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Desense on AO40

Hi all, I need some advice.
 My AO40 setup is as follows :
 FT847 435 up 50W
11 ELE end mounted Yagi for 70cm uplink
G3RUH patch feed and 60cm prime focus dish
DB6NT 2.4 GHz downconverter
2 runs of RG213 coax 25M long
G5500 AZI/ELE rotator with fibreglass cross boom 2m long

Problem is I have just taken a 19 ele crossed yagi 70 cm beam (center
mounted) off and replaced it with a  smaller 70cm end mounted 11ele
beam. When I transmit up to AO40 I get desense on the 2M IF receive
signal. Do I fit a N type T piece between the DB6NT downconverter and
the coax feed and use a open ended stub cut to notch 70cm ?

I presume this problem is because the driven element of the 70cm beam is
now closer to the dish feed compared to the larger crossed yagi which
had its driven elements several feet behind the dish. You may ask why go
for a smaller antenna ?
Its simply I have little space and my neighbour in the upstairs flat has
to look out on this array. I know I can get into AO40 with the smaller
antenna if it wasn't for the desense.

Any advice would be appreciated.

73s Darren G4VTQ

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