Astra 2E: Iberia & Balearics Reports

Status
Not open for further replies.
Re the Invacom adjustable feedhorn - would extending the threaded area more along the collar and winding the disk further down change the f/d ratio to any advantage for a larger dish
 
Like I keep saying the problem is with the bore, not how it is adjusted.
 
joddle said:
Re the Invacom adjustable feedhorn - would extending the threaded area more along the collar and winding the disk further down change the f/d ratio to any advantage for a larger dish
Click to expand...


Shirely the real problem is how to hold the signal meter while you are making the very fine adjustments.



Not so many meters with neck straps these days. :)
 
hexah: with PF, you adjust a bit, get out of the way then measure ;) but yes its a pain, lost count of how many times the SH200 fell because of that.

I've been studying feedhorn theory, and have to agree with Huevos, considering the same frequency band, bore is what changes the beamwidth (F/D)
the position of the choke rings offer just marginal adjustment.

if anybody can answer:
what is the Famaval entry bore, does it go to 17,5mm on the flange side?
total length, total diameter, and how much does the center feed projects over the choke rings
 
Last edited:
Feedhorns and LNBs are always a compromise over any frequency range.

The basic principle is being lost here.

The feedhorn and LNB are minor parts of the system, the gain provided by the dish is the most important part. Fiddling around with the minor parts of the system is fiddling while Rome burns.
 
hexah said:
Feedhorns and LNBs are always a compromise over any frequency range.

The basic principle is being lost here.

The feedhorn and LNB are minor parts of the system, the gain provided by the dish is the most important part. Fiddling around with the minor parts of the system is fiddling while Rome burns.
Click to expand...

Very true. But sometimes it does pay to fiddle - and the fire is extinguished ;). I can testify to that from my own personal 'fringe' experience where a bigger dish was an unwanted option.
 
The usual nightmare of sitting down to watch something when its been fine for a week then suddenly the little squares start appearing and loud farts on the sound. :(

Yes that's the annoying thing, not having a bigger dish.

I can assure you it is worse to have it and to risk death to even mention putting it back up. :-Axechase
 
For some reason I seem to have lost rcception of all channels except Channel 5. Heavy cloud but no rain. I've seen similar reports of a weakened signal from others in France, Spain and Germany :(.
 
C5 is on 2F, the others are (mostly if not probably) on 2E. One of the slight differences between 2E and 2F no doubt.
 
It's not a slight difference. I can't get a lock on any transponder right now - neither 2E nor 2F.
 
Nagusia said:
For some reason I seem to have lost rcception of all channels except Channel 5. Heavy cloud but no rain. I've seen similar reports of a weakened signal from others in France, Spain and Germany :(.
Click to expand...

My signals were down too, although i'm still receiving them, but its very near the threshold of no picture, noticed it over the weekend and just been out to have a twiddle but made no difference
 
It would appear to be a common occurance across the region. I have contacted Huevos who has noted approx 0.5dB loss on average, in my area it would appear to be 1.5 dB loss, "summer effect"? Do not know yet, but will continue to test my own dish and others I have fitted locally. Seems to be affecting offset and pf with equall effect.
 
Some cheap Chinese LNBs had orange caps. They would blend in very well.

Televes used to sell orangey coloured dishes that could match the orange clouds nicely.
 
Brian Philpotts said:
It would appear to be a common occurrence across the region. I have contacted Huevos who has noted approx 0.5dB loss on average, in my area it would appear to be 1.5 dB loss, "summer effect"? Do not know yet, but will continue to test my own dish and others I have fitted locally.
Click to expand...

That is why (yet again) there is a sudden surge in interest in feed horns, plus LNB sensitivity and receiver sensitivity.

Feed horns are the classic sign of distress. They gather the signal and reject some noise. They are basic and proven technology. You use the one the dish manufacturer made unless you have excellent reasons not to do so (i.e. not some vague hope). Fiddling with it to try and drag in +0.01 dB is usually a sign of utter desperation and possibly the spark that causes extreme domestic violence when retarded drivel like Coronation Street and Eastenders is not being received.

People may get lucky fiddling but the signal is still likely to be marginal and it means what it usually means and that is to increase the gain of the signal.

Which means more signal coming in, which means a larger dish.

Still, given the expense and upheaval of installing a larger dish (if its even possible) then I suppose people must clutch at straws try to optimize as much as they can.


Brian Philpotts said:
Seems to be affecting offset and pf with equal effect.
Click to expand...

