Channel Master 1.8m with new Feedhorn WORSE!

[robt23]

Astra 1 is 19.2 * so if you only the dish strait at the angle of 0 * and turn to 19.2 * and the lnb you have a mismach an less signal

Only if you return the dish+lnb to 19.2 * and the lnb is strait ( 0 * skew in the dish) then you have max signal and no fase signal tordation..

What you are actually saying is that the whole set-up has to be orientated 19.2 deg and of course keeping the lnb at 0 deg just like a motorized dish.

The tricky part is how to apply this method to a fixed dish ?

We might be able to squeeze the 2f at 28.2 deg even more.

Your youtube videos show this well.

Thank you for this information.

 

[Huevos]

W

The tricky part is how to apply this method to a fixed dish ?

Don't bother. It's a lot of nonsense. If you are having trouble visualizing it just think of a PF dish. Skewing the dish, more or less, does nothing whatsoever to signal capture, and certainly not polarization. An offset dish is just the same. Only skewing the LNB has any affect on polarization.

 

[robt23]

If Phoenixx is saying that the whole dish and lnb must be at the same deg i.e. start with both your dish and lnb at 0 deg , then rotate to 19 or 28 deg whatever to get full signal ;

Wouldn`t that effect be gained by a normal prime focus where both dish and lnb are in line , focused on the satellite !

Should we be installing prime focus dishes to get the best signal ? a thought......

 

[Huevos]

If Phoenixx is saying that the whole dish and lnb must be at the same deg i.e. start with both your dish and lnb at 0 deg , then rotate to 19 or 28 deg whatever to get full signal ;

Wouldn`t that effect be gained by a normal prime focus where both dish and lnb are in line , focused on the satellite !

Should we be installing prime focus dishes to get the best signal ? a thought......

That is not what he is saying. He is saying that the LNB should be at 0º when the dish is facing due south and then rotated around the polar axis (so the dish is raked over) until it is aligned to the satellite. This is definitely wrong with Astra satellites due to the pre-skew, i.e. when the electrical vector of Astra satellites is horizontally polarized that polarization is not parallel with the equator. Also moving an offset dish around a polar mount does not in any way give it better efficiency or capture area compared to an az/el mount on a fixed vertical pole.

 

[radicaldoc]

I have an offset channel master that is simple to set up i don't think we need to go to the trouble of changing to a prime focus for astra. And i doubt very much it would produce any better quality of signal with the same size dish.At the moment all is reasonable i still have to find an old c120 flange to experiment with. but most of the time it is OK the only problems i get now are loosing signal at certain times of the day all ways same time's of the day. I suppose this is the winter arc of the satellites ..

 

[Huevos]

I don't think we need to go to the trouble of changing to a prime focus for astra.

No one said you did.

 

[radicaldoc]

Radical, don't think that your posts are not appreciated. To be honest, I was confused about how the LNB comparison chart was presented. It just mentions H/V with no frequencies. And all H lines have a quality of 100.

I found Black Ultra to be the best LNB in my many tests across many dishes. Granted, none were on the 1.8m (I think a feedhorn + C120 LNB is better here but opinion varies), on various 80cm, 1m and 1.2m dishes, the BU LNB outperformed all of the competition. I even had one converted for me so I could use it on my Fibo, which only accepts C120 LNBs - http://www.satellites.co.uk/forums/topic/155379-project-fibo/page-5#entry830873

Not only does it fit straight on the dish, but skew and depth are easily adjustable.

No idea why a BU is such a good LNB, but it just is.

Hi Sleepy i am going to try the BU mod in the next few days. am i right to assume (doubt it LOL) that when you cut and shut the C120 flange on to my BU that the important length is of course the feedhorn it's self. And that the the length of the cut and shut isn't going to make a whole lot of difference as long as the feedhorn is right.there is no exact size to make the length of the C120 LNB input????
Cheers...

That sounds as clear as mud....... :-beer

 

[Captain Jack]

Hi Sleepy i am going to try the BU mod in the next few days. am i right to assume (doubt it LOL) that when you cut and shut the C120 flange on to my BU that the important length is of course the feedhorn it's self. And that the the length of the cut and shut isn't going to make a whole lot of difference as long as the feedhorn is right.there is no exact size to make the length of the C120 LNB input????

