DiSEqC switching between fixed and motorised

[Captain Jack]

Hi all,

Been setting up the dish today at the bottom of the garden and despite moving it as far back as I can, I cannot receive anything further east of 23.5 due to the house being in the way. The dish is set up *very* roughly, the pole isn't 100% vertical and most bolts are tightened up by hand only.

That said, unless I lift the dish up higher, which I don't want to do as it will then be visible above the fence, I don't think I will get 28.2 on this dish. However, I do have a "mini dish" on the front of the house receiving Sky TV, so I wondered whether it's possible to connect one of the LNB outputs to a bog standard DiSEqC switch and use my Dreambox 800 to switch between that and the motor automatically? I have a Global Communications 2-way switch from ages ago when I had Astra/Hotbird dual feed - can I use this?

So, the diagram would look something like this:

USALs motor ---------DiSEqC switch----------DM800
|
Sky dish------------------
|
-----------------------------------------Sky Digibox

Also, before I moved, I noticed that signal on the motorised dish tended to "jump" a little. On the Dreambox, this was showing as a 3% or 0.5dB SNR difference. I replaced the tuner in the Dreambox with a new one and also replaced all the cabling from the LNB to the receiver but it's still the same. Does it sound like the LNB is on its way out? The LNB is a Technomate 0.1dB - are these any good? Should I just replace it with a Black Ultra? These seem highly regarded....

Thanks all!

Alex

 

[Huevos]

Not sure about the switch, but if it is DiSEqC 1.0 or 2.0 you can use it. The chain will be receiver -> DiSEqC switch -> USALS motor -> LNB.

Put the Sky dish to input 1 of the switch and the USALS motor to input 2.

Tuner config is "Advanced".

Config as follows:

28E:
LNB 1
DiSEqC mode: 1.0
Committed DiSEqC command: AA

All other satellites:
LNB 2
DiSEqC mode: 1.2
Committed DiSEqC command: AB
Use usals for this sat: yes

And fill in your correct co-ordinates.

When going through all the other satellites once LNB 2 is configured you just switch each subsequent satellite to LNB 2 and all the settings are already done.

 

[Captain Jack]

Thanks Huevos! Definitely a 1.0 switch, so it should be OK (hope it still works!)

Will I have to go through every satellite I receive for LNB2 or is there a "default" setting?

 

[Huevos]

Thanks Huevos! Definitely a 1.0 switch, so it should be OK (hope it still works!)

Will I have to go through every satellite I receive for LNB2 or is there a "default" setting?

you have to go through them all and select lnb2.

 

[Terryl]

Its better to put the motor before any switch, less voltage loss to the motor and the less current running through the switch.

It should go receiver directly to the motor then any switch then the LNB.

Also good coax with a pure copper center conductor will have less voltage loss the the cheap copper plated stuff.

 

[Huevos]

Its better to put the motor before any switch, less voltage loss to the motor and the less current running through the switch.

It should go receiver directly to the motor then any switch then the LNB.

The motor only draws 250mA, and if you wire it as you suggest it would not be possible to have 2 USALS motors on one tuner if he ever wanted to at a later stage. In this case where Captain Jack can see the arc from 57E? to 28E at the front of the house, and 23E to 30W at the back. The only way to cover the whole arc with one tuner (DM800) would be a DiSEqC switch and 2 USALS motors, which if you put the switch after the USALS motor would not possible. Also it means the cable for the 28E dish needs to go to the back of the house before going to the front meaning an unnecessarily long cable run.

Personally, on the second tuner of my Vu+ Duo I have the very setup I recommended in post #2 (1.8m fixed dish for 28E and motorised for all other satellites with a switch in line before the USALS motor) and it doesn't suffer any voltage drop across the switch.

 

[Captain Jack]

Brilliant - thanks!

Any ideas on my issue with signal fluctuations? Anyone know how that Technomate LNB compares to Black Ultra?

 

[Terryl]

2 motors would put the average FTA receiver over budget in the current draw on the power supply, unless the recivers you all use over there are different then here on this side of the pond.

And basic engineering 101, anything inserted into the system that is passive (not run by an external power supply independent from the supply from the receiver) will have both insertion loss in the over all RF signal and DC voltage loss due to it's internal DC resistance and DC blocking diodes if it is a more then 1 receiver in/out type switch.

But I wont argue in this post about it, do what ever and try.

 

[Huevos]

2 motors would put the average FTA receiver over budget in the current draw on the power supply, unless the recivers you all use over there are different then here on this side of the pond.

They are not running at the same time. There is a switch before the motor and it will only send DiSEqC signals up to one motor or the other, not both.

And basic engineering 101, anything inserted into the system that is passive (not run by an external power supply independent from the supply from the receiver) will have both insertion loss in the over all RF signal and DC voltage loss due to it's internal DC resistance and DC blocking diodes if it is a more then 1 receiver in/out type switch.

