PPCGeeks - Alltel Diamond Question

Ok so i got the alltel htc touch diamond (love it) and over the past few days i have notices something strange. At certain times when i am done with a call or after i exit some menus or after i stop using data, my reception display at the top shows no bars, well after a minute or so it goes back to full bars. If i place a call when it shows no bars it immediately goes back to full bars, i am just wondering what is going on here as i have not been able to find anything about this so far. I dont believe it affects the usage of the phone but its kind of annoying because im not really sure what my reception is.

so if anybody has any suggestions or questions please let me know