Switches Simplified

[Anole]

Introduction:

Lots of basic switch questions come up every month.
I'm no expert on the subject, but I've been paying close attention to the people who've been putting them to work.
Some have come up with very complicated switching matrices from the simple building blocks.

So, for a while, I've thought we should roll the basics into one document which might answer many of the more common questions.
This weekend, I ran the idea past Iceberg for his input.
We'll try to keep to 22khz (two kinds), diseqc (two kinds), and multiswitches (two kinds, again).
He suggested we don't get into use of bandstacked LNBs, but they could be the basis of another thread, if needed.

Ku band LNBs:
Before talking about switches, it's necessary to understand the more common kinds of LNBs.
Why? Because some have built in switching, and that interacts with our external switches.

Standard FTA LNBs deal with one band of satellite frequencies, and have one Local Oscillator frequency (LO).
So, no additional switching is built into the LNB.
These regular FSS, or linear, or FTA LNBs have an LO of 10750mhz.

The DBS (direct broadcast satellite) LNBs for pay TV, have an LO of 11250mhz, and work similarly.
However, the term Standard, is used only for the FTA or FSS band, not pay TV.
So, while for most of the following switch ideas, these LNBs can be interchanged, you have to use the right LNB for the job.

Universal FTA LNBs deal with two bands of satellite frequencies, and have two Local Oscillator frequencies (LO).
To select the higher band (the one we use in North America), you must supply a 22khz tone to the LNB. LO=10600
If you don't, the LNB reverts to the lower of the two LO frequencies and low band (which is useful for Europe and Eastern satellites). LO=9750

As we shall see later, the internal 22khz switch of the Universal LNBs sometimes limit their use.

Singles and Duals
LNBs are further divided into single output and dual output models.
The Singles have one connector, and give the receiver Vertical transponders when fed 12 volts, and Horizontal transponders when fed 18 volts.

The Dual LNBs have two connections which operate as above.
For more complicated switching, you can put one output to 12 volts for Vertical and 18 volts for Horizontal, and get both polarities at the same time.
That feature will be exploited in some of the following designs.



See other documents (or our FAQ) if the above is not sufficient, or is confusing.

 

[chapelrun]

Very Nice Document !!!

Thank you, Thank you, Thank you!!! :up

This is very helpful. Switching has alway confused me and this set me straight on several questions.

 

[Anole]

so, you have more than one LNB

The minute you need to move beyond one LNB, a switch becomes a must.
And since we have to start somewhere, we'll first deal with one-receiver configurations.

22khz switch
This is one of the simplest switches.
It lets you choose between two inputs, based on whether or not a 22khz tone is supplied by the receiver, on the LNB power cable.

Since the tone doesn't pass through the switch, you are pretty much limited to single LO LNBs.
And, there is no chance to cascade a diseqc switch beyond the 22khz switch (the signal doesn't get through from the receiver).
I've picked up these switches for $5, at local swap meets.
They have a reputation for reliable switching, as there are only two states of the 22khz tone: on or off.

Ecoda 22khz switch is an improved version, which has the capability to pass the solid or pulsed 22khz tone through to the LNBs.
They sell for about twice as much, but considering you might need only one, the cost difference is trivial.
In a later post, we'll get to what you can do cascading the 22khz switches with other kinds.

DISEqC switch
These come in two- and four-input models.
They rely on a 22khz pulse train from the receiver, to select which input is connected to the output.
Generally, they have only a single output, and are designed for one-receiver layouts.
In a later post, well discuss how they can be used in combination with other switches.

These switches are often considered quite delicate, and can fail if connected to powered equipment.
Prices range from 50¢, to $15... but are often in the $5 range.
This is generally the free switch delivered with a new FTA receiver.

Most models of all switches, do not pass unlimited power.
They'll run other switches and some LNBs, but are probably not suitable for having motors powered from them.
For instance, the Ecoda is rated at 300ma.
Many motors can take that much when under heavy load.


Sample Drawings
Below are two basic examples of the above switches.
While particular brands may be shown, there is nothing special required at this level.

dwg 1: two LNBs, a 22khz switch, and one FTA receiver.

dwg 2: four LNBs, a diseqc switch, and one FTA receiver.

