Help SNR 19% - 24%

[rob_smith01]

Hi Folks

I wonder if anyone can help me.

Having setup my dish acording to various guides etc I feel my motorised setup is "true" bracket plump and angles on motor and bracket correct etc.

The issues Im having is having pointed the dish south and moved to 0.8 west to fine tune to arc. Im getting low SNR issues. No matter how much I finely tune or move the dish the best I can get from the strongest transponder is 24%. Similarly no matter which bird I point to the same SNR range occurs flickering from 19-24%. I have checked various things so far; including re doing all the F-connectors carefully incase one is fowled. I have taken off the arm to check the LNB is a) not damaged or b) misfitted. Unpluggining all cables gives a 3% SNR so theres obviously a signal coming from somewhere on the dish. Again all these dont seem to be the cause as the same signal strength occurs. The only thing I can think it can be is the LNB and Im will be testing this with a sat meter this week to confirm or deny.

If anyone has any thoughts it would be of great help as I can think what else it can be at this stage.

 

[Lazarus]

First of all, some details of Dish and LNB would help.

Secondly, some Piccies would help even more!

 

[rob_smith01]

I havent any pics for the time being I will take some tonight. Reciever is a TM500 Super latest UR image, the LNB is a Icecrypt single unversal 0.1db, dish is 80cm with IceCrypt DM-101 DiSEqC H-H Motor

 

[Lazarus]

Ah, Icecrypt .................... Your problem may well be skew related as some of those LNBs have been constructed with the wrong "Zero Skew " Datum.

See http://www.satellites.co.uk/forums/...tar-lnb-fskuvn-icecrypt-0-1db-single-lnb.html

Pretty sure this is your problem - and easily sorted out

 

[rob_smith01]

Hi matey

Just a bit confused by what your saying,

Iam assuming that what you are saying is these LMBs could \ have been manufactured slightly wrongly and the zero skew on the unit isnt correct or in the usuual position. And to offset this problem I need to skew the LNB to the "actual" zero position.

My setup is a motorised setup and the dish is pointing 0.8 W at the moment (for the initial setup). Im thinking the skew on the LNB should be at 0 with this position and the LNB level iam assuming (if what iam assuming your saying is correct I have to alter this). As the motor turns to a sat it skews the dish and LNB it for you.

 

[Lazarus]

Yes, the LNB should be set at zero skew for your South Satellite and thereafter the motor locus corrects skew automatically ................. BUT we all assume zero skew is when the F connector is at bottom dead centre: In the case of some Icecrypt and some Fortec Star LNBs this is NOT the case and zero skew occurs with the F connector at an unexpected position (Read the link provided earlier for precise details).

So, what you need to do is set the motor back to Thor, then rotate the LNB to achieve the correct zero skew attitude, rather than the assumed one.

The differential between the correct and assumed (or "natural") position is sufficient to be the cause of exactly the results you report as neither polarity is being optimally received.

I believe the zero skew position actually occurs when the F connector is at about 4 o'clock (as viewed looking from LNB towards dish). It may look odd once corrected, but should be perfectly fine.

 

[PaulR]

Iam assuming that what you are saying is these LMBs could \ have been manufactured slightly wrongly and the zero skew on the unit isnt correct or in the usuual position. And to offset this problem I need to skew the LNB to the "actual" zero position

Yes. Instead of being vertically aligned when pointing due south the LNB has to be skewed (rotated in its housing).

Im thinking the skew on the LNB should be at 0 with this position and the LNB level iam assuming (if what iam assuming your saying is correct I have to alter this). As the motor turns to a sat it skews the dish and LNB it for you.

Yes, as the dish follows the arc of satellites in the sky the mounting will rotate the whole dish as required.

 

[rob_smith01]

Many many thanks guys I shall be up the ladder agian tonight in the dark and cold hopfully for the last time shoudl this solve the issue.