Six of one, half a dozen of the other. Typical insertion loss of a switch is less than 3dB. At 2GHz (the high end of the IF) 3dB equates to 10 metres of cable, so if routing the cable through the motorised dish motor and switch at the back of the house and then on to the front of the house causes the cable to be more than 10m longer, the loss budget between the receiver and dish at the front of the house will be greater than the method suggested in post #2. BTW the motor itself is an unnecessary insertion loss to the dish at the front of the house if you wire it how you suggested.

Also the DC blocking diodes don't stop the current flow through the switch, they just stop it getting in the control circuits. As far as the DC going through the switch is concerned the switch is a dead short.

Edit: I've just done a quick test to see the exact figures we are talking here. Using a Spaun SUR 420 G, tested the resistance across the switch with a multimeter. Loss is 0.0 ohms. That's the DC loss that the motor sees. Testing at RF using Emitor Satlook Color HD at 12.607 GHz, (that's 2.007 GHz IF), testing with and without the switch inline the difference in signal is 1dB, which equates to about 10 foot of cable. And don't forget the switch is going to be inline for RF in both cases anyway which defeats the argument about RF losses through the switch.

 

[Terryl]

They are not running at the same time. There is a switch before the motor and it will only send DiSEqC signals up to one motor or the other, not both.

Six of one, half a dozen of the other. Typical insertion loss of a switch is less than 3dB. At 2GHz (the high end of the IF) 3dB equates to 10 metres of cable, so if routing the cable through the motorised dish motor and switch at the back of the house and then on to the front of the house causes the cable to be more than 10m longer, the loss budget between the receiver and dish at the front of the house will be greater than the method suggested in post #2. BTW the motor itself is an unnecessary insertion loss to the dish at the front of the house if you wire it how you suggested.

Also the DC blocking diodes don't stop the current flow through the switch, they just stop it getting in the control circuits. As far as the DC going through the switch is concerned the switch is a dead short.

Edit: I've just done a quick test to see the exact figures we are talking here. Using a Spaun SUR 420 G, tested the resistance across the switch with a multimeter. Loss is 0.0 ohms. That's the DC loss that the motor sees. Testing at RF using Emitor Satlook Color HD at 12.607 GHz, (that's 2.007 GHz IF), testing with and without the switch inline the difference in signal is 1dB, which equates to about 10 foot of cable. And don't forget the switch is going to be inline for RF in both cases anyway which defeats the argument about RF losses through the switch.

Sorry but a SUR 420 G is not the same thing as a standard Diseqc switch that is available over the counter at the local sat shop, that is a true RF relay, of course there wouldn't be a DC resistance through it, you have true mechanical contacts.

Compare apples to apples, try a standard Diseqc switch like his 1.0.

 

[Huevos]

try a standard Diseqc switch like his 1.0.

I've just checked a Spaun SAR 411 and that is a DiSEqC 1.0/2.0 switch. It too has 0.0 ohms resistance.

For me it goes without saying that if you use cheap and nasty Chinese switches that you are going to have problems with them sooner or later (normally sooner than later) whatever configuration you use them in.

 

[Terryl]

I've just checked a Spaun SAR 411 and that is a DiSEqC 1.0/2.0 switch. It too has 0.0 ohms resistance.

For me it goes without saying that if you use cheap and nasty Chinese switches that you are going to have problems with them sooner or later (normally sooner than later) whatever configuration you use them in.

I cant control what is available over here to the common consumer, the Spaun line of switches is only available through special order at most supply houses.

 

[Huevos]

I cant control what is available over here to the common consumer.

No one stocks them here either. I buy them direct from Germany. I think we have come to the tipping point (no pun intended) with people selling rubbish, where it seems there is now greater demand for cheap rubbish that isn't fit for the purpose than quality goods that will last the duration.

 

[Captain Jack]

Thanks Huevos! Just fitted my ancient DiSEqC 1.0 switch and followed your instructions above. It's working perfectly I like the instant switching between 28E and other sats. T90 anyone?

 

[Vipersan]

FWIW ...
My complex system uses the exact config as Huevos suggest ..
I drive 2 motorised dishes ...a TD110 ..and a TD88 ...through a diseqc 1.1 ....8 way switch .
In order than I can see the whole arc ..
The dishes are some 30 mtrs apart ..and I need this config as I have obstacles preventing each dish seeing the whole arc ..
Essentially the TD110 does the western half arc ...
The TD88 does the East..
All my receivers can use this config without issues ...as only 1 dish is ever in motion at any time..

Plus there are 6 other inputs for fixed dishes ..(not all in use _yet_ )

rgds

 

[Huevos]

I drive 2 motorised dishes ...a TD110 ..and a TD88 ...through a diseqc 1.1 ....8 way switch .

I just had a look at a cheapo, no name switch, and that is rated at 500mA power pass which is plenty to power an LNB and a DiSEqC motor.