Advice Needed My Astra 28 H polarized channels gone

[bobbywise]

I watch a lot of BBC News HD. All of a sudden the signal went dead.
After playing around with other Astra 28 channels from the different satellites, I've concluded it's only on the H polarized signals on 28E.

I have 4 LNBs going through a switch which can also pretend to be a motor (I have it configured in Motor mode). I quickly checked Astra 19E which is obviously another LNB, and the channels on H polarization were fine.

Before I start swapping things out, can some people confirm the the H polarized signals on Astra 28 are OK ?

Since Astra 19E was ok, I'm assuming it could be my LNB at 28E that's dying, or possibly the switch.
Having said that, I have one dual LNB on a dedicated 28E bigger dish, and the other LNBs on a smaller dish for 19/13/23E. But the V polarized signals on my 28E dish are perfect, so suspect it's a dying LNB or switch issue.

 

[Lazarus]

Yes, the H Channels as broadcast are fine.

 

[bobbywise]

Thanks for having confirmed.
I have a second cable from the same dual LNB fed down to the garage. I'll connect it to another STB and see if the H polarized signals are fine on that.

Is it common for a certain polarization to stop working on an LNB ?

 

[Terryl]

Check to see that your satellite receiver is switching to +18 volts DC, it is this DC voltage that tells the LNB to switch over to the "H" transponders.

The best way to test this is to use a DVM and a 5 watt 75 ohm resistor, disconnect the receiver from the coax coming down from the LNB/switch, insert one end of the resistor into the LNB connection, then touch the other end to the outside or the LNB connector, the DVM leads connect to the center lead and the outside lead, when you switch between the "V"and "H" transponders the voltage out of the LNB port should also switch.

+13 volts DC (plus or minus a volt) equals the "V" transponders.
+18 volts DC (plus or minus a volt) equals the "H" transponders.

Some old type switches used with multiple LNB's use 2 coaxes, one for the +13 and one for the +18 switching, the LNB will have two outputs, for two LNB's you would have 4 coaxes going to the switch.

If one of these coaxes went bad you would be missing one polarity of tranponders.

 

[bobbywise]

Thanks for the reply.
Unfortunately, I don't have specialist equipment to do this.
I think I can safely deduce that the STB is providing the appropriate voltage to the other LNBs at 19e/13e/23.5e as they are fine with the H polarized signals. So I can pretty much rule out the STB.
I think the issue will be either:
- the LNB (it's a twin LNB - the other connection has an unconnected cable for now going to my garage)
- the cable between the switch and the input 1 of the LNB
- the output of the switch to the 28e assigned LNB

My original post was to check if it wasn't a temporary issue with all the satellites at 28e, and that's been confirmed.

I have a couple of other LNBs spare, so will switch it out.

I'm curious to know if it's common for LNBs to have issues switching between polarizations.

When I power off/on my STB, the H signal on my 28e LNB is available temporarily, but the signal drops immediately.

 

[Analoguesat]

Its quite possible the lnb has failed from your current diagnosis . Swap the connections over for a quick check.

 

[bobbywise]

It's really looking like the Twin LNB at 28E. I connected another STB to the spare cable from the Twin LNB, which doesn't go through the switch, an exactly the same issue. I have a few spare single LNBs, so will switch it out on a dry day (that roof can be slippery when wet!).

 

[bobbywise]

Just a quick update.
Ordered a new quad LNB, which arrived earlier this week.
Had a dry day or two, so went on the roof and swapped out the LNB.
Everything is now fine.
So as suspected, it was the LNB that was faulty !
Thanks to all for your advice and opinions.

 

[Analoguesat]

Ah thats good it was a simple fix. Thanks for letting us know, & a happy Christmas to you & your family.