Eutelsat 8B, 8W -Weird spectrum analyser traces

[jeallen01]

I have now got vma's s/w running the 138MHz-4GHz Simple S/A connected to the LNB pass-through o/p on my TM5402-3 and am scanning some of the LNBs for the sats that the machine can connect to via the DiSEqC switch.

Most of the spectrums look fairly “normal”, except for those on 8W High Band, where I am consistently seeing something like in the attached screen shots - one is of the full High Band, and the other is from when I narrowed the frequency range

The traces at the lower end of the spectrum are jumping around, second by second, from about +16dB to -40dB of the “average” background levels at those frequencies - there was about an hour between the two screenshots, but I was getting the same thing 2 days ago, and so it's not a short-term occurrence.

So far, I haven’t seen this on any of the other sats I’ve looked at - any thoughts on what those signals are, or, if they are artefacts, then what might be causing them?
(vma suggested corroded connectors, but I don't think that's the reason or I think I would have seen the same thing on the same frequency ranges on from the other LNBs, which have all been installed on a total of 3 dishes this year
My own left-side thought is that this is a sign of a failing LNB on the dish for that sat. OTOH, could it be a sign of a failing transponder, or something else, actually on the satellite?)

Thanks in advance.

John

 

[vma]

Hi,

When I mentioned corroded F-connectors, I was referring to the end that attaches to the LNB. Corrosion can sometimes cause weird effects, like filtering some frequencies.

Other possible causes might include:
- Defective LNB
- Interference (should however be present on the other LNB’s, too)

I am sure that this is not coming from the satellite itself: the noise floor has to be similar than the remaining frequency band, but it isn’t.

Best thing to do is to a) check connector and cable and b) replace LNB.

Regards,
vma

 

[Llew]

Quite normal to see those effects on certain satellites. I see it regularly on my speccy. May be wrong, but I would guess the operator is using some kind of spread spectrum technique of the signal, making it look like it's hopping between some defined frequencies.
Data of some kind I suppose.

 

[jeallen01]

vma - will take a look at that LNB tomorrow and possibly change it

Llew - thanks for that, and you could be right about spread spectrum stuff as it did look a bit like that to me as well.

Cheers all

 

[jeallen01]

Posted some more here

 

[jeallen01]

Morning

It WAS the bloody LNB that was causing the problem - see the thread I linked earlier

 

[Llew]

OK John, glad you solved that, because I don't have any of that occurance on 8W. What I do have is the frequency hopping on 12.5W - I knew it was somewhere around that area of the arc.

Setting my analyser on maximum hold around 12604V to 12625V, the signals jump around rapidly between those frequencies, either side of the Polsat feed presently on 12611V.

The blue areas are when the signals are held at their maximum.

 

[jeallen01]

Llew

Interesting image - wonder what "someone" is actually "doing" with frequency hopping on a commercial services sat (especially in the Ku band)?

Also, from some experience doing EMC emissions measurements with spectrum analysers, I know how extremely useful the peak hold facility can be, but you can't do anything like that with the S/A module & vma's s/w - but then there's at least an order of magnitude (or more) difference in the relative costs!

 

[Llew]

Absolutely, John. That little analyser is brilliant for its cost, and credit to vma for the build. May get the dongle myself for a play.

 

[jeallen01]

Absolutely, John. That little analyser is brilliant for its cost, and credit to vma for the build. May get the dongle myself for a play.

If you do get one, you might need a few other bits if you have not already got them (but you probably do), notably: SMA-F adapters, and a DC blocker (that's the expensive one) if you are running off the LNB loopthrough connector on a sat RX - but it's vma's s/w that makes all the difference!

 

[vma]

Just a quick note: of course you have MAX HOLD function with my software. Just click on the MAX trace (the blue one).

You also have MIN and even AVG (average) trace!

And on top of that, you can use the waterfall diagram, too.

Regards,
vma

 

[jeallen01]

vma

OOPS - many thanks because I never noticed that, and I must look more closely at the various tabs but I will download your latest version before I do that .

 

[vma]

Hi,

I guess that I really need to put some time into a proper user guide...

The TRACE functionality showing MIN, MAX and AVG exists for a long time. Originally it was meant to be as flexible as on most spectrum analysers, where you can define what each trace should show (LIVE, MIN, MAX, AVG, HOLD, CLEAR). I then simplified it, to have less buttons, hence occupying less precious screen space.

Attached is an image showing LIVE, MIN and MAX traces on some Hispasat 30.0W transponders.

Regards,
vma

PS: What device are you using, Llev? That does not look like any field meter I am familiar with.

 

[Llew]

What device are you using, Llev? That does not look like any field meter I am familiar with.

vma, it's a Promax HD Ranger+

 

[vma]

I kind of thought it was a Promax, but wasn't sure. Promax is the one of the few brands (along with Unaohm) I don't have in my field meter collection.
Nice device!

Regards,
vma

 

[vma]

Here is a picture of Hispasat 30.0W with just MIN and MAX traces active.

 

[Llew]

Looking very professional now Vitor, remove 'Simple' from your software's title ;)

Just ordered the device myself to have a play with

 

[jeallen01]

vma

I am sure that many here would be very happy to input their experiences, ideas and comments into your user guide.

BTW, have you yet managed to sort out the Paypal issues (as it can be relatively expensive for anyone outside the Eurozone to transfer small amounts to someone inside the zone) so that we can contribute something for all your time and effort?

 

[vma]

Honestly, I have not looked at it, yet.

While I would appreciate receiving "donations" (no matter how few), which would mainly serve the purpose of purchasing further devices like the 35MHz-4.4GHz version and possibly the NWT4000/NWT6000 models (which support TG - Tracking Generator), I am afraid of fiscal consequences. I need to sort this out, so I don't get into trouble.

Regards,
vma

 

[jeallen01]

vma

Having just downloaded your 2106-11-22 update, I am now having the same activation problem that I had a week ago when I installed the s/w on my other machine and you were kind enough to send me a new code for that machine, because that new code sent a week ago does not work on the newest update (i.e. the activation codes appear to be version-, and not machine-, specific)

PS: to Admins - I think this thread should be (partially?) integrated into vma's thread in the "sat meters and installation equipment" section because it is now far more about the s/w than the problem I appeared to be experiencing on 8W