This one's puzzling me

[cs91044]

10 days ago I installed a multi lnb setup on one dish with quad lnbs on 13,16,19, and 28 east

Everything works fine except when I am watching JSC Sports +3 on 13 east Sky sports news on a different receiver sky sports news loses its signal the BER increases significantly

before you draw any conclusions none of the receivers are connected in any way both have entirely seperate single feeds in from independant 4x1 diseqc switches

Whats more confusing is its from two different satellites ie: 13 and 28 therefore two different lnb's

Sky sports news comes in on 12148 horizontal and JSC +3 comes in on 11296 horizontal but on two different satellites

There cant be fault with the diseqc switches as the work flwlessly there must be some cross interference with the two lnb's interfering with each other but as far as Im aware lnb's only send back a signal on the frequency the receiver tells them to latch onto but these frequencies are not even close

Can anyone shed any light my only train of thought is to weaken the signal picking up capacity of the 13 east lnb in doing so this may stop the cross interference

Anyone else any ideas?

 

[rolfw]

Are the DiSEqC switches close together?

 

[Channel Hopper]

The IF frequencies down the cable are 2MHz apart (1546/1548).

 

[cs91044]

@ROLFW yes they are cable tied to the same mast post but on opposite sides of the pole so opposite each other on a 2 inch pole

@Channel Hopper I dont follow what do you mean by your post?

 

[Lazarus]

@Channel Hopper I dont follow what do you mean by your post?

He's logged off right now, but what he appears to be getting as is that when Downconverted to the Intermediate Frequency that appears on the cables from the LNBs to the Receivers, those two channels end up on nominally the same IF: So, they are probably mutually interfering with each other.

By extension, if you select another low band Channel on one system and another high band one on the other system similarly separated by 10600 - 9750 = c. 850MHz (give or take a few), you will undoubtedly find the same effect.

Solution: Physical separation of the worst screened elements of the system and/or better screening. Joints, switches (!!) are the least immune areas.

 

[Huevos]

@Channel Hopper I dont follow what do you mean by your post?

The IF (intermediate frequency) is what comes out of the LNB socket and down the coax after the frequency conversion done by the LNB. It is the received frequency, minus the LNB local oscillator frequency.

11296 -  9750 (l.o. in lo band) = 1546 MHz
12148 - 10600 (l.o. in hi band) = 1548 MHz

 

[cs91044]

excellent answers guys I will do some playing around and let you know how i get on - many Thanks

 

[Lazarus]

excellent answers guys I will do some playing around and let you know how i get on - many Thanks

I have a picture in my mind of some strategically placed Cooking Foil by way of experiment .....................

 

[satelliteman]

Might also be worth re-terminating the F's on the DiSEqC switch. After checking all the above, don't discount the switch ie. poor isolation.

 

[Channel Hopper]

I have a picture in my mind of some strategically placed Cooking Foil by way of experiment .....................

Not another tin foil hat test...

 

[Lazarus]

If the cap fits ............