Help pls... UPC Analog & SKY

Shinobollo

Hi folks
Could really do with some help pls. I've just figured out something I should have worked out months ago and am feeling as thick as fcuk.
I've had UPC analog forever and SKY since they reached our shores. I eventually got a second SKY box but because of the way the house is wired it made sense to locate both SKY boxes in the one room along with the UPC cable feed. (appropriate subscriptions paid)

All this time I've looped the UPC analog signal through my SKY box using the RF Out to send the SKY and UPC signals to another room over one cable using CH28 for one Sky box and CH36 for the other.

Many Months ago I lost the sky signal on CH28 and presumed that the SKY box in question had a faulty RF Out. Not the end of the world as it could still be watched on the TV directly connected by scart.
Then a couple of months ago the same thing happened with the other Sky box - ie it could only be viewed on the TV that was connected by scart and not via coax on ch36 as before. To get over this I bought a LIDL digi-sender yoke which was ok as long as no one ran around and the microwave wasn't being used !

Both boxes were quite old so I initially thought that it was just coincidence. Eventually I bought a second hand replacement SKY decoder cos the digi-sender was acting up regardless of whether I used ch A/B/C or D. However when I connected the new sky box up the only RF channel I could use was 68 (tried 21-69) and this is not suited to long runs of coax. Picture was as grainy as s#ite after a bowl of AllBran !

Decided to disconnect everything from the TV and Sky box bar the satellite feed into the sky decoder and the rf out cable to the tv.
Lo and behold once the UPC Analog loop through had been removed from the decoder, as if by magic I could once again pick up the two Sky boxes on ch28 and 36 on the tv in the other room. Once I reintroduced the UPC cable to the RF in port on the decoder I lost the SKY signal again.
Talk about feeling like a total gob****e.
It had never occurred to me that the UPC signal might be blocking out everything else - particularly as I had "Lost" my 2 sky signals at separate times.

Can someone please tell me why my UPC signal is blocking every channel from 21-67 - assuming that (1) someone has got this far and is still awake (2) I havent completely confused you with my very long winded, very tired and very very frustrated explanation.
Any help at all would be appreciated.
Oh, If only I still had some hair to pull out !!

Antenna

I can't guarantee this will cure the problem, but if you could get an "LTE filter" like this

http://www.tvtrade.ie/4g-lte.html

use the filter on the incoming RF-in of the Sky box.

Then use a UHF channel from 65 to 69 for the RF-out modulator of the Sky box (and retune your TVs for it).

I assume at present, channel 65 to 69 are clear if you disconnect UPC on the RF-in ??