Problem with high frequencies

B

Burnham Beech

Specialist Contributor
This one has me completely beat - over to you.

I have just connected a new VU+ Duo2 receiver to my existing 1.2m satellite dish and I can't get any transponders over 12515 GHz. Up to 12515 GHz everything is working normally, after 12515 GHz I get 0% strength 0% quality and 0 dB. I have checked many different frequencies on different satellites and the result is always the same - if over 12515 GHz I get 0%-0%-0.

This is where the mystery deepens. If I connect my 80cm motorised dish to the Duo2 - I get all channels over 12515 GHz on any satellite I can receive. If I connect my minidish to the Duo2 - I get all the 28°e channels over 12515 GHz.

And to deepen the mystery further. If I connect my main 1.2m dish to my old VU+ Duo receiver everything is working as it should - including all channels over 12515 GHz.

Would welcome any help and suggestions. More things I could check?
 
I can only think of some sort of incompatibility between the new Duo and the LNB on your 1.2 ... try and change the LNB settings and see if that works , if not try another LNB .
 
Do the other dishes uses the same cabling? Long shot, but maybe the shielding has deteriorated to the point where it doesn't work so well with higher frequencies.
 
I experienced this effect a couple of years ago and discovered that a certain LNB (Can't recall which one) was incompatible with my Foxsat at the top of Ku Band.

Swopped the LNBs around a bit and all receivers and dishes were happy.

I've read of this phenomenon a few times yet can't figure out the science behind it.
 
The single DVB-S2 tuner in the Ultimo/Duo2 is a bit lazy (compared to the Duo) above 12500 MHz. Possibly the LO in the LNB is a bit off frequency. If you couple the two things it might be the reason for no reception. In satfinder try selecting a frequency 5 MHz above and below the one you are searching and this will confirm if the LO is off. Also try doing a blindscan (12500 - 12750 MHz) to see if it find any of the transponders you are missing.
 
Thanks for all the replies so far. I have tried +5/-5 Mhz and got nothing. Tried blind scan over 12515GHz and got nothing.

The LNB on the 1.2m dish is not an IBU (Inverto Black Ultra). It is C120 Inverto coupled with the correct Channel Master feedhorn which I set up six years ago - all giving good service up to now.

The cabling is quite old and may have deteriorated. But that does not explain why the old Duo has no problem with these high frequencies - using exactly the same cabling, dish & LNB - but that the brand new Duo2 does have a problem.

New LNB has been ordered (coincidentally an IBU!), will test and report when it arrives.
 
New Inverto Black Ultra LNB arrived and installed. Signal slightly better than the old C120 LNB arrangement - but still nothing above 12515 GHz.

Next thing to check is the cable from dish to receiver - will test a completely different cable and report on that tomorrow.
 
BB, is it single or dual tuner card?

And where it is working on the 80cm dish have you compared the SNR compared to the Duo1?
 
The 1.2m dish may be collecting signals off beam that the new receiver cannot handle, but this is less likely (and less easy to check) than sticking an attenuator inline to verify if it is simply too much signal at the tuner front end.
 
Latest update - problem isolated.

I have now tried a (temporary) direct cable from Duo2 to the dish - and everything is working correctly. The fault is clearly in the permanent cabling. Four metres of the permanent cable is underground (no kidding - it goes under the lawn) and I think - but I can't remember for sure - that I put a connection in the cable (protected with self amalgamating tape).

The conclusion is that the permanent cable is not working to 100% efficiency, and that affects the VU+Duo2 with its plug in tuner. Surprisingly my old VU+ Duo is not adversely affected by the less than 100% efficient cabling - the VU+ Duo has a non-plug in, permanent tuner.

Thanks to everyone for the help & ideas.
 
Burnham Beech said:
Latest update - problem isolated.

Four metres of the permanent cable is underground (no kidding - it goes under the lawn) and I think - but I can't remember for sure - that I put a connection in the cable (protected with self amalgamating tape).
Click to expand...

Almost certainly water in the cable in that case....
 
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