Talk:Water hole (radio)

I don't get it
If OH radicals obsorb in this region - how come Earth atmosphere is transparent at this frequency? Sure, equilibrium H* + HO* <-> H2O is shifted towards right, but still, three should be plenty of HO* radicals in Earth atmosphere. — Preceding unsigned comment added by 24.118.201.68 (talk) 16:54, 5 December 2017 (UTC)

comment
I've always seen the Water Hole defined as 1420 MHz to 1640 MHz, but I don't fully know why the upper bound is that since there doesn't seem to be a notable hydroxyl line at 1640 MHz. The strongest hydroxyl lines are (as far as I know, which is admitedly limited) at 1665 MHz and 1667 MHz. One official-seeming site shows other hydroxyl lines at 1612 MHz and 1720 MHz, but neither seem to explain where the 1640 number originated. One-dimensional Tangent (Talk) 18:23, 27 August 2005 (UTC)

could it be that there is a lot more noise upwards of 1640 and much less below 1640?

Just a thought. I understood that the hole was the relatively quiet space between the noise from water and the noise from a hydroxyl molecule. Maybe only part of the space between those two points is actualy quiet.