This seems to be more or less no longer true with 4G. Flying in England last year I observed I had 4G 80-90% of the time using my phone mounted on the canopy. With an antenna that's not in carbon bucket I imagine you'll get it all the time.
On Wednesday, February 28, 2018 at 5:42:12 AM UTC+10:30, Kiwi User wrote:
On Tue, 27 Feb 2018 02:59:09 -0800, waremark wrote:

I think you only get a phone signal when you are
uncomfortably low in the UK.

Confirmed: I remember sitting smack over the centre of Huntingdon at
3000ft on a really nice, calm weekday. I was circling by myself in a weak
thermal, so I Hauled out a phone to let a friend hear the vario at work
but got no signal. At all.

Most of England is so flat that there's no need for more than horizontal
RF coverage at or below the top of the cell antenna.


--
Martin | martin at
Gregorie | gregorie dot org