi, my cell signall strength usually goes to 5 bars at first, then will decrease to 3 bars or fluctuate between 3 or 4 bars or sometime full strength, but it seems to mostly stay at 3 bars, although sometimes it wil go as low as 1 or 2 bars. First of all, is it normal for the cell strength to go down while on WiFi? Also, if I'm sitting in one place for a while, is it normal for the cell strength to fluctuate between 1 or 2 bars to 3 bars. I've even noticed it will go to full strength (cell bars) down to 1, 2 or 3 while I'm sitting in the same spot (and not on WiFi) and then go back to 5 bars, then back down again. Why is there such a fluctuation in cell signal strength while sitting in the same spot? Keep in mind, this is while I'm not on WiFi. Usually on Wifi, the cell signal strength decreases, but I noticed that when I turned on WiFi just now, it also fluctuates. While on Wifi, it'll usually stay on 3 or 4 bars, but sometimes goes down to 1 or 2 bars. I've even see it go to all 5 bars (cell reception) while on Wifi, but most of the time it fluctuates between 1 and 3 bars. Does having Wi-Fi calling enabled impact cell signal strength? By the way, the phone I'm using is an LG Harmony 3.