BBC 2D or not 2D??

sayireland

Funny situation here I hope someone can throw some light on.

As of now it seems that the BBC are double lighting on both Astra 2A and 2D.

10.773H is a mirror of 11.720H
10.803H is a mirror of 11.798H

All fine except that the horizontal frequencies, including RTE, on 2D disappear for me here in Madrid in the evening time

(BTW if anyone can help with any idea about why I have the vertical frequencies 24/7 and the Horizontal no and how to fix it, I would be very grateful and it would certainly save me a hell of a lot of money to get a 1.8 dish which I don't have a 100% guarantee will work)

However having got for example BBC Radio Cymru added in the add channels from the 2D frequency when reception was good in the morning I proceed tonight to check, obviously expecting it not to be there but it is no problem.

This has also been reported on the www.satellites.co.uk forum as well by some people fro Scandanavia (where surprisingly enough they ave the opposite scenario to me where they have the Horizontal frequencies 24/7 but not the vertical ones).

sayireland

Another point about what I mentioned above is that when I access BBC Cymru through the add channels I get a message saying 'Further schedule information is not available' (the same message I get from 2FM) but I get the sound whereas when I go to channel 904 I get the programme info no problem and of course the sound as well.

seano

Question and answer

DROP OUT WITH ASTRA 2

I have a reception system consisting of a 1.4m offset antenna (SMW), an SMW-LNBXL-800C with 0,65-0,80 dB and an Echostar AD-3000 IP. According to the footprints published in TELE-satellite the signals of ASTRA 2A (28.2° East) should come in clearly even in southwest Germany. Actually, however, I can only occasionally receive TCM and Boomerang on 12.051 V, for example. The signal level meter varies between 32 and 43%, the signal quality between 24 and 30%. Most of the time, however, the values are even below that and all I can see is static blocks on my screen.

What could be the reason for this? The dish is perfectly aligned, and I cannot find an explanation for the varying signal meter values on my Echostar (not only for the frequency mentioned above). Unfortunately Echostar does not answer any of my questions and here where I live there is no specialized dealer who I could ask for assistance. Maybe a better LNB could help? I‘ve read about LNBs with 0,3 dB in TELE-satellite. Is such a thing really available and what good does it do?

ANSWER

No, simply changing the LNB would hardly solve your problem. It seems as if a so-called „sat slope“ could do the trick. It works like an equalizer and balances certain peaks and dents in specific ranges of the IF. Johansson and Global are two of the manufacturers of such small, inexpensive but all the more useful tools. The „sat slope“ is simply connected between the IF input and the coax cable

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No gaurentee that it works but it only costs 21euro

Capt'n Midnight

I saw somewhere - can't remember where that the solar panels on the satellite are re-orientated towards the sun so during the day the satellite rocks back and forth - which affects the beam in the evenings - probably hogwash but it is slightly plausable.

watty

All satellites are also on a slightly inclined orbit. To normal reception it is no bother. On a very big dish you might even need a tracking motor that slightly bobs the dish up and down over the 24 hrs.

The more inclined the orbit, the larger the apparent up/down "bob"

The larger the dish, the more sensitive it is to "bob".

If you ever tried to align a very big dish you know what I mean. Even here in Ireland the 60cm minidish is MUCH easier to align than my 1m dish.

If the 1m wobble slightly in gale, no picture. If the minidish wobble a lot in gale (unlikely as it small) then it don't matter!

It is true that some Satellites have to reorientate their sails also for part of night are 100% in shadow running on batteries only. I can't imagine that this affects the signal. The combination of inclined orbit and large dish is likely.

An inclined orbit (I don't know why) saves some station keeping fuel. Very old satellites (Gorizont?) only work for an hour on a modest dish without the up/down tracking as the orbit is so much inclined.

Capt'n Midnight

fuel saving - older sats are allowed to drift further (up to a degree ?) to extend their life and if I remember it is a figure of eight pattern - but this usually applies to link feeds 'cos it is easy to have a ground tracking station track it's predictable path - but a tad complex for your average punter..

Station keeping - don't forget the moons gravity as well as the sun's acts on the satellite so it can't have a purely circular orbit - also from time to time the sat's panels can be eclipsed - predicatable and coverage depends on the battery size (it costs money to put things that only get fully used twice a year 36,000 miles up ) - so sats can use rocket fuel (or ion drive in the newer ones) to minimise the drifting.

Non-Technical Answer - "atmospherics"

sayireland

Thanks for the comments.
Will try a 'sat slope', could well be the solution as I heard of a guy in Italy who started getting a better picture with over 200ft of cable.

As regards the BBC I still don't get why I'm getting the reception. It would seem as if even though there is double lighting the 2A frequencies for the moment are working as default i.e even though I'm tuning in the 2D signals the reception is really coming from 2A.

watty

Longer cable attenuates the higher frequencies more (but 11.720 is a low frequency and 11.600 is a high frequency as the Sat box swaps band at 11.700).

The frequencies on the cable are:
Below 11.700 GHz subtract 9.750
Above 11.700 GHz subtract 10.600
For MHz leave out the decimal point.

The digibox hasn't changed to 2D (yet) it is still using 2A. But could change any time, I suppose.

[Pedant mode]
22,500 MILEs away above equator. multiply by 8/5 for km.

Simple inclined orbit on big dish: A motor bobs the tilt of dish up/down once in 24 hrs.

Figure 8 Inclined orbit: A motor bobs the tilt of the dish up/down twice a day.

A geared syncronous motor (like mains record player motor) will "keep time" well enough for quite long periods. Though the mains frequency "drifts" a percent maybe during the day the Electricity suppliers do keep the total number of cycles over 24hrs correct (for mains driven clocks), so once alinged a simple Up/Down gear will track. A cam would be needed to adjust the amount of Up/Down according to how inclined the orbit is.

I'm surprised if you can't buy such a thing for 2.5 or 3m dish as these will be VERY sensitive to the satellite orbit inclination, typically losing or weak signal once or twice a day.