20m HDMI Weird problem

Hi - Hope this is in the right place

I have a gefen 2x2 switch, Sky HD box (UK and HDMI) i run HDMI cable to 2 LCD TV's one 1m away from Gefen and one 20m away in another room.

I have a HDMI extender (cable powered) at the monitor end of the 20m cable.

If I remove the gefen from the circuit and connect to the 20m cable the TV works great. Remove the Extended and i get horizontal sparkles (assume this is poor signal due to cable length) add the extender and it works well and removes these.

If I put the Gefen iand extender in the circuit i get a rolling/poor/green/white noise picture (looks like it can't sync?) powering off everything and powering on in sequence [source] [gefen] [monitor tv] makes no difference note - Sky box gives an error that the display can;t use HDMI call 0807 xxxxx backup cancels ok.

Removing the extender gives a picture but with the original problem (horizontal sparkles oddly only after the samsung (monitor TV) 26" warms up before it's warm it's 100% perfect..!)

if I disconnect the extender (with the Gefen) and reconnect twice everything burst into life perfect picture....

the 20m cable was cheap..... less than £50 - I know.... I know......

So what is at fault? Gefen and extended don't like working together unless the circuit is broken twice - then it's a perfect 720p picture. So it can't be the circuit it must be handshaking............

I just invested £100 in a ceritified 20m cable (to replace the one i have none certified) only because it can't be the other components.

Love to learn what you folks have to comment on what might be at root cause.

Always makes me feel unloved when no one replies to my posts, I felt a bit sad and lonely for a few minutes - that was until I spent 3 hours searching for answers. Not sure I got all of 'em but I learned alot about HDMI in the process.....

So powering on from source to monitors in sequence helped. As did removing those crappy 90 degree HDMI adaptors from the wall plates. Use them at your peril.

I can get and maintain a picture as long as I don't loose power to the Gefen switch in which case i need to go through the power up sequence again and flick the genfen from input 1 to 2 and back to 1.

I do need to use a booster (self powered) just to remove some noise (looks like scan line interference)

I am a happy bunny and will be offering on eBay the new certified 1.3b 40 foot flat HDMI I just ordered (for £140) from the US for less to replace the 40ft cable I paid £40 for now confirmed to work ok.

So not sure if you're supposed to post answers to your own questions but to everyone out there like me - invest 2-3 hrs before posting

OK as a follow up the 20m flat atlona hdmi arrived with a 1080i rating. I ran the cable including 2 wall plates and the darn 90 degree angle adaptor and guess what - perfect picture (kinda read on) and now I can turn on the LCD with a perfect handshake. All is as I'd expect.

There is a slight scan line drop out every minute or so that I could just live with (lcd is in the kitchen)

Proves the point get the best cables you can afford for longer lengths. I'm keeping the flatty and ditching the cheap round cable.