where to put the diseqc switch

closetosoton

closetosoton

More dishes than Sense.
Messages
502
Likes
0
My Satellite Setup
Wavefield T55, 20 LNB's and a whole load of analogue boxes!
My Location
Close to Southampton
#1
I must say this is one of my favourite forums at the moment....

Anyways - techinical one for you - the switch quotes insertion loss of 3db, does it matter whether its closer to the receiver or the dishes/lnbs?

Obviously being closer to the receiver means running twin cables virtually all the distance... but I've read somewhere its better to put it closer to the dish/lnb end - why?

CtS
 
A

AdinHH

Regular Member
Messages
14
Likes
0
#2
I'd say because it makes everything tidier and easier to manage when it comes to cabling. You only have relatively short lengths from each LNB to the switch and then you only need to worry about 1 cable running from the switch into the house. Where else could you put the switch? It just makes it easier to manage when you fix it somehow to the dish mast or a location close by.
 
closetosoton

closetosoton

More dishes than Sense.
Messages
502
Likes
0
My Satellite Setup
Wavefield T55, 20 LNB's and a whole load of analogue boxes!
My Location
Close to Southampton
#3
AdinHH said:
Where else could you put the switch? It just makes it easier to manage when you fix it somehow to the dish mast or a location close by.
I could put the switch at the back of the receiver - since not all my dishes are co-located the switch can't really be next to all lnb's. I just wanted to know if there was a technical reason as to which was the better solution.

-cts
 
Analoguesat

Analoguesat

Administrator
Staff member
Messages
45,902
Likes
8,489
Location
Scottish Borders
My Satellite Setup
TM 5402HD
Skybox F3
Sky+ UK.
My Location
Scottish Borders
#4
Mines about half way along my cable runs - mainly for protection from Scottish monsoons (there was a handy place to put it).

3db loss is half the signal theoretically isnt it (I havent seen any problems with my signal levels, just channel hopping takes a little longer sometimes when the channel changes polarity)
 
rolfw

rolfw

Believe it when I see it Admin.
Staff member
Messages
37,723
Likes
1,291
My Satellite Setup
Technomate 5402 HD M2 Ci, DM7000s, Transparent 80cm Dish, Moteck SG2100 DiseqC motor, lots of legacy gear. Meters: Satlook Digital NIT, Promax HD Ranger+ spectrum analyser.
My Location
Berkshire
#5
Most of them recommend being a metre from the dish, but you can get away with what you have to. :)
 
PaulR

PaulR

Dazed and Confused Admin
Staff member
Messages
15,868
Likes
3,150
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
#6
Have to gree with AdinHH, the switch is normally near the dishes to make a tidy installation - and also to save on the cost of all the extra cable if it were any nearer!

PaulR
 
closetosoton

closetosoton

More dishes than Sense.
Messages
502
Likes
0
My Satellite Setup
Wavefield T55, 20 LNB's and a whole load of analogue boxes!
My Location
Close to Southampton
#7
rolfw said:
Most of them recommend being a metre from the dish.
but why....?
 
closetosoton

closetosoton

More dishes than Sense.
Messages
502
Likes
0
My Satellite Setup
Wavefield T55, 20 LNB's and a whole load of analogue boxes!
My Location
Close to Southampton
#8
In seeking the RF answer I asked an RF engineer: he said:

"The loss is due to the selected cable path, so will be the same for both cases, as the total length LNB to RX is the same. Running 4 cables parallel to each other for a long run may degrade isolation, but this may not matter. The main point is you will need less cable with the switch near the LNBs, so so preferably do it that way."
 
rolfw

rolfw

Believe it when I see it Admin.
Staff member
Messages
37,723
Likes
1,291
My Satellite Setup
Technomate 5402 HD M2 Ci, DM7000s, Transparent 80cm Dish, Moteck SG2100 DiseqC motor, lots of legacy gear. Meters: Satlook Digital NIT, Promax HD Ranger+ spectrum analyser.
My Location
Berkshire
#9
closetosoton said:
but why....?
Don't know, but I guess that anything with an insertion loss, is better being close to the signal source, but it doesn't appear to be a problem if the switch is further away.
 
closetosoton

closetosoton

More dishes than Sense.
Messages
502
Likes
0
My Satellite Setup
Wavefield T55, 20 LNB's and a whole load of analogue boxes!
My Location
Close to Southampton
#10
rolfw said:
Don't know, but I guess that anything with an insertion loss, is better being close to the signal source, but it doesn't appear to be a problem if the switch is further away.
I have had another response for an RF type person:

"Should not matter one way or another: since the switch is basically a
passive device its contribution to noise figure will be the same
wherever it is placed. There might be some slight subtleties depending
on the Return Loss presented to the cable by the different switch ports,
but really not worth worrying about.....

Incidentally, unless your cable is phenomenally long or your receiver
even deafer than it should be, an increase in LNB to receiver loss of
3dB or even 6dB should not make a blind bit of difference to received
error rate/picture quality, as LNBs are normally designed to provide
enough excess gain to overcome the loss of said phenomenally long
feeder."
 
Top