Topband: Grounded half square/half loop detuning

[Petr Ourednik]

Hello folks,

I am sorry to bother all of You but according to discussion about the 
detuning the antennas I have also question.
All the discussion has been made about the detuning the verticals if I
remember.

I am using the big grounded half square (or maybe to say > half loop)
with 
vertical sections 25m/20m and horizontal section 78m. The system is
grounded
with the wire going under surface back to the feed point where I have LC
network to
match on 160/80/40m. (switched remotely by relays)
On both sides I have also radial system. 4x25m on the feed point (25m
vertical) side 
(I know > not so many) and 10x16m on the other side of the antenna.

The nightmare I have with this nice antenna is that I have no space to
put receiving
antenna far away from this loop so my rotary Delta is no more then
10-15m away. In fact in 
the middle of the loop which makes the strange coupling between them and
the performance
of the receiving antenna is completely destroyed. (...I guess)

I tried to detune the TX antenna by switching the relays to another LC
(80/40m when
I operated 160m etc.) with no effect, also I tried to disconnect the
coax from the TX
when I tried to receive on Delta with no effect.

So simply how can I detune this big monster loop or better to say how to
ensure that 
receiving antenna works well and the problem is really with coupling to
TX ant please?

Any feedback or help is appreciated.

73 - Petr, OK1RP