DishPro LNB/switch signalling?


Original poster
May 11, 2004
I work for a silicon company developing software for satellite ICs and use free-to-air signals from Dish Network's 119 satellite as a great test input. Using an old, simple 11.25GHz LNB and 13/18V and 22KHz signalling, all is fine. Unfortunately, the new system installed at my home uses DishPro LNBs and SW34 and I have absolutely no idea of the details needed to allow me to select the required signal now. Can anyone tell me what the frequency offsets of the left and right polarized signals are using the new LNB and, if possible, what signalling is required to select the satellite position? I presume some DiSeqC signalling is required.

I'm only wired for 110 and 119 since the guy who did the install took 3 attempts to put up the second dish pointing at 61.5 and then decided it was not possible given the position of our house without slapping it right above the front door - a position that was quickly vetoed by my better half.

Thanks in advance for any information.

Dave Wilson
I figured this was probably the case but also figured that some industrious soul out there would have slapped a scope across their receiver's satellite input to see what it was doing. I guess I'll have to do this after all unless someone else can fill me in on at least enough information to get to any of the 119 bird's transponders containing FTA content. Even if I can't do the full switching protocol, I could survive knowing what the "default" state of the line is if I turn 22KHz off and I drive, say, 13V. There's FTA content on both polarizations but, since DishPro supposedly stacks the frequencies on the cable, all I should really need is the frequency offsets used for each polarization.


Dave Wilson
Unless you have more than two receivers just replace the DISH PRO LNBF with Legacy equipment and you will be back where you are familiar.
Great information - thanks


This is very helpful. In other words, it looks like a dual LNB where the odd frequencies are offset 11.25GHz and the evens are offset 10.75GHz. I'm going to run a scan-the-sky on my line to see what it finds but, with this information, I should be able to hack together some LNB control software that will do the trick.

I'll read the DiSeQC PDF tomorrow once I get back to broadband land. Assuming E* stick with the spec for their signalling, I assume this will give me some idea of how to select between 110 and 119.


Dave Wilson
Investigation results

OK, here's the skinny on the basic DishPro LNB as far as I can tell from scanning what's on the cable and looking at the PATs in the various transponders. I have not yet looked into DiSEqC signalling to select which dish/satellite's signals appear on the cable but, using my DishPro SW34, the signals from 119 appear on the output without me having to do any signalling at all. I don't know if this is the way it always works or if this is just the way my switch "floats" but I can use these transponders for now.
Apologies if my terminology below is off - I'm no RF expert!

Right polarised transponders (odd numbers):
Tuning frequency (IF) = transponder frequency - 11.25GHz.

These transponders sit on the cable exactly the way they did with the old-style LNBs.

Left polarised transponders (even numbers):
Tuning frequency (IF) = 14.35GHz - transponder frequency or
Tuning frequency (IF) = abs(transponder frequency - 14.35GHz)

These transponders are stacked above the right polarised ones and the order is inverted WRT the original transmission frequency. This doesn't cause too many problems since the calculation is just as if you were using an LNB offset of 14.35GHz and subtracting this from the transponder frequency (on the basis that a negative frequency is equivalent to the positive version with a 180 degree phase shift (I think)).

As far as I can see 13/18V and steady 22KHz on/off make no difference at all now. I gather that the LNB needs a 19V supply and I reckon mine is getting power from the other 2 receivers attached to the switch.

I hope others find this information useful. I make absolutely no promises about its accuracy since it is based solely on experimentation on one installation!


Dave Wilson
You refer to your switch as a "SW34" while you're using DishPro LNB. Unh. If it's really a SW34 and not a DP34, unh, might that be the switching issue? Unh.
Sure, he's using DP34.
Dave, I saw reports the DPxx using DiSEqC 1.0 or 1.1. Could you run Switch test on regular Dish receiver and capture all the commands in coax ?
True enough - it's a DP34. I don't admit to being a switch expert - sorry. Unfortunately, I have no (easy) way to sniff DiSEqC on an old receiver but, given that I have the spec, when I get some free time, I'll play with some commands and see what happens - I have also heard rumours that the switch uses standard DiSEqC.
Given that I have now found my 119 signals, though, the experimentation to determine how to select 110 is far lower priority and I probably won't get to it for a few months. If I find anything, though, I will post the results.


Dave Wilson
One of the nice things to find if you figure it all out is a Ku FSS LNB that is compatible with DishPro. Some have suggested an Eagle Aspen would work, but no one has reported that it has tested successfully.
Since DPxx switch is responsible for select right satellite by commands from a receiver, the Ku FSS LNBF should do only one thing to be DishPro compatible - bandstacking, ie NOT required 13/18 VDC or 22 kHz for switching polarity, provide _full_ spectrum from particular satellite. Still questioned is it the FSS bandstacking linear, I mean doesn't have a gap between 'V' and 'H' IF, as DSS bandstacking LNBF doing.
Is someone using Superdish could connect spectrum analyzer for a feed from Ku LNBF ?

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