The DirecTV SL3K4NR1-03

[Llew]

11506V SIS ident, just missed an OB from Parliament I think.

 

[Llew]

...and a whopping 10.6dB 0n 18552V

 

[scopus]

Llew, can you upload a picture with the 'washer' mod?

 

[Llew]

Hardly a mod, scopus - first thing I picked out from the plumbing spares box! It's probably just the thread of the nut that does the trick. Still, if it works, it works.

Remember this may only be suitable for my Triax dish, but who knows? You'll probably need a meter of some kind to check the exact positioning of whatever you use, I found a mm. out of alignment of my nut, and the signal went down below what it was before I added it.

 

[scopus]

Llew, Amazing what bits and pieces found in the garage will do to help reception. Great stuff!

 

[Vipersan]

...and a whopping 10.6dB 0n 18552V

Pics of the nut addaption please Llew..
Very creative 10 out of 10

Too late ..you already did ..
lol

So rating now ? Norsat V SL3 ?

 

[Llew]

So rating now ? Norsat V SL3 ?

OK, conceded. Got to be the SL3 - plus sundry bits and pieces

Not bad for a 1M dish, might even be OK on the TD88...

 

[Captain Jack]

What's the dish on the floor behind it?

 

[Llew]

What's the dish on the floor behind it?

That's my SMW 1.05 dish, out of action until I find an SMW polar mount (unlikely). Although I often stick it on some bricks for amusement to check the odd satellite.

Original mount, modified, is doing service on the Gibby now.

 

[Captain Jack]

Why not get one of many Channel Master mounts doing rounds on eBay and use that?

 

[Llew]

Often thought about doing that CJ. One day maybe, just need to locate a position in the garden, most of the best places are already taken up by my other poles/stands/greenhouse ;)

 

[scopus]

Interesting arangement and pics ...
I can see why you might have trouble mounting the SL3 but a suitable bracket and mounted in place of the C band PLL might work..
Just keep in mind the weight of the SL3 ..
it is a lot heavier than anything you have on their already ..
rgds
VS

Do my old eyes deceive me or are you growing spikes out of the top rim of the 1.8 ??

Sorry VS, didn't see this bit. Yes, it is growing spikes, the neighbour is a bird friek, so have lots of birds about so the spikes stop them crapping all over the dish

 

[Llew]

I believe that what's happening with my 'washer mod' is that I'm supplying an extra section to the 'missing' part of the feedhorn on these LNB Ka ports - they have half of the outer circular feed entrance cut away so it won't obscure the centre Ku port.
Job to do to make someting more permanent - shape a half-section of some kind to complete the circle, so to speak. Not bothered about obscuring the Ku port, unless I can make it detachable.

 

[Vipersan]

Nice one Llew ..
I'm watching your process with interest ..

btw picked up this before noon today ..
Made me larrf anyway..
prolly nowt to do with the blond buffoon ...but it's a nice thought ..
Him having his own OB and testcard ..
lol

 

[scopus]

I have done a bit of digging about feed horns, and it appears they are available for linear and circular the same as Ku and C band so this could explain why VS after cutting off the septum has problems. Llew you might be right about a missing bit of feed horn. This is from 'Elite' Antennas, that feed would match my Precision dish, but I bet it costs a small fortune

In order to meet the rapidly rising demand for Ka band streams, Elite Antennas now offer our own high performance Ka band feedhorn for use in our Ka band satcom antennas. This is a traditional scalar design coupled to an advanced design of transformer for low VSWR and low insertion loss across the whole band. The feed assembly was developed and verified by Q-par Angus ltd, already famous for a long history of excellence in high end microwave and RF work. The commercial satcomms market can now benefit from performance levels normally reserved for military and aerospace customers.

The Ka band feed is available in single and dual polar variants, and in linear and circular polarisation. It is also compatible with our motorised systems. As well as being supplied with new systems, it is available as a retrofit for many existing reflector antennas.

 

[Llew]

Nice one Llew ..
I'm watching your process with interest ..

btw picked up this before noon today ..
Made me larrf anyway..
prolly nowt to do with the blond buffoon ...but it's a nice thought ..
Him having his own OB and testcard ..
lol

Yeah, no doubt that was for his grand entrance to the toff's boreathon.

