Finding transmitter engineering information these days doesn't appear easy!
Looking up Crystal Palace at
http://www.digitaluk.co.uk/how_do_i_...ineering_works produces only the vague and unhelpful
TV (analogue) Liable to interruption
https://faq.external.bbc.co.uk/templ...terferencePage wants you to jump through hoops before coming up with:
Transmitter_ Channel_ Effect___ When
Crystal Palace BBC ONE Weak Signal from 08:00 on 27 Jan to 16:30 on 27 Jan
Crystal Palace BBC ONE Weak Signal from 16:30 on 27 Jan to 08:00 on 28 Jan
Crystal Palace BBC ONE Weak Signal from 16:31 on 26 Jan to 09:01 on 27 Jan
Crystal Palace BBC ONE Weak Signal from 08:00 today
Crystal Palace BBC ONE Weak Signal from 05:43 today to 08:00 today
Crystal Palace BBC ONE Off Air; DSO related from 00:30 today to 05:41 today
Crystal Palace BBC ONE Weak Signal from 16:30 yesterday to 00:30 today
Crystal Palace BBC ONE Weak Signal from 08:00 yesterday to 16:30 yesterday
Crystal Palace BBC TWO Weak Signal from 08:00 on 27 Jan to 16:30 on 27 Jan
Crystal Palace BBC TWO Weak Signal from 16:30 on 27 Jan to 08:00 on 28 Jan
Crystal Palace BBC TWO Weak Signal from 16:31 on 26 Jan to 09:01 on 27 Jan
Crystal Palace BBC TWO Weak Signal from 08:00 today to 14:20 today
Crystal Palace BBC TWO Weak Signal from 14:30 today
Crystal Palace BBC TWO Weak Signal from 14:20 today to 14:30 today
Crystal Palace BBC TWO Weak Signal from 16:30 yesterday to 08:00 today
Crystal Palace BBC TWO Weak Signal from 08:00 yesterday to 16:30 yesterday
(Sorry for loss of formatting) which is, at least, informative!