2D reception in France

[Francophile]

Hi Guys
I'm new to the forum and hoping for some advice from experienced users. I have a mobile home in Frejus, southern France. In February I set up a Triax TD88 dish, with universal lnb and Amstrad Sky box. After careful set up of dish & lnb skew I managed 55/60 % signal strength & 30/35% signal quality. This provided good reception on BBC London,BBC2,ITV,CH4, CH5 with FTV Sky channels from Astra 2D. The extra ITV channels were there but pixilating badly. The setup worked the same at Easter. When we arrived for our main holiday two weeks ago only CH5 and FTV Sky channels available . The signal strength and quality bars appeared to be registering as before, as we were on our main holiday the family were non too keen on me "wasting time" tweaking the dish so it was left alone, least I got to see the highlights of the thrashing of the Aussies.
Now I know the reception where I am is marginal and the dish may have moved slightly so if I fit a larger dish will i have more margin for error re slight dish/satellite movement? If i increase dish size is improvement in signal quality proportional to gain, how much extra gain would i need to improve signal quality by 15/20%? My current dish quotes gain at 38.8db. If I go to a 1.2m dish (this is the max I can go to) I will get gain figures of 41.3db (Gibertini 1.2) Ideally I would like a lightweight aluminum dish around 1m in size, any larger and I will have to ground mount. Any suggestions re dish size & lnb combinations please

[Analoguesat]

A bigger dish will give you LESS tolerance of dish movement! This is because bigger dishes have narrower incoming beamwidth tolerance

[Francophile]

Ahh!! So basically the larger the dish the more critical alignment is ?
Is that because the signal i want is weak or that the bigger dish picks up more "unwanted noise"

[Analoguesat]

Correct - bigger dish - more critical alignment

Neither - the bigger dish has a smaller "acceptance angle" for incoming signals. (And remember the incoming signals are phenominally weak - tthe transmitters on the satellites have about the same power output as a 100W lightbulb!)

[Francophile]

Wow it's amazing we pick up anything. I understand now the larger dishes will not give reception if moving slightly out of alignment and need to be spot on and securely mounted. A larger dish will give me extra gain and hopefully improved signal quality. I do not understand how much improvement I will get, ie how significant an extra 1.5dbi will be. It does not sound much?

[Analoguesat]

A 3dB increase is equivalent to doubling the incoming signal strength.

[Francophile]

That's a significant improvement, which should give me what I want to acheive. Thanks for your advice much appreciated.

[Robbo]

Yep, 1.5dB doesn't seem much, but t could be the difference between pixelation and not. There is certainly a notable difffence between a 1m dish and an 80cm, the 1m dish is actually one and a half times the area of an 80cm.

The acceptance angle or 3dB beamwidth difference between the two is about 0.5 degrees, so alignment won't be very dissimilar in difficulty.

[Low Profile]

A TD88 should be fine for 2D reception in Frejus (so long as it's not raining), but you might find that if you peak up on 2D then signals from Eurobird will drop out. Sometimes it's worth aligning your dish between the two satellites or peaking on your weakest transponder, the problem with this is that you will then become more susceptible to rain drop out. Good luck whatever you decide to do.

[PaulR]

Just a thought.

Is the receiver you're using a $ly Digibox? And does that Digibox lie switched off between holidays?

If yes then the Digibox has probably missed a few over-the-air software upgrades and this could be causing the missing channels problem.

[BombedOne]

It's very hard to say, how many % gain is per DB for different receivers. According to my observations, 1DB roughly gives 10-15% signal Q increase. Depending on receiver.

[Francophile]

Thanks for the info, I suspect the dish may have gone slightly out of alignment, but I feel moving to a 1m quality dish with low noise LNB is the way to go. The box I have is an Amstrad Sky box and it is left powered down between visits. Not sure how I can get round this, is there a method of rebooting, or forcing updates that I can follow?

[Robbo]

Could also be that the box has gone faulty. Are you using it to watch Sky, or just the Free channnels? As you could just get a digital FTA sat box instead.

[Francophile]

Using the box for the free channels only. Able to watch CH5 & the Free to view Sky channels, but seem to have lost BBC & ITV. I have an older Panasonic Sky box there, which gave me the same results leading me to suspect the dish has moved slightly rather than a box fault!