Nearer to textbook, my Gibertini 1.5

[archive10]

Congrats on the tweak, as John says always satisfying to get a little more out of the system.

Once I had the dish face pointing at the right angle I needed to line the lnb up, as using the proper lnb holder, held the lnb in the wrong angle.

So after I had looked through one of my sheds I found one of my iss lnb holders.

Had to bolt it to the underside of the lnb arm to get a signal, see below.

What prompted you to suspect the LNB was held in wrong location?
And if you were using the official holder previously, how much off is the LNB position of that?

 

[John]

Congrats on the tweak, as John says always satisfying to get a little more out of the system.

What prompted you to suspect the LNB was held in wrong location?
And if you were using the official holder previously, how much off is the LNB position of that?

Following on from st1, i suspect you can get a bit more out of it.
I took another look at the lnb holder you have in the previous posts and compared it to a web stock photo of the same dish and supplied lnb holder.
Your new holder looks to be positioned wrong , it looks to be aiming low and sitting too low to the support arm. Looking at the stock photo and enlarge a bit to see the lnb holder a bit better you can see what i mean, if you photo shop your lnb position over the stock pic it becomes more obvious. I know the dish in the pic is only roughly put together for demonstration purposes but it won't be far off. I could be wrong and it might just be an optical illusion ? .... what do you think Chris
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[Archive-8]

@st1 the main reason woot tweeking was simply the numbers, I get a bit ocd with numbers.

I have never been able to get the dish face to read 10.3° with the original holder. The dish was always 11.4°.

@John yes with the original holder I need the dish face on 11.4° still way out.

This kept bugging me, and following on with a conversation with @RimaNTSS last year, I know the lnb is also not in phase.

I grabbed the iss holder as it was the closest to what I needed at the time.

Now I have a very good place to start, but feeling happier with the numbers now :-)

Just as a side note my op125 and original holder hits the mark every time @ 10.3°

 

[Captain Jack]

26e... You're getting some West African transponders like 12303H. No sign of 12284 for MBC?

36e - you should easily get 12245H on sub Saharan beam. Maybe the BS just missed it.

 

[RimaNTSS]

@Chris1979 , I would suggest to lean your dish exactly 11.4° , and then adjust height if the LNB little by little to get maximum signal level. Of course, LNB should be always pointed to the proper aiming point, and this point on the offset dish is always below the center of the dish. For LNB holder I would suggest very simple but effective solution, something like I showed in this thread.

 

[Archive-8]

26e... You're getting some West African transponders like 12303H. No sign of 12284 for MBC?

36e - you should easily get 12245H on sub Saharan beam. Maybe the BS just missed it.

26.0°E dr hd has the mbc on 12284 v 27500 7.8db

I have 217 TV channels and 113 radio.

 

[John]

.... I'm not the greatest at pc graphics but here's another comparison of yours alongside the stock photo. Iv'e flipped your image around. See the angle differences and also how the lnb is sitting lower to the support arm on yours. Sort it out tomorrow before it rains lol.
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[Archive-8]

If I optimism the dish for mbc 12284 v 27500 then the transponder 12303 h 27500 has a flashing signal bar.

I need to move the dish east a few clicks to optimise 12303.

 

[Archive-8]

26.0°E 12303 H 27500

 

[moonbase]

31.5°W Dr HD D15 locks 2 transponders, pc only shows one.
View attachment 105836 View attachment 105837

@Chris1979

I tested the scan with EBS Pro and the TBS blind scan software on 31.5W to see if I got any gaps in the transponders found. Both EBS Pro and TBS blind scan picked up the usual 3 Ku band transponders. I have attached the scan images below. The scans were done using a Precision 1.5m prime focus dish with Inverto C120 quad output LNB and a TBS6925 card.






Rgds

 

[Archive-8]

@Chris1979

I tested the scan with EBS Pro and the TBS blind scan software on 31.5W to see if I got any gaps in the transponders found. Both EBS Pro and TBS blind scan picked up the usual 3 Ku band transponders. I have attached the scan images below. The scans were done using a Precision 1.5m prime focus dish with Inverto C120 quad output LNB and a TBS6925 card.

View attachment 105877

View attachment 105878


Rgds

When I did the scan it looks like I had it on 4mhz steps.

I still need to do so tweeking, so I can get my numbers spot on.

What steps did you set to scan 31.5?

 

[moonbase]

When I did the scan it looks like I had it on 4mhz steps.

I still need to do so tweeking, so I can get my numbers spot on.

What steps did you set to scan 31.5?

Chris,

For EBS Pro I used 2MHz steps, for TSB Blind Scan there is no option to select the step size and it does not indicate what it is. There might be an "*.ini" file somewhere that controls it?
As pointed out by previous posters, I think the LNB is the variable that will get results for you.

The dish I used is similar size (1.5m) to your Gibertini. However, with a Precision prime focus dish, if the matched feed support arms and Ku feed are used then by default the C120 LNB is automatically located to the correct focal length and pointing accurately. With the offset dishes there is a lot more flexibility in location of the LNB and its angles.

It might be interesting to see what results you get from 31.5W using 2MHz steps? I have noticed in the past that the Ku signals from this satellite seem to vary with time of day, there might be a time of maximum output?

Rgds

 

[Archive-8]

Bit later on I will go and tweek the polarmount down to 38.4° and the dish face to 10.3° and tweek the lnb.

It's all still work in progress

 

[moonbase]

Bit later on I will go and tweek the polarmount down to 38.4° and the dish face to 10.3° and tweek the lnb.
It's all still work in progress

Chris,

I used a similar method to yours to align my dish on the arc. However, one thing I did notice was that the theoretical elevation angle did not give the best result. I found that the theoretical angle was close to maximum signal level but was a couple of tenths of a degree off the maximum. I put this down to a slight deviation of the dish parabolic shape from perfect symmetry.

What I did was to use a meter and increased the elevation angle to the point where the signal dropped to around 70% and made a note of the angle on the digital inclinometer. I then decreased the elevation angle so it went through the maximum point and came out on the other side with signal level of around 70%. I then made a note of this elevation angle and set the dish at the mid point of the two angles. I then introduced the declination offset angle to its theoretical value and re-adjusted the elevation back up to maximum signal level.


Rgds

 

[Archive-8]

What I did was to use a meter and increased the elevation angle to the point where the signal dropped to around 70% and made a note of the angle on the digital inclinometer. I then decreased the elevation angle so it went through the maximum point and came out on the other side with signal level of around 70%. I then made a note of this elevation angle and set the dish at the mid point of the two angles and finally set the declination offset angle to its theoretical value.

Might give that a try later, I never thought of that.

Now the old gray cells are working overtime

 

[Archive-8]

going out to play

 

[moonbase]

going out to play

Good luck, I hope you find a few more db, every little helps.

I forgot to say earlier that when I did the elevation angle measurements at approx 70% signal level above and below the elevation level of maximum signal I found that it was approximately a 2.0 degree range on my Precision dish. I think I also did a similar test at 80% signal level and found the range to be around 1.0 degrees.

I also backed off or completely removed the declination offset angle for the elevation angle test. It was only after I had the dish set at the mid point of the upper and lower elevation angles that I put back in the theoretical declination offset angle


Rgds

 

[Archive-8]

Got the polar mount spot on 38.4°

 

[Archive-8]

Got the dish face on 10.3° for 1°W

 

[Archive-8]

Turned the lnb arm 180° just to try it



On 1°w it added up to 5db on some transponders.