Gang Up Two Ubc Satellite Dishes For More Signal?

[autonomous_unit]

Long story short, our house has two UBC satellite dishes with wiring off to two different rooms. The dishes are actually very close to each other, since that patch of roof has the best sight-lines to the sky.

Would it be viable and inexpensive to wire the two dishes onto one cable (with some sort of passive junction up at the roof location) so that a stronger signal could be sent down to one room (on a single cable) to reduce the effects of rain fade etc.? Or is the DSTV signal sensitive enough to signal path that this would not increase signal quality but rather cause distortion or cancellation?

[paulfr]

Long story short, our house has two UBC satellite dishes with wiring off to two different rooms. The dishes are actually very close to each other, since that patch of roof has the best sight-lines to the sky.

Would it be viable and inexpensive to wire the two dishes onto one cable (with some sort of passive junction up at the roof location) so that a stronger signal could be sent down to one room (on a single cable) to reduce the effects of rain fade etc.? Or is the DSTV signal sensitive enough to signal path that this would not increase signal quality but rather cause distortion or cancellation?

I am an EE but do not specialize in RF. So with that said;

I do not think so.

First the best you could obtain is a doubling of signal to noise ratio.

But this is usually set in stone at the detector/preamp at the focus of the dish.

So you really would not see any benefit IMO.

Each dish/preamp combo may have different performance, so just choosing

the one with better signal quality is probably your best bet.

Edited February 12, 2008 by paulfr

[monty]

I think that all the normal channels are on the same polarization (with exception of the DLTV channels), so there actually is no need for two dishes.

Just use a splitter, and make sure that the receiver connected to the power pass output of the splitter is always plugged into the mains (can be in standby).

I have 3 receivers connected onto 1 dish without problems!

In general there are only two ways to reduce the effects of rain fade, a bigger dish and/or a better LNB. In my experience, a high quality sensitive LNB, with a very good signal to noise ratio can do wonders for the reception!

The ones UBC installs are the cheapest mass produced LNB's they can find!

[Khutan]

What you are talking about is called co-phase. It is a technique commonly used for Radio Telescopes and deep space stuff. It is not easy to set up as you need the cables running from the LNB's to be exactly the same length. Or you need to use a Co-Phase tuner to make the cables the exact "Electrical Length" Doing this can be a difficult and frustrating exercise, and there are many variables to take into account such as the LNB angle and offset etc.

If you have dishes of varied signal strength, then you will have a problem of elevating the noise level.

I would check your signal strength on the box first from the good dish. If you are near maximum signal strength then you may be better putting a splitter on the cable and running the two boxes from the one dish - like I have in my house.

[Crossy]

Yep^^^ I reckon the hassle of attempting to use two dishes will FAR outweigh the gains, if any.

We're running two receivers off one dish with a simple splitter (both rx terminals pass power so we only need one box on).

[Phil Conners]

I have an 180cm solid offset dish for sale if you need a better signal Best offer gets it

[monty]

I have an 180cm solid offset dish for sale if you need a better signal Best offer gets it

Ex iPSTAR?

[LivinLOS]

Bigger dish is easiest way to better signal.. And yes large dish one cable and a splitter should be OK..

[autonomous_unit]

OK, thanks. Particularly to the couple who decoded my question best! :-)

I already have two dishes and they work fine with separate receivers, except dropping out intermittently during the rainy season. Each receiver showed full "255" signal strength last time I checked them. I have been considering dumping one of the receivers (one gets just the local Thai channels for extended family and hardly sees any use) and was wondering if it was worth trying to keep two dishes active to double the surface area for those rainy days.

The idea would have been to put an electrical junction on the roof equidistant between the two dishes and run the output of that down the single cable to the room with the remaining receiver... I was afraid there would be subtle phase issues, as Khutan pointed out. Not being an RF engineer, I don't have intuition for what the error margins are and whether they are significant for two ostensibly identical dishes and a basic bit of cable cutting and terminating by me...

The responses do raise another idea though... would a signal splitter on a regular UBC dish allow two receivers to work most of the time? The biggest reason our second receiver gets little use is that it turns out nobody likes to sit in that second room for very long to watch the smaller TV. Maybe I should move both receivers to the same room, so one is always available for local channels while the other becomes dedicated to my MythTV installation I mentioned in another thread this week (for recording/time-shifting the western programs)... but I don't want to tear the place up to route another cable down to the same room again...

[Crossy]

The responses do raise another idea though... would a signal splitter on a regular UBC dish allow two receivers to work most of the time?

We have just that setup, it doesn't seem to go off any earlier when the rain starts so the 'halved' signal has no visible effect. I also decided not to take UBC True up on their 'offer' of something like 4k for a second card and got a card splitter (shhh! don't tell anyone) works very well, all channels either box although the bedroom box seems to spend all its time on the 'free' channels

[Phil Conners]

I have an 180cm solid offset dish for sale if you need a better signal Best offer gets it

Ex iPSTAR?

No, actually ex. Agila2 (Dream). It worked fine at my old house but when I moved house the installer insisted I needed a 220cm center mesh dish and I was dumb enough to buy it.

I think the Ipstar dishes are usually 100 cm center dishes, no?

[astral]

A bigger dish is the answer.

180cm is overkill. 100cm should do the job.

3x the area of the ordinary 60cm dish that UBC supplies.

Make sure the new dish is solid, not mesh.

Mesh is fine for the lower frequencies of C band, but not for Ku band which is used by UBC.

[Phil Conners]

Actually mesh is fine for both Ku and C band. Surely 180cm may be an overkill, I just wanted to plug my old (solid) (offset) dish in case someone was interested ... bigger is always better

[Crossy]

Actually mesh is fine for both Ku and C band. Surely 180cm may be an overkill, I just wanted to plug my old (solid) (offset) dish in case someone was interested ... bigger is always better

Only if it's a fine mesh dish designed for Ku. With a C band dish the holes are too big (greater than 1/4 wavelength) and Ku just drops through

[zzSleepyJohn]

Only if it's a fine mesh dish designed for Ku. With a C band dish the holes are too big (greater than 1/4 wavelength) and Ku just drops through

My old C-band mesh dishes seem to work OK when I put a KU LNB in them, even on non-Thaicom birds. The only problem I found was slight irregularities in the surface that have developed over the years cause some sidelobes, so one bird exhibited several maxima as I moved the dish across the sky. Worst case scenario would be interference from an unwanted sidelobe, but there aren't that many KU birds covering this region.

+ SJ

[Khun Jack]

I have an 180cm solid offset dish for sale if you need a better signal Best offer gets it

Have seen some 180 cm dishes (not offset) in the Amorn shops for 3400 baht.

For a 180 cm offset solid Ku band dish without damages my offer is 2000 baht.

Edited February 16, 2008 by Khun Jack