We'll get to more complicated things and other switch types in later installments, but for now, we're focusing on the basics.
These first few posts will be what new visitors read first, so all the more reason they should deal with the simpler switch configs first. -

The drawings are meant to be printed full-page, landscape, on a color printer.
They should have sufficient resolution to be easily read, without being outrageously sized.

 

[jwillis]

Yes, thankyou for posting this, The more I posted about this subject, the more confused I seemed to get.
John

 

[Babadem]

Why can't you use a tone switch with Universal LNBs?

 

[Mr Tony]

Why can't you use a tone switch with Universal LNBs?

Universal LNB's have a 22k swith built in for the low and high band. You can't have 2 22k switches in a row

 

[Wescopc]

Why can't you use a tone switch with Universal LNBs?

When folks talk about a 22Khz (switch or LNB) they are talking about a 22Khz tone.
Bob

 

[linuxman]

Universal LNB's have a 22k swith built in for the low and high band. You can't have 2 22k switches in a row

You can put an Ecoda switch in front of a Universal LNB using the 22Khz on side of the Ecoda switch which will force the Universal to only receive the high side in effect turning it into a standard LNBf with an LO of 10600 instead of 10750.

 

[Anole]

Why can't you use a tone switch with Universal LNBs?

You cannot have two 22khz switches hooked in series.
The Universal LNB has a 22khz switch built in.

Let's take dwg #1 above, and assume the external 22kkhz switch is . . .

Traditional 22khz switch
If you used the traditional 22khz switch, it would not pass the tone through from the receiver to the LNB.
So, each Universal LNB would always stay in the Low Band, and select the lower of the two Local Oscillators.
If you had an application where that was useful, then okay.
But, you could not select the high band nor higher Local Oscillator.
For 99% of the birds visible from North America, that would be useless.

Ecoda 22khz switch
The Ecoda 22khz switches do pass along the solid 22khz or tone bursts.
So, the no-tone switch-input would always be selected when there was no 22khz tone from the receiver
- leaving that Universal LNB in the low band.
Likewise, the 22khz-input would always be selected when there was 22khz tone from the receiver
- placing that Universal LNB in the high band.
Again, if that would be useful, then okay.
However, each LNB would only be selected and left in one mode.

What is hinted at with this arrangement, is that you would be able to put a diseqc switch after an Ecoda 22khz switch, and still get the diseqc to select its inputs.
We can take advantage of this feature in an upcoming sample drawing. . .
. . . once we get to the more advanced configurations.
But first, we'll explore some of the things we can do with what we know so far.

 

[stogie5150]

What, no 3X4 Multiswitch writeup?

BACK TO WORK WITH YA!






( nice job, BTW)

 

[Babadem]

Thanks to Iceberg, Anole, wescopc, and Linuxman.:up

 

[linuxman]

Thanks to Anole!

A much needed thread, and good explanations. I wish it had been here a year ago.

 

[Anole]

LNB drawings

I wish it had been here a year ago.

Took me several years of reading, to figure out the basics. -

What, no 3X4 Multiswitch writeup?

We'll try to keep to 22khz (two kinds), diseqc (two kinds), and multiswitches (two kinds, again).

Patience, grasshopper. -
Assume a new-to-FTA beginner is reading this thread.
What does he need to know first, to get him going?

LNB internals
I found these two drawings, and kept them for future reference.
I'd be happy to give the web page I took them from, but sometimes that info doesn't get saved.

They are block diagrams of the internal workings for Standard and Universal LNBs.
In the Standard, there is only one LO, and the 12/18 volts selects Vertical/Horizontal polarity, respectively.

In the Universal, there are two LOs selected by a 22khz switch that isn't shown, and then 12/18 volts selects Vertical/Horizontal polarity, as above.

edit: added a test drawing of the Universal LNB with the 22khz switch shown.
May have to redraw both the pictures, as they are all difficult to read ...

