Frank Turner-Smith G3VKI wrote in
:

26dB cross-polarisation protection was the "rule of thumb" figure in use
by the BBC service Planning Section in the 1970s when planning TV relay
stations. I know, I was there.
"Active Deflectors", relaying TV signals down into valleys without
changing channels, have been doing exactly what you describe for many
years. For safety's sake, keep the TX and RX aerials as far apart as you
can.


Nice. That looks like bearing out my hopes for the scheme after all. The
distance isn't huge, but I've already decided to aim for the internal
horizontal dipole to be central to the flat, so I can use the smallest boost
that will do the deed.

Small extra question.. Would I get away with a simple low loss coax to dipole
with ferrites on the coax to prevent leaky signals running outside on the
screen, or should the internal dipole get a balun or other appropriate
treatment for a transmitting antenna, despits the tiny signals and extreme
locality involved?