 

[rob_smith01]

Hi folks,

having tried squewing the lnb a few times tonight, im afriad nothing is changing, Its back to the drawing board for me. Ive a sat meter coming this week so at least I can test if the lnb isnt faulty.....

 

[Lazarus]

Sorry to hear the apparently obvious problem wasn't the key to your woes.

To go right back to the beginning, are the low Quality readings associated with failure to lock or pixellation .................. or could it just be dodgy metering?

ie Is it actually a real problem or one of perception?


If it is a "real" problem ie you don't get any Video/Audio, then it could be there is a fundamental issue with your interpretation of the alignment procedure ie You may be getting the quiescent readings that occur purely as a result of an LNB being connected ................... which is where piccies come in handy, 'cos chaps can spot things that no amount of words could bring to light.

Viz: Your Motor should be set to somewhere in the mid 50s against the Latitude scale (ignore the Motor's Elevation scale) and the dish bracket should be set to approx. 24, the effect being to leave the dish face slightly above vertical when pointing at Thor.

 

[rob_smith01]

Hi Tivu

Many thanks for the advice again.....you will have to bear with me as Iam a noob still on a learning mission

The low readins are failure to lock, I cant seem to get close to a signal frm thor (or indeed an sat) no matter where I move the dish to. The Lat on the motor is set to 53 as is my actually latitude. and my dish bracket is a little loose at the moment so i can adjust it but I have it set to 24 and a bit (should be 24.4 I think). I shal take pics tonight with the slr camera to try and give you guys a better idea.

One question though; Would the SNR change at all if i moved the dish finely or massievly? as no matter where i point it or make either a fine or big adjustenmt with the dish to a sat the readings at the moment dont seem to move out of the 19-24% scope? I would have expected to see some sort of fluctuation up in say the 40s down to the 20s at least. Anyway it could be that im missing a sat meter really or something. The one thing I would say if I disconnect the LNB the SNR drops to a rock steady 3% (background signal interference I am assuming) which I would expect. So all I can assume the LNB is recieving something.....

 

[Lazarus]

With an LNB connected but dish misaligned, you will get a characteristic quiescent reading for Strength and often for Quality too. But they mean nothing other than that the system is acknowledging that there is a powered up LNB present.

The value in either of those readings comes only when you are very close indeed to a Satellite position and then they will change ............. it is that change which you seek and it will be significant. Once the Strength upswing is noted, then you optimise for best Quality reading.

Your symptoms as clarified suggest you haven't yet achieved any form of effective alignment: "Loose" is not good, either!

As for Elevation, that needs to be changed too, not just the azimuth: Essentially you are doing the same as if aligning a single fixed dish, except that azimuth is achieved by rotating the motor/dish assembly as one. Elevation is achieved by adjusting the dish bracket only.

There is no merit in trying to set it to 24.4 against the scale as however plumb you think your mount is, there will be a fractional error and there will also be mechanical errors elsewhere - adjusting the bracket empirically accounts for all these inevitable errors.

Finally, both azimuth and elevation need to be deadly accurate as anything more than a couple of tenths (particularly in elevation) translates, over 24000 miles, to a big miss!

 

[sonnetpete]

Can I come in on this as a fresh 'head' so to speak?

I have to assume that you've checked your mount for 'plumbness' with the motor/dish assembly attached and that you've inputted your lat and long coordinates into the motor setup section of your receiver.

Yes, if you move the dish slightly away from your target sat the readings will drop away. I'm a little confused, so can you confirm that you are getting up to 24% QUALITY readings and not just STRENGTH?

The dish setting is correct but dish elevation scales are often inaccurate so you have to adjust to best results. I've only ever used a needle and tone meter to help with alignment, right up to my current dish. Check that you have in fact you have assembled the dish correctly and not mounted the bracket upside down (the one that joins the dish to the motor stub).

I also note you are using an image on your receiver. I'd just check that this isn't causing a problem, is it possible to go back to the receiver basic software till you get it set up and then re load the image?

Pictures would definitely help us eliminate obvious problems. Hope my input helps.