 

[Anole]

Motor and QPH-031 LNB

Typical Application: Motor & QPH-031 LNB

Okay, so you bought the package system, with all the upgrades:
- motor
- 36" dish
- Invacom QPH-031 linear & circular LNB
- diseqc switch
- well supported blind-scan receiver

Congratulations on a fine selection.


dwg 3: basic motor-switch-LNB hookup

Since the Invacom QPH does linear -and- circular mode on different connectors, the diseqc switch is used to select the desired operation mode.
(unused LNB connectors could be hooked to another receiver)

There are two free diseqc switch ports which could be used for other LNBs.
In this example, the extra LNBs can be Universal or Standard, as there is nothing to interfere with their operation.
Many users have a dedicated dish for G10R (123ºw), so they can change to that bird without waiting for the motor.

 

[Anole]

two switches in series

Eight LNBs and one receiver

This is my dream configuration, for use with a single FTA receiver.
On the left, it has C & Ku band LNB, plus two DBS or Standard LNBs.
They could be any combination of Standard LNBs.

On the right, four more LNBs can be either Universal or Standard!.
edit: well all the LNBs to the right get the 22khz tone.
The Standard LNBs will ignore it.
Universal LNBs would switch to the high band.
If you wanted low band, then you are out of luck.

This all works because the Ecoda 22khz switch passes the tone bursts on to the diseqc switches.
A regular 22khz switch would not work at all , wired this way.

edit: Switch Setting Information

[FONT=Fixedsys] Assume the LNBs are marked from left to right as: 
on the left diseqc switch: A=Cband, B=Ku, D=DBS, E=Standard, 
on the right diseqc switch: E, F, G, H

LNB   diseqc   22khz
----------------------
 A       1       off
 B       2       off
 C       3       off
 D       4       off 
 E       1       on
 F       2       on
 G       3       on  
 H       4       on
[/FONT]

dwg 4: Probably the best bang for the buck, with least connections, and great flexibility for one FTA receiver.

 

[linuxman]

Eight LNBs and one receiver

This is my dream configuration, for use with a single FTA receiver.
On the left, it has C & Ku band LNB, plus two DBS or Standard LNBs.
They could be any combination of Standard LNBs.

On the right, four more LNBs can be either Universal or Standard!.
edit: well all the LNBs to the right get the 22khz tone.
The Standard LNBs will ignore it.
Universal LNBs would switch to the high band.
If you wanted low band, then you are out of luck.

This all works because the Ecoda 22khz switch passes the tone bursts on to the diseqc switches.
A regular 22khz switch would not work at all , wired this way.

dwg 4: Probably the best bang for the buck, with least connections, and great flexibility for one FTA receiver.

This is the precise setup I use with my Twinhan 1020a with 4 universals acting as standards with LO of 10600. It also works with my Coolsat 5K and Traxis 3500. All three of those receivers are diseqc 1.1 compatible with many more possibilities using switches.

The beauty of this setup is that you can also use it with a Pansat 3500, or a Fortec Mercury II which are only diseqc 1.2 compatible and still get 8 LNBs on one receiver.

 

[Mr Tony]

very nice pics But I thought you couldn't do a 22k with a Universal? Does the ecoda work differently for that?

 

[wstef721]

This is a great thread. I have a related question that I can't answer, yet.

I have a 90cm dish with a dual output Universal LNBF pointed at Galaxy 25. I would like to connect up to 4 receivers to this dish. Is this possible? All of the receivers will be emitting the 22khz tone to ask for the high LO. Will they interfere with each other if I use a standard 3x4 multiswitch?

Gregg

 

[Wescopc]

Anole,
I love your drawings, do you do those in Paint? I need to take lessons.
Bob

 

[linuxman]

Hi Iceberg,

very nice pics But I thought you couldn't do a 22k with a Universal? Does the ecoda work differently for that?

On my setup to use the Universals, I have it like this:

Ecoda 22Khz on side then to a separate 4x1 diseqc with the 4 Universals each on a separate port.

In the receiver, I select each port for it's satellite with 22Khz turned on. The Ecoda then sends to the 22Khz on side which passes through the diseqc to each individual LNB using only the 22Khz on high side of the LNB.

I don't know if other 22Khz switches work like that with Universals, but only the Ecoda switch will pass the diseqc commands.