Saorsat received way off footprint

[Llew]

Is it some freak of Ka reception? Oddly, I'm getting the RTE TP's in East Anglia with my Hughes LNB on a Triax TD88
Or is this supposed to be impossible in my neck of the woods?
I wasn't having much luck with the feedhorn that came with the LNB, so I swapped it with the broken Inverto's Ka feedhorn. A bit of a Heath Robinson lash-up, but it seems to work OK with the polariser and OMT.

Ignore the frequency shown, the Hughes LNB uses a different IF .

 

[Lazarus]

Perhaps the extant weather conditions have created some strange propagation anomalies?

 

[Llew]

Could be. Will check over a period.

 

[timo_w2s]

How odd.

 

[Analoguesat]

Good catch - maybe a switching error and its on the wrong beam?

 

[Captain Jack]

wow! That's some overspill! Keep monitoring...

VS won't be happy...

 

[timo_w2s]

Good catch - maybe a switching error and its on the wrong beam?

I thought that, or they've switched off some of the other interfering beams and Llew is getting a side lobe?

 

[Vipersan]

Indeed I am NOT happy ...
Seriously pleased for you though Llew ..
Now for the inevitable questions..
You are now using a linear lnb to receive circular polarised signals ..so in theory this should reduce any chance of capture ..
but it obviously hasn't..
So ..next question ..
What happens if the OMT is removed and the inverto feed is lashed directly to the hughes lnb ?
Next question ..
What happens in the Hughes feed is connected to the OMT/filter and hughes lnb ?
In other words ..is it the inverto feed making this amazing result possible ?? or is it the hughes lnb outperforming even though it is linear ??
My interested is greatly peaked now ...
Perhaps a side lobe as has been suggested ..
Or maybe you are beyond the reach of the so called jamming beam ...

 

[Vipersan]

..any chance you could post up the whole scan showing the data humps from 19700 to 20200 Llew..?

I also notice you still have the X band filter in line ..
Perhaps this is playing a part ..?
Could you take some lose ups of orientation of this filter relative to the OMT ?
rgds
VS

 

[Llew]

Well VS, I tried the Inverto feed directly on the Hughes LNB, but this gave nothing of any use doing a scan - just a few bumps across the spectrum.

I haven't tried without the polariser, just the OMT yet, a job to do later maybe.

Regarding the linear/circular mismatch, surely the polariser does that job?

It also begs the question, if the jamming doesn't affect my location (Cambridge), why couldn't I receive Saorsat using the pukka inverto LNB before?

A note on the assembly being used - the Inverto feedhorn is only attached using Epoxy resin, so I have to be careful not to play around with it too much; there's some weight hanging on it!

 

[Llew]

..any chance you could post up the whole scan showing the data humps from 19700 to 20200 Llew..?

I also notice you still have the X band filter in line ..
Perhaps this is playing a part ..?
Could you take some lose ups of orientation of this filter relative to the OMT ?
rgds
VS

I'll do some scans tomorrow VS, I daren't leave it on overnight, the whole shebab would probably end up on the concrete floor otherwise.

X band filter? is that the polariser between the feedhorn and OMT? Sorry for my ignorance, you've had one of these units a lot longer than me!

 

[lovelyperson]

Is it some freak of Ka reception? Oddly, I'm getting the RTE TP's in East Anglia with my Hughes LNB on a Triax TD88
Or is this supposed to be impossible in my neck of the woods?
I wasn't having much luck with the feedhorn that came with the LNB, so I swapped it with the broken Inverto's Ka feedhorn. A bit of a Heath Robinson lash-up, but it seems to work OK with the polariser and OMT.

Ignore the frequency shown, the Hughes LNB uses a different IF .

Great pic......thats some LNB ;)

http://www.satellites.co.uk/forums/attachments/hughes-lnb-inverto-feedhorn-jpg.65931/

 

[Vipersan]

Yup ...
It's the long lump that isolates the transmit frequencies somewhere upwards of 30ghz and prevents anything going backward into the lnb I think..

I'll do some scans tomorrow VS, I daren't leave it on overnight, the whole shebab would probably end up on the concrete floor otherwise.

X band filter? is that the polariser between the feedhorn and OMT? Sorry for my ignorance, you've had one of these units a lot longer than me!

 

[Vipersan]

Yup ...
It's the long lump that isolates the transmit frequencies somewhere upwards of 30ghz and prevents anything going backward into the lnb I think..

Great job anyway Llew ..
damned shame my other unit never turned up ..but certainly I shall be experimenting with whole thing if it ever does..

 

[Vipersan]

Last question for tonight Llew ..
What scale settings are you using ?
reversed scale for inverto should produce a signal at the top end ..??
ie 20185
rgds
VS

 

[Llew]

Last question for tonight Llew ..
What scale settings are you using ?
reversed scale for inverto should produce a signal at the top end ..??
ie 20185
rgds
VS

Well that's the odd thing VS, I just used the Ka Band Inverto choice in Crazyscan. I looked at your previous post where you had the scale reversed, which is I think because the LO is lower on a Saorsat LNB (like C-Band LNB's).

Must be how the Hughes LNB converts the band? Too much for me to work out how tonight, I'll have another play with it tomorrow.

Incidentally, when I fixed it to the dish arm, I left it as is, checked with some surprise that it locked on the Promax and quick=stepped back indoors to do the scan. I didn't even do any peaking of the signal, or take into account the weight of the assembly on the arm.

 

[Vipersan]

No probs Llew ..
I need to reassemble mine when I find all the bits ...so some close up pics of fixing and orientation would be most useful..
In your own time buddy..
You've certainly scored big time with this one..

rgds
VS

 

[Llew]

The 'jamming' transponder is now active here, FEC changed from 2/3 (Saorsat) to 1/2. Therefore no RTE reception here.

I can only surmise that, for reasons best known to themselves, last night they used the transponder to downlink RTE to this area on that footprint for some special purpose.

However, after some dish realignment, the signal has now increased by 3dB to over 9dB, which means for me the Inverto feed is far better for me to use on the TD88 than the Hughes oval feed.

VS, I'll give details of the way I mated the Inverto feedhorn to the polariser soon, and the orientation of polariser/OMT.

Meanwhile, here's a shot of the 19.7 to 20.2 scan.

To do: inject a 27MHz signal into the IF up to the Hughes LNB to see if it switches the H/V over. I have a switching circuit to try out.

 

[Captain Jack]

Llew, so you think it was on the French or Scottish beam? Or simply that the jamming signal on these beams was switched off and the Irish footprint actually does reach as far as Cambridge?

 

[Llew]

Who knows, CJ?. Highly unlikely I would guess.