A couple more db.

[$ly]

Twin O/P LNB two feeders of the same length, an F 'T' piece and phase compensation by screwing one of the F connectors on a millimetre at a time and removing the excess as required to peak the sig.

Anyone have any serious problems with this ??

Discuss


L.

[BGonaSTICK]

Maybe :?

Are you just chewing the fat, or are you going to try it?

It's entirely possible, but I don't know what 'real-world' obstacles you might face.

Seeing as this is not an everyday thing, I'll risk looking a tw@t and just say stuff that comes into my head.

Maybe the actual length of the two tails would have an effect? I agree that tuning the lengths to match each other sounds a sensible way of matching the phase of the signals, but would the length itself have an effect? Would the 'T' joint cause some sort of reflection, setting up it's own standing wave? Would this be any different to a single feed, or cause any complexity?

And there's more...

Does a twin LNB use the same LO to reference both sides of the LNB? If it did (and I think that sounds likely) then this would surely be a better way of approaching a dual-feed setup than having two single LNBs and/or two dishes. If it had two LOs would they be in phase to start with?

Then there's...

Would there be an issue caused by effectively shorting the screen between the two LNBs? My Invacom twin is weird. One output has the signal and screen isolated, whilst the other side displays continuity. I have effectively shorted the two screens on mine by having two receivers connected - both on a floating earth, but here the two would have a common earthing point - the receiver chassis.

And what about...

...the receivers ability to power both LNBs at the same time? Could it do it? Would it do it? Would it put an undue strain on the STB? Would the correct voltages be maintained to switch the LNBs correctly? If it was a problem, you could always introduce a secondary power supply I suppose, switched by the receiver? :?

I don't think any of it would be a problem personally, but then I don't have a clue what I'm talking about! :roflmao:

I do know that it's possible to aggregate IF signals at Ku band in this way (or at least in a similar way), but I can't for the life of me remember where I read it. It wasn't a home DIY job, that's for sure.

Let us have the results as soon as you get them

[Analoguesat]

It would be much less hassle just to put a bigger dish up!

Give it a try (not with your best receiver as Im with Stick on this one - you stand a chance of overdriving the power supply unit.... and fluctuating voltages could play havoc with your experiment.)
Try it and see - then let us know!

[Stv]

Surely this would be like the argument against signal boosters - you won't be any better off because you'd still have the original noise, just louder.

Both LNB connections would be trying to output the same voltage, so I guess your only boost would be in the current, which as BGonaSTICK said would depend upon the receiver being able to feed two LNBs suitably at once.

I'm pretty sure you would control phase through using a resistor with an inductor/capacitor. Either way, that would introduce a power drop with respect to the other, so would lead to further problems. I haven't a clue about changing the cable length but I suspect the difference would be minimal. Then there is getting the modulated content in phase, as well as its carrier wave. That would leave the LNB inputs fighting each other producing what I guess would count as even more noise.

Just to add to BG's rambling :P I'm not sure how much of it is correct

[$ly]

Good, generated some thought there then .
Thinking of it as being two separate dishes for a moment then the only problem I see is the phase difference, and the only way to effecitvley get this right is feeder length as I see it and the two LNB's are going to be as matched as you could realistically hope for

The current thing shoudn't be an issue as I'm sure there is some slack in the PSU as they can drive DiseQC motors.

The floating earth thing, going to use an Inverto twin C120 which I believe has a cast metal body.

Got an okd Broadlogic PCI card kicking around as the test rig (don't want to hurt the old SS1)


Going to give it a whirl in a week or two as theoretically 3db is on offer but even two thirds of that would be like having an OP150 as opposed to the OP120 I have now so the signal increase would be more then marginal.


L.

[BGonaSTICK]

Sounds more and more like an interesting and worthwhile project with every new post!

Going back to Stv's point, it's not really like the signal booster analogy IMO, because there you're simply amplifying what you have collected (at which point the majority of the noise is already present), whereas this is actually (and independently) collecting more of the original microwave signal - just like having a dish face which is twice the size.

I do think though that it would be all to easy to generate a deafening amount of noise by not having the signal phasing exactly correct, and I have no idea whether you would need to do this by tuning patch-lead lengths or introducing resistors/inductors/capacitors etc. I think that if you can sync. the carriers, then the rest will take care of itself :?

I also think the power supply thing will be OK, as the LNBs surely don't draw much current.

I await the photos of the singed eyebrows, scorched PSU and melted coax with interest though :clap: :spite:

[$ly]

Update, just found a female 'F' tee piece on fleabay for £2.50 so we're all go in a couple of days.
Couldn.t find one of these easily anywhere up till now.



L.

[Analoguesat]

Ive got loads of them in a draw at work L!

Ive got this theory they migrate through tiny T-shaped wormholes in the fabric of reality and end up in in my storeroom!

[BGonaSTICK]

Yours is somewhat of a special case, but I actually posted about this very same item the other day

http://www.satellitehelp.co.uk/forum...ic,5456.0.html

[$ly]

I guess I'll be using it backwards to the way they are advertising it, but as you rightly say it'll be virtually no use otherwise.

@ AS, typical. Didn't even consider asking any network guys

Anyway, ordered it at 2pm and just turned up with the morning post


L.