The DirecTV SL3K4NR1-03

[scopus]

Thanks for that VS. I'm hoping the 1.8 will help with the loss. Have you tried out the Ku side of this LNB at all?

Rgds

 

[Vipersan]

Thanks for that VS. I'm hoping the 1.8 will help with the loss. Have you tried out the Ku side of this LNB at all?

Rgds

..The Ku lnb will occasionally lock a couple of strong transponders at 19.2E ..
but these are linear signals ..and so the lnb loses at least 3db ...in translation ..
ie linear reception on a circular designed lnb.

Then there is the proximity issue ..
ie channel seperation on 19.2 ..
Channels and muxes are close together ..
Not normally a problem in linear ..as the polarities and channels are alternate ..
But if both polarities can be seen and resolved at the same time ..and very little seperation frequency wise ...you get channels fighting for the same space..

Same probs exist in Ka.. but because there are so few channels with much space between ..
resolving both polarities at the same time ..
..not such a big deal..

In Ku ..It works ..but not very well.

Be more use in Russia methinks..
;)


rgds
VS

 

[Vipersan]

Ok ...time for bed I think..
My eyes hurt ..and my hands are sore ..
Made a start on my blanking piece shaped like a violin body ...
cut from flat 1mm thick copper and shaped to fit inside the space and cover the opening to the Ku lnb ..
Stage one complete ...now I have to think about replacing the missing wall sections ..
most likely also in copper as I find it easy to work (relatively) ...and can be soldered.
rgds
VS

 

[scopus]

That looks the business VS.
Chasing my LNB, the tracking says the darn thing hasn't been posted yet!

 

[Vipersan]

Sadly have to abandon this for the moment ..
I have a test piece of 10mm ally just to see how easy it would be to cut a 2 hole bridge for the centre of the lnb ..
not easy but can be done with drills and files..
Problem tho ..

I can't find an 8mm thick ally offcut on ebay ..
So untill I can ..
preferably an 8mm thick bar 30 mm wide approx ...and roughly 100mm long ..
the job grinds to a halt ..
Here are a couple of pics to give you an idea what I'm planning..
rgds
VS

 

[Vipersan]

Sadly have to abandon this for the moment ..
I have a test piece of 10mm ally just to see how easy it would be to cut a 2 hole bridge for the centre of the lnb ..
not easy but can be done with drills and files..
Problem tho ..

I can't find an 8mm thick ally offcut on ebay ..
So untill I can ..
preferably an 8mm thick bar 30 mm wide approx ...and roughly 100mm long ..
the job grinds to a halt ..
Here are a couple of pics to give you an idea what I'm planning..
rgds
VS

Hold the bus ..
A bit pricey imo ..but just found an offcut ..
150mm x 250mm x 8mm Aluminium Plate ...around a tenner delivered.
Back to the task when it arrives.
;)

 

[Vipersan]

..and to give an idea how much variation in signal levels over the day there can be ..
The Newsnet office feed was a solid lock here at 8:0AM this morning..
Showing 9.3db on the F15 ..
Gradually the signal level dropped to its current level ..below lock at noon 6.8db (F15)
I expect it will be back to lock level later..
The Dish has not been moved even a fraction ...so ..
As I've said many times ...this is not an exact science ..and signal levels from Newsnet vary one helluva lot..
rgds
VS

 

[Llew]

Same here VS, no lock, but 18528V is up and locking here OK at present, 6.5dB. Won't grab the video though.

SL3 mod - I've tried several half-rings made out of cut washers and various shaped plumbing nuts etc. They're all pretty much the same size as the missing feedhorn section, but don't show much worthwhile gain.
The best dB increase I can get now is with a brass lampholder screw. Very critical positioning, it needed very careful alignment with the analyser to position it for best signal. Taped on now, but will be permanently attached soon.

 

[Vipersan]

Same here VS, no lock, but 18528V is up and locking here OK at present, 6.5dB. Won't grab the video though.

SL3 mod - I've tried several half-rings made out of cut washers and various shaped plumbing nuts etc. They're all pretty much the same size as the missing feedhorn section, but don't show much worthwhile gain.
The best dB increase I can get now is with a brass lampholder screw. Very critical positioning, it needed very careful alignment with the analyser to position it for best signal. Taped on now, but will be permanently attached soon.

Can't tell from your photo Llew ..but is the brass ring in contact with the existing 2/3 feed ring ..or raised up in front of it acting like a lense ?

 

[Llew]

It's certainly in an odd position, probably some kind of lens effect, yes. Certainly not true to what we would think is correct regarding 'line of sight' from port to dish. And in this position I get at least 2dB extra compared to not using the ring.

Looking into the port, the right hand inner section of the ring is touching the 2/3 feed ring, and the left hand is at least 3mm away from the feed ring. So the brass ring seems to be looking more to the left of the dish, i.e 'skewed' rather than aligned to the port, if you're looking into the face of the dish. The dish is absolutely spot on 19E, so it's not as if the LNB is incorrectly aligned.

