Offset lnb on a PF ??

[Vipersan]

Ok ..after much messing about with the F15 outside ..
The ESX removed from the focus and replaced with the C1PLL ...The best I could achieve lock wise on TPC was 5.3db..
So back in went the ESX and much tweaking later ..back to 7.1db ..
Hmm ..
I couldn't lock TPC with the C1PLL as offset no matter how hard I tried..
Out came the ESX again ..and this was placed as the offset ..
Much tweaking later I finally got a broken lock on TPC at 4.5db..
For all it's glowing reports on various dishes ...mostly offset ..I am now convinced the ESX is outperforming the Titanium both on fringe and tricky channels such as TPC..
The C1PLL wont end up in the (s)crap box as it is still a worthwhile addition to my lnb collection ..
BUT I think I will be investing in a second ESX241 to continue my offset experiments.
More expense ..but that's the hobby ..ya win some ..ya lose some.

Anyone in the UK have one to sell ?
Worth an ask before I spend another £22 in the USA

 

[Costactc]

I have an esx241 single which I put on my 2.4m solid last weekend and signal quality is more stable then the bsc 621 lnbf that it replaced. I use a bsc422 lnbf on my bud, have you ever tried one of those? If your interested I have an extra one which is a dual output.

 

[Vipersan]

I have an esx241 single which I put on my 2.4m solid last weekend and signal quality is more stable then the bsc 621 lnbf that it replaced. I use a bsc422 lnbf on my bud, have you ever tried one of those? If your interested I have an extra one which is a dual output.

Indeed I have one Costa ..
very marginally lower gain than the single BSC421 ,,which was my second lnb bought after the real cheap Pauxis got me hooked on Cband..
I used the BSC421 right up to discovering the ESX..and the BSC422 before I made my switching system more complex.
Which made the 422 redundant..
Each time I have upgraded lnb I got a little more Pauxis > BSC (421-422) > ESX241 ...until the Titanium ..which imo gainwise is much on a par with the 421 ..but oddly comes into it's own on smaller offset dishes..
TBH at the pinnacle of voltage swiched lnbfs remains the ESX imo
rgds
VS

Oh ..forgot to mention the ESX is back in place at Christinas focus ..and some judicious tweaking got me another 0.3 db on TPC..
So today wasn't a total waste...
0.3db might seem little to celebrate ..but if it's on offer..I'll take it
;)

Last point worth noting ..The Titanium placed at exactly the same position at the focus locks TPC around 5.2 db _with_a Concentric ring flat plate ...and this is needed ..to achieve this.
The ESX will lock TPC at 6.1 db without any feed plate ..
Says it all really.....and 7.0 db with the supplied feed plate ..and 7.4 db with my corotor deep feed plate fitted.

 

[Vipersan]

Had a short length of 8mm copper tube left over after constructing the 'Hello Kitty' head ...
So borrowed the extended loop idea from an earlier picture ..
using a cut down concentric PF feed plate ..
Seemed a logical way to mount a second lnb ..and can adjust to suit by bending the 8mm tube easily by hand to get the required look angle..

 

[Vipersan]

Very Very pleased with the results now..
Am locking TPC at 1W 5.9db on the offset ..and this is probably the most troublesome of my 'reference' transponders.
Made some more tweaks to the 'trombone slide' mount ..
Now possible to get much closer to the ESX prime LNB ..though I restrict the proximity to the restriction of a concentric feed at the sweet spot..
As this is needed for DXing ..
Both lnbs are now ESX241 ..and both currently fitted with a Pride Plate..
The offset ESX is fitted with a concentric feed plate ..but this is cut down and thus smaller diameter ..
Also it is fixed and forms part of the trombone slide mount...and about an inch further back than the feed at the focus.
This better suits the Offset ESX as it gives best results when NOT aimed at the dish centre ..but actually a few inches off centre..
Not quite parallel to the prime ESX but very close ..
The pics explain better I think..
Nonetheless just locked Rede uniao at 40W ...at 9.7db (Offset ESX) and 10.5 db (Prime ESX)..
So less than 1db difference now.
I calls this a success..

 

[Captain Jack]

You're doing well - I am only getting 6dB on that TP!

