Tweaking latitude has improved my signal

[dankargo]

Hi all,

I've had my 90cm motorised dish installed at my new property. The dish has had to be placed in a bit of an awkward location but the installer finally got there in the end. With my correct longitude and latitude in the receiver, I'm getting signal on all sats but I soon noticed the signal levels were slightly lower than what my 80cm dish had been receiving in my old property.

This afternoon I did as described on here and tweaked my longitude values to see if there would be much difference and there was minor improvement. However altering my latitude from 51.66 to around 70.00 and longitude from 0.030 E to 0.070W has dramatically improved reception. I know you aren't really supposed to mess with the latitude but in this case, it really has made a difference. I'm getting 80% on the Nordic beam on 1W (was 60% before), 67-70% on the TRT channels on 7E (was 49-55 previously), 99% on many Hotbird TPs (was maxing out at 89% previously) and even pulling in lots of feeds now.

After altering the latitude, I did a 'Go to 0' and drove the dish across the arc, thankfully its still hitting every single satellite but with improved signal across the board. I know the dish probably wasn't installed as accurately as it should have been but this fix alteration seems to have fine tuned everything. Just wondered if anyone else has had to alter their latitude values to peak signal levels?

 

[Lazarus]

Hmm. I suspect by far the predominant factor was the 0.6 degree Longitude error.

If you now return the Latitude figure to something rather closer to the actualité, you should find all remains well.

All you're doing by changing that is to alter slightly the algorithm USALS uses to determine how far to pan when changing Satellites.

 

[Channel Hopper]

Moving the dish size up by 10cms all round means an increase of upwards of 20% in area and an equivalent reduction of the beamwidth . Correcting latitude will have much more of an effect on the resultant signal when the larger dish is not seeing the Clarke belt.

 

[a33]

Latitude difference from 52 to 70 means the usals calculation for an angle of 60 degrees away from due south (do you get signal that far?), differs about two degrees hour angle.
For satellites nearer due south, the hour angle difference is smaller.
So if the 70 LAT works best for you, when you are at 51.66, the motor setup is not ideal, to put it mildly.

A USALS coordinate alteration is not a real finetuning, it is just an adaptation to a not perfectly set-up motor.

That being said, USALS algorithm seems to calculate from 'traditional' motor setup angles (axis parallel to earth rotation axis).
I believe the USALS algorithm gives better results when you use the 'modified' latitude value of the modified motor angles (using forward tilt of the axis, so a latitude some tenths of a degree higher) as input value for the USALS calculation. I've not calculated this through, though, yet, if this is enough for optimal correction of the USALS outcome.

But in your case: 0.6 of a degree is not the same as 18 degrees, though.....

Greetz,
A33

 

[dankargo]

Latitude difference from 52 to 70 means the usals calculation for an angle of 60 degrees away from due south (do you get signal that far?), differs about two degrees hour angle.

You are spot on actually, I've just tried scanning the sats furthest east and west and signal levels are pretty poor. On 42E, the TRT channels are coming in 60-63% but some of the weaker TPs are now no longer receivable. I know for a fact if I put my latitude values back to what they should be, I'll get better signal levels but as soon as I move back to satellites closer to south, they'll take a hit in signal levels.

Something obviously not right in the setup but given the dish is so high up, It's not something I can get to easily. I'll eventually get it sorted but for now, I think I'll have to make the best of what I have which means keeping the latitude +18 degrees what it should be. I very rarely go to 42E, perhaps only for TRT 4K which thankfully is on a strong TP that I can still receive at about 63% SNR. The majority of the time I'm usually between 5W - 19.2E, with a significant interest in 7E & 10E for feeds - picking up a lot of them with the incorrect latitude/longitude values but they take a significant drop/lose lock completely if I put in the correct figures.

 

[Mickha]

You might be better off ignoring your Latitude, and Longitude, if your dish is that far off, which I doubt, as your dish is tracking the satellite arc, picking up both your furthest East, and West satellites, as your satellite setup describes getting 62E - 45W, and switch to Diseqc 1.2.
Using Diseqc 1.2 allows you to manually store your satellite positions, at their peak levels, but you have to use your receiver to set it up, manually, but once set up it works exactly the same a Usals, thus by selecting a channel, stored on a different satellite, the dish will automatically move to it.
It should only take a little time, and patience, to get the maximum available signal quality from all your satellites.

 

[dankargo]

You might be better off ignoring your Latitude, and Longitude, if your dish is that far off, which I doubt, as your dish is tracking the satellite arc, picking up both your furthest East, and West satellites, as your satellite setup describes getting 62E - 45W, and switch to Diseqc 1.2.
Using Diseqc 1.2 allows you to manually store your satellite positions, at their peak levels, but you have to use your receiver to set it up, manually, but once set up it works exactly the same a Usals, thus by selecting a channel, stored on a different satellite, the dish will automatically move to it.
It should only take a little time, and patience, to get the maximum available signal quality from all your satellites.

That actually sounds ideal. Are there any guides available on how to set up Diseqc 1.2? I've always relied on USALS so this would be a bit of a learning curve. Would I start at the satellites furthest east and west and make my way back to the satellites closest south, or start nearer due south?

 

[Channel Hopper]

I would invest the time in a 30 minute visit from a local installer that knows what he is doing, it sounds like there is an issue with the declination of the dish on the mount (and possibly the north south alignment) that the last one couldn't understand.

 

[Mickha]

That actually sounds ideal. Are there any guides available on how to set up Diseqc 1.2? I've always relied on USALS so this would be a bit of a learning curve. Would I start at the satellites furthest east and west and make my way back to the satellites closest south, or start nearer due south?

You can start at any satellite, it's not that difficult, you just use your tuner options to set it from Usals to Diseqc 1.2, then find, and store, each satellite, on a different number.
If you post your receivers make, and model number, someone should know the menu structure, or find it on the internet, unless you can post images.