That's the theory. In practice, I found that I had to move the BU inside the modded flange to adjust the focal point for the best signal.

 

[radicaldoc]

So if i keep the BU neck the same length it should be around about?? Thanks for the help.

 

[Captain Jack]

About right, yes. But try to make it adjustable in any case.

 

[radicaldoc]

About right, yes. But try to make it adjustable in any case.

OK thanks Bud i will let you know how i go on...... :-beer

 

[radicaldoc]

Well Got the C120 Feedhorn i am going to use to convert the BU it is a Invacom. But just looking at it what good is this as a feedhorn then the feed is supposed to Collect and direct signal to the LNB yes? but if like this one the only way down to the Lnb is in the centre hole what is the point of this then even if it collected signal all it will do i bounce out again won't it?? Or am i not seeing it ??????

 

[Waveguide]

In laymans terms the feedhorn is like a zoom lens on the LNB.
When the feedhorn is properly adjusted the LNB will only see the dish and
not what is on the side of and behind the dish. Any extra unwanted noise will be
avoided this way. Signal quality will be slightly improved.

Some more detailed explanations here:
http://www.globalinvacom.com/main/support_dbs.php

 

[Huevos]

Well Got the C120 Feedhorn i am going to use to convert the BU it is a Invacom.

Completely wasting your time with that feedhorn. It is for a PF dish.

 

[radicaldoc]

Completely wasting your time with that feedhorn. It is for a PF dish.

I don't think so....!!!!
I am using the flange not the feedhorn so how is that wasting my time?????
My attempt all done now given the weather i will give it a try tomorrow although looking a bit doubtful.....

 

[radicaldoc]

In laymans terms the feedhorn is like a zoom lens on the LNB. When the feedhorn is properly adjusted the LNB will only see the dish and not what is on the side of and behind the dish. Any extra unwanted noise will be avoided this way. Signal quality will be slightly improved. Some more detailed explanations here: http://www.globalinvacom.com/main/support_dbs.php

But is the focal spot this small that centre hole is 2cm and if it is then why put on the large round part if you are not going to collect any other signal?? As i as i said if you were using it to collect signal fair enough but this isn't going to collect anything so what's the point of it???

 

[Waveguide]

You don't beleive the explanation in the link to Invacom?

Another point for using the plate with the concentric rings is that spiders will be confused in the maze and won't be able to build nests in your LNB.

 

[radicaldoc]

As i have been ill with bronchial pneumonia for 4 weeks i haven't been able to test this properly but i put it on for a quick look and it showed signal strength increase on my meter and my humax. Unfortunately I need to check dish again now as while i have been ill we have had horrendous storm and very very high winds. So at the moment i am experiencing odd problems I now loose the new channels between 12-1 o'clock and 7 O'clock at night then they come back solid as rock till 10 o'clock - around 11 o'clock and then back again. I am hoping it is a mixture of time of year and the dish possible slightly out now after storms. I can only hope. Iwill check when weather changes a little and it is fit to venture out an mess with the set up again..

 

[robt23]

I have been ill with bronchial pneumonia for 4 weeks i haven't been able to test this properly.

Get better in your own time radical , i had it once - not nice.

Once better let`s hope your tests show hope......

 

[sydeccles]

First off: I am NOT an installer or any types of Satellite specialist, however after reading this thread I thought I would add my 2-penneth.

I currently have 2 dishes in Spain (20 minutes south of Alicante) One dish being a Famaval 1.8 that I have been using for 5 years or so, the other is a Channel Master 1.8 offset. (this being my new toy) yes I know boys and their toys!!!

First off I used an Invacom quad and a Channel master LNB with the correct plastic fittings to reduce the LNB mount to C120 size, this does not permit any focal length adjustment, only rotational / skew angle.

Second I used an Inverto Black Ultra (with built in feed horn) this LNB does permit adjustment of focal length as well as Skew.

I have a Horizon USB meter and obtainded the following readings ...I found that the Inverto gives more Signal strength but less quality.