Big dish v. Little Dish

[Gyn_Paul]

It sounds like a no-brainer, but I wonder.  I live in the centre of France, and have had decent reception with 80cm dishes when properly aligned, with the usual loss of signal during end-of-the-world storm systems when they progress our way from the south.

In an attempt to curtail this loss, I changed my main dish to 120cm, and frankly found little improvement. We still lose everything during storms (perhaps not for quite as long) but the trade-off seems to be that we seem more prone to losing channels which I judge to be on the 'edge' of the signal beam.

Is it my imagination, or is the 120's narrow beam acceptance less able to find all the transponders on all the satellites ?

I ask now because I'm about to replace an octo on the 120, and am considering changing it back to a good old trusty 80cm.  Am I being daft?

paul

[ericd]

Paul. It might be the right time to carry out a little census on a) Name of nearest town b) Dish dimension c) reception quality.

I will add my bit when I go to our house in next 10 days.

[andyh4]

Paul

contrary to what seems like logic, the bigger the dish, the more important it is that it is accurately aligned.

It could well be that you are just a smidgen off the optimal and that by increasing the size of the dish you have effectively magnified the error from the optimum.

[Gyn_Paul]

[quote user="ericd"]Paul. It might be the right time to carry out a little census on a) Name of nearest town b) Dish dimension c) reception quality.

I will add my bit when I go to our house in next 10 days.[/quote]

23160 Bazelat (nearest town would be La Souterraine) 120 cm reception: uneven !

I've spent hours micro tweaking the dish to get - what seems to be - the best compromise, which is why I wondered if a narrow beam attenuates the weakest transponders (those on the tightest footprints) on the satellites on either 'end' of the 28.2E cube ?

[Gardian]

NE Gard (so pretty far south), 1.15m & professionally installed & aligned.

Never had a problem, with excellent reception except during the most violent of thunderstorms (when its wise to shut everything down anyway!)

[woolybanana]

Pas de Calais, deep in a valley, UK dish is 80 cms, Fr dish is a bit smaller, perfect reception, except when the storms are really violent.

(The dishes were already here when I bought though one was not in use.)

[Jonzjob]

Just NE of Carcassonne. 120 dish, I think, pro installation and no problems, with the exception of the heavy storms everyone gets.

The bigger the dish, the more accurate it has to be aligned and with a 120 it's best done by a pro. It won't take long and an enquiry would tell you if ti's worth while?

[Martin963]

This is a subject I've been "studying" this year Gyn_P,  but not on Astra 2.

I acquired in February a sat receiver capable of picking up the 5 deg W multistream feeds,   the two transponders that carry all the TNT transmissions to feed the UHF network on the ground.   They aren't scrambled,   but they use a technology that grew out of the original Newtech "concentration" system,   where effectively three normal MUXs are combined and put on one transponder.   The six terrestrial MUXs therefore need two transponders.   Only a handful of receivers can "undo" the multistreaming.

I say all that because back in England they seemed to come in fine on a 60 cm dish,  although it was a dry spring with few heavy downpours.

Arrive in France and they're constantly falling over,   particularly in the heavy cloud before a downpour.  

So I move from 60 cms to 80 cms,  the signal quality improves a bit,   but they still fall over pretty easily.    So I move to a 1 m dish,   by this time the Fransat receiver on another of the LNB's outlets is practically glowing in the dark,   but even on a 1 m dish the multistreams will fall over if the rain is really diluvian.

The reason:   the error correction and other parameters on these feeds are pretty flakey,  so the margin for problems is very small.    Fransat on the same satellite busts through on the 60 cm dish because it's got more robust parameters....

I suspect the same thing is happening for you.   Using the same receiver on an 80 cm dish on Astra 2,  the BBC and ITV HDs carry on as the quality drops in rain,  (whereas on multistream nothing works if the quality drops below 68% (it simply collapses then to zero)),   the Astra 2 HDs will run even at 50%.    Below that they go,   but the SDs carry on and will run at 35% without problem.    When they go,   I'm left with the stuff like Sky News on the pan-European beam.

So my experience suggests that you're going to have to go VERY big to have completely uninterrupted reception on transponders (like the HD ones for Freesat) which are set up to run at the limit of what's possible on the spec for DVB-S2 error correction.    In the case of the French TV multistreams the TDF UHF sites have 1.8 m reception dishes,   and the relays where they use the feed have at least 1.5 m.    Presumably that's considered enough,  as TDF can't afford (literally) to lose the UHF network every time there's a bit of rain....   

[ericd]

In Laguepie 82250. Sky region 2 dish (Elliptical mesh 73cm x 58cm). Excellent reception in clear weather (World Championship last night). None to very bad in bad weather. French tv is on a separate same dish and no issues.

[ericd]

In Laguepie 82250. Sky region 2 dish (Elliptical mesh 73cm x 58cm). Excellent reception in clear weather (World Championship last night). None to very bad in bad weather. French tv is on a separate same dish and no issues.

[Jako]

In 23160 Bazelat a good 60 cm dish will be fine. You are still inside Sky zone 2 .

An 120 cm dish is too big, the signal strength too strong and probably overloading your receiver resulting in a bad signal...