The worries about offset vs prime focus go back to last century and the early days of satellite. There are still various issues with offset antenna around wind loading, mechanical strength, noise factors, size and installed footprint, overall mass, use with polar mounts and more that are significant for professional users. Most don't affect the hobbyist.

The important bit is that offset dishes lie flatter to the wall which looks less obtrusive and also helps to shed snow in affected areas.

For dishes bigger than about 1.5m to 1.8m then prime focus is preferred and for professional use pf is generally preferred.

Basically here it doesn't matter regarding the signal strength received, though it is somewhat easier to twist an offset and have it slightly off axis which may affect weak signals. If it has been installed properly with proper attention to plumb-ness and stringing, and as it is not at the ends of the arc where care installing it becomes more critical, then it should be o.k.
 
I have been at this satellite lark for coming up to three decades now, more if you include the anticipation of reading the reports in Television magazine, etc.

I am still amused that many people in Spain particularly are failing to understand some of the basics of big dish use. I am not criticizing you here, I mean the kind of installer who turns up on a horse wearing a large stetson (I suppose it keeps the sun off!).


Read my reply on another astra thread, on receiving Astra 2E on a 2.4m dish post #209

http://www.satellites.co.uk/forums/threads/astra-2e-western-europe-reports.159945/page-11

If they are going to space out the satellites a bit more it will create problems with big dishes because of the narrow beamwidth.

If they are more than 0.2 degrees apart it may be necessary to have two large dishes to receive them consistently with enough gain to ensure reception at all times.

Remember that the satellites wander around in their 'box' in the sky and you have to take that into account.

Atmospheric electrical thermal noise and man made background electrical noise and aliens trying to contact us from outer space on a bad choice of frequencies :rolleyes: is something we can't do much about except try to drown it out with a big dish and to ensure proper shielding in the cables (removal of the foil and making sure the braid wire is evenly distributed around the cable before putting the F connector on, if its not a crimped f connector a decent amount of self amalgamating tape and a drip loop will stop it sliding out under its own pressure).


The principle of beamwidth selectivity is fundamental to using a big dish. And so is the satellites annoying tendency to wander. Thats why a big dish (from 3m to 6m) in a professional dish farm can remotely adjust for inclination.

What I am saying is that what few people seem to realize, despite installing these dishes for years, is that if you want to get weak signals from co-sited satellites with big dishes there is a point where you have to use two or more big dishes due to the narrow beamwidth and the need to provide enough gain to ensure constant reception (and so avoid domestic violence).

In my view this effect means that once you go over about 1.5m then you are better off assuming a 0.1 degree granularity in KU band no matter what the published specification says because there are so many factors that plague weak signals.

Recall that the mid band circa 11.5GHz specification for 3dB beamwidth at 1.5m is around 1.2, at 1.8m its 1.0, at 2.7m its down to a narrow 0.65 degrees. With my ancient 2m dish the polar mount has a massive threaded bar easily four times as thick as the ones they use today. But even with that room to manoeuvre on weak signals selectivity is surprisingly sharp.

So the unfortunate truth is that once you need to use dishes in the 1.8m to 2.7m bracket and above then if you really want reliable 24/7 reception which I assume is the aim then you have to do what the professionals do and that is to use two big dishes.

If you want 24/7 reception there is no way around that as you cannot ensure enough gain and good CNR and MER any other way. (MER measures how much the weak signal has been mangled on its way to the receiver).

Also bear in mind the advice I keep giving and that is to find out what dish size people use and try to use the next size up. I use an 80cm here for 28.2e when I could use a 60cm and it means the signal never cuts out no matter the weather (google huricane bawbag) and I don't get moaned at.


I don't know what prices are like in Spain but I recall the large Channel Master (now Raven) dishes being two to three times the cost of prime focus metal dishes like the Famaval. I would be inclined to buy two big Famaval dishes if I was in Spain. With the mostly calm and dry climate of Spain I really don't see any point in getting a Channel Master dish except for professional use. Even if I did want a GRP dish a Laminas is cheaper and just as good.

Looking again at the Famaval catalogue I see the biggest offset they make is 130cm. All Laminas dishes are offset, but they are all GRP.


Sods law means once you put up two big dishes, the channels will be combined on one satellite. You sell your extra big dish at an annoyingly low price then six months later they split the wanted channels over two satellites 0.2 degrees apart again . . .

All in all its a kick up the Balearics.
 
Status
Not open for further replies.
Back
Top