 

[Vipersan]

Time to go open the shop ..but just a final pic to prove Christina returned to 1W with predictable and repeatable results.
rgds
VS

 

[Vipersan]

Still hoping to push for a fraction more from the offset ESX ..
Variation depending on modulation type can be as little as 0.8db ..to 1.7db ..
Typical example is the Startimes mux 5West 5154R 28485-5/6 8PSK
Lockable on the prime ESX (focus) at 10.5db ...but remains unlocked when switched to the offset ESX which only gives 8.8db..
Possibly due to lack of a full sized concentric choke/feed ....more likely the inefficient arrival of signal at the lnbs throat (out of phase slightly and therefore more error prone it being 8psk..
I _will_ max this out given time ..but it can _never_ substitute for being at the sweet spot.
At the risk of repeating myself ...in the words of Highlander 'there can be only one'
rgds
VS

 

[Captain Jack]

That StarTimes mux on 5W is annoying. I never managed to lock it... the most I had from it is about 8.4dB but no lock... what SNR do I need for a lock there?

 

[Vipersan]

Approx 9.5db minimum preferably 10plus for Startimes mux at 5W..
Been doing some tweaking this morning and managed to fit 2 full sized Choke feeds on both LNBs
Because the Offset works better slightly further back ..I can underlap the offset feed ..and still get the prime feed close to optimum ..
Though had to sacrifice a fraction of gain..
Results are comparable..
Startimes mux on Prime LNB = 10.6 this morning and locked solid.
Startimes mux on offset = 9.6 and also locked..
So ..the gap closed to 1db on an 8psk signal..
Don't think I'll get it any better ..so took some photos so I can reproduce this when a more solid fix is done..
rgds
VS

 

[RimaNTSS]

2Vipersan: Is that what it seems ....... I mean, speed camera?

 

[Vipersan]

2Vipersan: Is that what it seems ....... I mean, speed camera?

No mate..
Bog standard IR nightvision camera ..
Enclosure made by me some years ago out of large plastic conduit.

 

[RimaNTSS]

You are making multifeeds on PFA. And that is mostly cuz you do not have place for another BUDs. I just wonder, perhaps if you had something like revolver type LNB changer, so after changing LNBs each one of them will be in exact focus. I've seen such changers and looking forward to design and make one for myself.

 

[Vipersan]

You are making multifeeds on PFA. And that is mostly cuz you do not have place for another BUDs. I just wonder, perhaps if you had something like revolver type LNB changer, so after changing LNBs each one of them will be in exact focus. I've seen such changers and looking forward to design and make one for myself.

I have considered something like this myself Rima..and look forward to seeing any designs you come up with..
Certainly that would be the perfect solution..

@ Rima Do you have any links to such lnb changer devices in use ?

 

[RimaNTSS]

I even do know person who did something like this. BtW, you also know him via this forum. He's made it for Fibo dish. I'we looked in net but could not find such a rotator for PFA, but I am positive, it could be designet. Perhaps it only can become quiet big, so not for small PFAs.

Sent from my HTC Desire 300 using Tapatalk

 

[Captain Jack]

Yes, Trust1 did the rotator for the Fibo. It would be a simpler affair for the PF dish as the mechanism would simply need to slide a few inches back and forth to put the correct LNB into true focus.

 

[Vipersan]

Chances are the relevant info and pics would have been flushed by now...
Perhaps admin still have the thread in a previous backup ?

 

[Trust]

http://www.satellites.co.uk/forums/threads/c-band-on-fibo-120.157748/
Here you find some pictures of my secret wapon .

 

[RimaNTSS]

I was thinking about change-of-the-LNBs issue for PFA. I think it is possible but not so easy. First of all antenna should be big enough (I think 180cm minimum), secondly, it should be on the polar-mount (for Az-El mount task will be much more difficult). Device not necessary should be revolving, could also be linear. So I made small drawing for linear one. Total of the main frame (blue) 80cm. Red frame is movable one holding all LNBs. And green is actuator (do not know what type it should be, but hope they exist and maybe even in smaller sizes).
So, what do you think? Critics are welcome.

 

[Vipersan]

More of less the same idea I had Rima except I would slide the lnbs vertically ....and possibly use a sleeve steel cable such as that use on a bicycle gear change ..
Not sure how exactly this would be achieved but the idea was to get the actuator bulk/weight away from the reflector itself.
The circular chokes/feeds make the job so much more difficult ..imo.
rgds
VS