[Chancer]

[quote user="Jako"] An 120 cm dish is too big, the signal strength too strong and probably overloading your receiver resulting in a bad signal...[/quote]

 

Interesting logic [blink]

[AnOther]

Might not be the cheapest option but using top quality coax will potentially out perform an increase in dish size whilst avoiding the pitfalls mentioned.

Reducing cable loss by 3dB is roughly equivalent to going from an 80 cm dish to 120cm !

[Lehaut]

We are moving into a residence where dishes are not allowed. Out of interest, are these any good (would be in Nantes) for UK TV?

https://www.reichelt.com/fr/fr/?ARTICLE=99942&PROVID=2788&gclid=CjwKCAjwuvjNBRBPEiwApYq0zpMlfibRC-iTnu5JXRGQ_OFub983T0m-7OfGv11LrOoyv1LWR5rPsBoCPzcQAvD_BwE

[Chancer]

Are these any good?

 

Do you mean at being invisible (only to the blind) or at convincing sighted people that they are not a dish?

 

I would say no good at either!

[suein56]

My friend lives in apartment where dishes are not allowed so she bought a low wooden planter with a sturdy back trellis and my OH fixed her circular dish to that.

We have pale cream crepi so have a pale cream, oval, 45cm mesh dish which is the most 'disappearing' we could find.

Looking at the flat dish you have mentioned it does seem likely that it might appear less noticeable

Will you have a balcony, would a trellis fitting be possible ?

Sue

[Chancer]

In the UK I would have had to have the dish on the front of the house which was completely unacceptable to me back in 1992, I fitted it just above the rear of the side carport that I had built, because the house is at the top of the hill the dish is completely invisible from the road and footpath.

 

Since then most people have lowered the tone of the place with dishes mounted on the front of their dwellings in the most inappropriate places by the lazy installers, cables draped across the frontages etc.

 

Blocks of flats with paraboles everywhere look awfull but the building owners should provide a rooftop distribution system before prohibiting paraboles.

[Gyn_Paul]

You wouldn't say that, Jako, if you could see the gradual pixilation and eventual freezing every time a storm cloud forms over North Africa !

After close inspection, I have a feeling that one of the huge oaks on the edge of our drive has lurched to the east during the storm when I was in hospital for a month, that plus 12 year's growth has possibly pushed a branch or two to the beam path (I wish it was as easy to eyeball the beam angle with an offset dish as it is with a prime focus one!).

The solution would be to move the dish mounting further (eastwards) along the barn wall, but - naturally - the 8 cables run the other way so would all need replacing. Even thinking about that makes my head hurt!

paul

[Lehaut]

To answer chancer, I asked if they would be any good for UK TV (reception). Visibility to sighted or unsighted persons was not part of the question. The balcony in question is not over looked but is too small for a normal dish. (thank you for the suggestion Sue). I had hoped for a more enlightened comment from a genuine question. There appeared to be contributors in the thread with more techinal knowledge in this area than l have, or perhaps I am missing the aim of this forum?

[Danny]

Lehaut,

There is no simple answer for you. It will not be as effective as a larger dish for good reception in your area but it may just bring in enough signal for the various UK channels if well set up.

Reception gets more difficult for smaller dishes as you get further south from the UK.

It does have a single LNB integrated. If you need more than one cable output you will have to go for another model - double or quad - available on the same site but more expensive.

It seems to me to be a case of suck it and see!

Danny

[Lehaut]

Thanks Danny, thought it looked too simple and the wrong shape for an easy answer. Have never seen one on a house/flat/camper.

Only need a single LNB.

[Martin963]

@ Lehaut

Actually I don't see why it shouldn't work....  It says it has a gain of 32 dB which I think is comparable to a 45 cm "Sky" dish.   You're installing it in Nantes which is well north of the line where reception starts to fall off a cliff (roughly Bordeaux - Lyon - Geneva),  and although I suspect reception might collapse in a heavy rain storm I'd say it would work the rest of the time. 

Laters:   It's probably stating the bleedin' obvious but your balcony should have an unobstructed view in a SSE direction,  and be able to see the sun mid morning in late October or mid Feb (ie no buildings or trees in the way).

[ericd]

My 45cm Sky "Region 2" dish works well (see somewhere above) in Laguepie 82250.

We have 2 x such dishes one for FrenchSat which works wells all the time and one for UK television which works well, except in very bad weather.

[Lehaut]

@Martin963

Thanks, will stand on the balcony and look for the sun!

145° in old money?

[Jako]

[quote user="AnOther"]Might not be the cheapest option but using top quality coax will potentially out perform an increase in dish size whilst avoiding the pitfalls mentioned.

Reducing cable loss by 3dB is roughly equivalent to going from an 80 cm dish to 120cm ![/quote]

No, it does not. Cable loss is quite irrelevant as both the signal and the noise are dampened by the length of the cable. Unless the cable length is very long and the signal strength gets below a threshold level where the tuners amp can no longer compensate. The only thing relevant is the signal to noise ratio.

A bigger dish makes the signal stronger without adding more noise. And that is what you need if the signal is too weak.