 

[Llew]

Llew you might be right about a missing bit of feed horn.

Yes, l'll post any improvements I make as I find them.

 

[Vipersan]

FWIW the septum is an accepted technology absolutely neccessary for seperating RHCP and LHCP in mass produced feed assemblies in Ka since the only other methods open to manufacturers are graduated serations withinn the reed to rotate the signal either Left or Right as in the hughes depolariser OR a dielectric insert ...the latter being less practical at such high frequencies.
The removal of the septum I personally feel is advantageous in order to allow the entire waveguide to pass linear signals ...without rotation.
Of course linear will still pass but is effecticely split either side of the septum thus reducing the signal arriving at each probe by roughly half.
It is a fact that a feed designed to seperate RHCP and LHCP in the path of a linear signal will suffer a reduction by about 3db.
By removing the SL3 septum it then opens up the whole waveguide to a linear signal arriving at one of the selected probes ..in this case Vertical ...untouched and untwisted.
This again is born out in practice as simply removing the septum and making the whole chamber accessible to Vertical ...the Horizontal signal is almost completly removed ..and the vertical signal is increased ..
perhaps not as much as 3db ..but certainly increased,
If you think about it logically it makes sense..
Unmodified both Newsnet feeds and the Teleippica feed both arrive in equal measures at either probe ..
Horizontal and Vertical should not do this ..
The later SL3 has both probes positioned within the signal streams in such a way that is ideal for vertcal linear ..
After modification (septum removal) ....the only way to recapture Horizontal would be to rotate the SL3 through 90 degrees (stand it on its end) ...at which point all vertical signal would be lost in favour of horizontal.
The fact that the SL3 works at all in linear mode unmodified is a bonus ...

not sure what you mean by 'has problems' ..
?
The SL3 works just fine in Vertical only ...
Most days I get over 9db on the OB feeds and 8db -ish on the Newsroom feed.

All that said ..I'm convinced Llew is right about not having complete walls to the feed horn itself ..
My best results to date have been on the older SL3 ..with the feeds cut off and replaced with a septumless concentric feed ..and the SL3 positioned at 45 degrees to the horizontal..


rgds
VS

 

[scopus]

I'll rephrase it, I thought I had read you were struggling with Newsnet after the septum removal?.
You're right about linear, it should not be available on the two probes, which adds the Llews findings that there must be some sort of feedhorn assembly missing, perhaps with some sort de-polariser for the linear?? VS you are much more knowledgable than me on this matter.
I can't wait to have a play as soon as the beast arrives.

Rgds

 

[Vipersan]

I'll rephrase it, I thought I had read you were struggling with Newsnet after the septum removal?.
You're right about linear, it should not be available on the two probes, which adds the Llews findings that there must be some sort of feedhorn assembly missing, perhaps with some sort de-polariser for the linear?? VS you are much more knowledgable than me on this matter.
I can't wait to have a play as soon as the beast arrives.

Rgds

..No probs Scopus..
In a nutshell ..you have described the problem yourself..
No feed with or without depolariser will seperate H and V ..
This can however be done with an Orthomode transformer in the feed line ...but would then require 2x single polarity LNBs attached one to each port output of the OMT.
There isn't a magic feed (sadly) that will seperate H and V that could be placed in line with the signal arriving at one of the SL3 ports ..
These lnbs ..though dual polarity are designed for RHCP and LHCP ...and hence the reason why so much experimentation is neccessary to get the most out of them.
The physical orientation of the 2 probes on each Ka lnb (left and right ports) do not allow for dual linear reception under any circumstances..
Thus ..we have a compromise with both polarities arriving at both probes in unison..reduced by roughly 3db
My removal of the septum on one of these lnb feeds was simply an exercise in maximising the gain on one or both probes in vertical linear ...since the orientation of both probes per lnb is correct for vertical reception only ..unless the modified lnb is physically rotated through 90 degrees that is.
All grist t'het mill ..

..and much fun to be had experimenting..
rgds
VS