>The BBC station was indeed decommissioned at the end of the cold war but 1 antennae still remains on the original site on Daventry Borough Hill for commercial broadcasting in addition to the Dodford mast a few miles away.<
I don't think that's one of the original HF array masts, however. From memory, that one belongs to NTL or Merlin.
> How high would DTY need to be and what type of structure would indicate it was VOR Doppler equipped?<
The antenna of a Doppler VOR is a large structure about 30m in diameter and several metres high. Typically there is a large 'ground plane' with 36 radiating elements -- often brick-red or orange -- above it. There are some nice pictures and a good description of how they work at
http://www.trevord.com/navaids. In respect of DTY, the site says:
" The DTY VOR is just North of the Village of Maidford in Northamptonshire - approximately 7 miles SE of Daventry itself. The beacon is in a field and can be easily accessed via a public footpath. You'll need to follow some windy country roads to get to it!
Doppler VORs are somewhat less sensitive to siting considerations than conventional VORs, which is why they're almost universally used nowadays.