 

[rob_smith01]

It sounds more like an alignment issues then, possibly ive missed something, will get the camera out tonight as well. I have a sat meter coming so maybe this will help me. Next step I will firstly double check the motor lat is on 53 for my sanity, then tightenup the dish bracket to 24 get the meter set up and see what I can achieve on 0.8w with the fine movement. Maybe my big floor was expecting I could do it using readings on the reciever and I actually really need a meter to aid me. I have noticed many people have just taken a rough guess and then finely tuned using their recievers, a wrong assumption maybe.

 

[Lazarus]

Can be done with some receivers, but often the "metering" is vague and slow to respond.

One of my receivers is the cheapie SL65 from Lidl and that has an audio tone built in, so I wang it through a 75W Hi-Fi Amp and can hear it outside where the dish is!

As regards Motor setting, do satisfy yourself you've set 53 against the correct scale ............. one side of the bracket will be directly calibrated in Latitude and the other with a corresponding (but, in practice, not useful) elevation figure.

 

[PaulR]

I have noticed many people have just taken a rough guess and then finely tuned using their recievers, a wrong assumption maybe.

Strange as it may seem, the larger the dish the more difficult it is to find your first sniff of signal. A smallish (50cm - 60cm) can be set up on a strong satellite using figures and there's a fair chance that it'll be close enough to be able to home in exactly as you thought. 80cm isn't very large as they go but for a newbie it could be just lack of familiarity you're suffering from.

 

[rob_smith01]

Can I come in on this as a fresh 'head' so to speak?

I have to assume that you've checked your mount for 'plumbness' with the motor/dish assembly attached and that you've inputted your lat and long coordinates into the motor setup section of your receiver.

I shall check the plumbness again with the dish attached, and yes the lat an longs are in the settings on the receiver for the motor

Yes, if you move the dish slightly away from your target sat the readings will drop away. I'm a little confused, so can you confirm that you are getting up to 24% QUALITY readings and not just STRENGTH?

A: The readings iam seeing are SNR 19-24%, ACG 0 (on thor 6).

The dish setting is correct but dish elevation scales are often inaccurate so you have to adjust to best results. I've only ever used a needle and tone meter to help with alignment, right up to my current dish. Check that you have in fact you have assembled the dish correctly and not mounted the bracket upside down (the one that joins the dish to the motor stub).

A: Ive a meter n the way just incase and I shall check the bracket as thats one thing i havent double checked.

I also note you are using an image on your receiver. I'd just check that this isn't causing a problem, is it possible to go back to the receiver basic software till you get it set up and then re load the image?

A: I doubt its the image as it works fine on the legacy fixed sky dish I have on the house pointng obviously at 28.2 and receiveing all FTA stuff fine.

Pictures would definitely help us eliminate obvious problems. Hope my input helps.

A: I will get some together asap so you can cast your eye over my potential mistakes...


many thanks any help is much appricated

 

[rob_smith01]

Hi folks took some picies, bear in mind ive "un tidied" the cabling and removed the amalg tape whilst ive been tinkering with fixing this issue.....

 

[Lazarus]

Well, give or take parallax and perspective factors, there don't seem to be any howlers.

Attitude of dish looks correct .............. I think the consensus, after the side alley about the Icecrypt LNB, is that you simply haven't struck lucky with the precision required for alignment.

 

[sonnetpete]

I can't see any obvious problems either. It may make it easier initially to align on a stronger satellite, say 19.2°E. So drive your motor and dish to that position, (assuming you are using USALS) choose an active transponder and align as you've done before for Thor. If you can't hit something from that bird there's something other than alignment at fault. Even if you get some transmissions and they don't seem right, get back to us, tell us which channels they are and we can deduce which way your aligning needs to go. If you do get the correct bird and a decent signal, peak it up and go back to Thor to fine adjust. I can only repeat that it is VERY slight adjustments we talk about when trying to receive a satellite transmission.