Sorry for such a convoluted answer, hope it makes sense.

 

[Vipersan]

It's certainly in an odd position, probably some kind of lens effect, yes. Certainly not true to what we would think is correct regarding 'line of sight' from port to dish.

Looking into the port, the right hand inner section of the ring is touching the 2/3 feed ring, and the left hand is at least 3mm away from the feed ring. So the brass ring seems to be looking more to the left of the dish, i.e 'skewed' rather than aligned to the port, if you're looking into the face of the dish. The dish is absolutely spot on 19E, so it's not as if the LNB is incorrectly aligned.

Sorry for such a convoluted answer, hope it makes sense.

Explanation totally understandable Llew ..
..but as to why it works ..
anyones guess ..
lol

..a quick guess ..
The point at which both rings are in contact ..as opposed to where they are seperated ..
..possibly due to the missing wall section ...
..but I would have thought it would work exactly opposite to the description ....??

Is my picture correct ..?
If so it sort of makes sense ..
If exact opposite ..
Then no it has me baffled..

 

[Llew]

Beats me VS. Certainly placing the ring flush with the feed ring gives no improvement. I suppose I was just lucky that the lamp ring diameter approximates to a feed (scalar ?) ring, however it's positioned.

 

[Vipersan]

Beats me VS. Certainly placing the ring flush with the feed ring gives no improvement. I suppose I was just lucky that the lamp ring diameter approximates to a feed (scalar ?) ring, however it's positioned.

Check the picture I added above ?

 

[Vipersan]

Ok ..
Perhaps my reasoning has totally left me ..
Or maybe I just had a Eureka moment..
Thinking about the SL3 logically ..
It's 3 lnbs in one ..and only the centre (Ku) can be in a direct line with focus ..boom arm ..dish ..and thus satellite ..
The Ka lnbs to the left and right would be lightly angled to the focus ...IF ..they were seperate lnbs in order to line up with the 2 sats to the left and right..
but they are not ...
So being an integrated unit ...perhaps the cut away ring acts to create a false focus ..ie ..a lensing effect to bend the signal slightly ....
..and your adding of the brass ring corrects this false focus ..thus straightening the beam again .. to accomodate the fact that the Ka port is now at the focus ..NOT the Ku port ..
Long thin individual lnbs can be angled ..whereas a flat 3 lnb combo ..not so much ...
This being their way around the problem.

Chances are the dish is also shaped to give a Horizontally spread response to multiple points on the arc..
A combination of shaped dish and shaped lnb giving the desired effect in the USA

what think you Llew..?

 

[Llew]

Just seen your sketch VS. No, my ring's the exact opposite to that - perhaps I didn't make it clearer in my post. The semicircular section of my ring nearest to the Ku port is the one 3mm away from the feed ring.

Yes, I see what you mean by the false focussing of the Ka ports. That could well be the reason I need to skew the ring.

Perhaps it's accentuated by the shape of my Triax dish, maybe not the same with yours.

 

[Llew]

I certainly wouldn't have locked these Newsnet carriers without the ring.

 

[Vipersan]

Just seen your sketch VS. No, my ring's the exact opposite to that - perhaps I didn't make it clearer in my post. The semicircular section of my ring nearest to the Ku port is the one 3mm away from the feed ring.

Yes, I see what you mean by the false focussing of the Ka ports. That could well be the reason I need to skew the ring.

Perhaps it's accentuated by the shape of my Triax dish, maybe not the same with yours.

Indeed it may be dish matching Llew ..but could also be that I use my SL3 as an offset anyway ..so non of the 3 ports at the focus ..
This MAY be advantageous with regards to this - false focus- or exactly the opposite ...
depending on the positioning as an offset lnb(s) to the left ..or the right of focus.

 

[Vipersan]

Well ...it's a start I guess ..
You remember Hubble being fitted with glasses ?
Well this is my attempt on a much less expensive scale ..
Glasses for my SL3..
;)
I took note of the Newsroom feed signal level on the F15 ...prior to fitting ..
8.3db ...then rushed outside and popped on the specs..
Inside again within 5 minutes and the signal had risen to 9.2 db ..
Of course ..nothing is set in stone ..and this could just be fluke ...and no tweaking of the dish as yet ..but I have to say ..promising ..maybe...?
rgds
VS
The protective cap was re-fitted as it looks like rain..but..
.....according to the TBS card ..
db level is fluctuating slightly around 9.5db ..but the BER = zero..
Not seen that in a while..
Guess I'll just monitor for now.

 

[Llew]

So you've fitted copper rings to the 2/3 feed rings VS?

 

[Vipersan]

Not exactly Llew ..
Short extensions about 0.8mm deep cut from 22mm copper pipe and attatched to the copper blanking plate..
Basically just the waveguide tubes extended for now..
No extra walls or rings..other than these.
the 2/3 ring hasn't been touched.
rgds
VS