Wavefrontier T90 project

[Lazarus]

Have you thought about a motor ?

 

[Captain Jack]

Here's your coat....

 

[hvdh]

I am rather annoyed that I cannot get 1w and 5e properly. Half the channels come in and half don't. These are not the strongest positions here anyway but Penta 85 has no problems with them (in focus). So on the edges, the T90 is equivalent to a 70cm dish-ish (on my setup anyway).

So... I can either bring the dish closer to the west to bring 1w and 5e more into focus but I will lose 39e - unless I extend the range with a bar of some sort. And potentially gain 5w?

How accurate is this site with its skew measurements? SatLex Digital :: Technology :: Calculators :: WF Toroidal Calculator

I find it strange 5°E and 1°W are so problematic. Are these so much weaker there than in NL?
While I had a T-90, it was centered at about 24°E. Had to extend the bar a bit for 1°W, yet that one still was strong enough.

The WF calculators are fine as a starting point only, while you are finetuning things will go "their own way".
Ignore LNB skew calculations, or how you would expect them to be for normal dishes. It's different for T-90 (or T-55).
Just optimise for best dB readings. In the end you'll see the skew across the bar varies much less than you'd expect.

P.S.: you have the little hole in the sub-reflector at the bottom, don't you?

 

[Archive4]

As stated in most other help threads, some pics may help!

I´ll get my t-shirt!

 

[timo_w2s]

I find it strange 5°E and 1°W are so problematic. Are these so much weaker there than in NL?

Yes, especially as you go further west. Signals on the east coast of the UK are strong for the Nordic beams but they start to drop off as you go west and CJ is quite far west.

 

[Captain Jack]

Yes, the sub reflector is the correct way around

Well, 5E is generally weak but Penta 85 was enough to get it even in the rain (unless it was particularly wet...). 1W is stronger generally but depends on transponder. The HD ones for Canal Digital were problematic even on the Penta. You'd need a decent 1m dish for that.

So the skew setting on the back of the dish. Is that literally just for the skew of the LNBs or is that also necessary for following the arc (I assume both). I set it up as follows:

1) Set skew on the back to 104 degrees as suggested by the site.
2) Place central LNB on '0' mark and align on 19.2e by adjusting elevation and the azimuth (around the pole).
3) Find other satellites by sliding the LNBs one the rail... 42e, which is 23 degrees off centre is coming in relatively strongly - about 12dB. 1w is 20 degrees off centre - probably too much for the fringe satellite...

Pics:

 

[hvdh]

Oh yes, many wrongs:
- The LNB clamps must be reversed on the rail, so that the LNB's are closer to the sub reflector.
- Leave 5 mm or so between clamp and LNB flange to start with (so the LNB get even closer to the sub reflector).
- You ignored setting the angle of the clamps according their position on the rail. So the outside LNB's look a bit more "towards the middle".
I'm sure much improvement is coming...

Edit: this pdf maybe helps as well. Ignore the remark about the pole being perfectly vertical, the adjustments will compensate deviations from vertical. They just want to sell angle meters as well...

 

[Lazarus]

Sounds like good, practical advice.

Looking forward to tomorrow's tweaking.

 

[Captain Jack]

I am glad there are many wrongs that you see! Means plenty of room for improvement!

Will reverse the clamps (it looked like it doesn't make much difference since the hole for the lnb clamp seemed in the middle).

I am not sure where you mean by leaving the 5mm gap - could you clarify please?

Yes, realised I should have rotated the lnb around the clamp... will do all this tomorrow

 

[hairybadger]

There is a small guide stencilled on the clamps so if you are eg 20 marks from centre it'll tell you at what horizontal angle to point it If you have the clamps the right way round, that is...

 

[hvdh]

About the holes of the clamps being in the middle (with respect to the rail, that is!) I'm not sure, since I have no T90 clamps now. For sure with the T55 clamp, the hole is NOT in the middle!
The 5 mm gap, is how you mounted the 19°E LNB for example.
But most important to have correct, is the angle of the clamp according rail position.

You can probably win an extra 1 dB or so by using IBU's instead of these cute baby-LNB's.

 

[4wd]

^^^

For sure with the T55 clamp, the hole is NOT in the middle!

Same with 90 clamp, towards the front.

Here's how it's here, presumably ok, holder angle screw towards lnb front, rail screw and angle readouts towards rear.

Had quite some headscratching with this at the beginning :O)

 

[Lazarus]

Great pic ...... says it all.

I'm finding all this very educational.

 

[Captain Jack]

Thanks chaps. This is all excellent info, much appreciated. Looks like I have to start at the beginning....

 

[Lazarus]

I'm greatly encouraged that you really are a true hobbyist, CJ.

Receive it, install it, scratch head, and only then .

"Are we human, or are we tinkerer?"

 

[4wd]

You can probably win an extra 1 dB or so by using IBU's instead of these cute baby-LNB's.

The cute's looks like max xo-11's ? They are very good imo.

 

[Archive4]

Looks like I have to start at the beginning....

Hands up all those expecting " abc " from the sound of music!

 

[Captain Jack]

Receive it, install it, scratch head, and only then .

All in the name of saving time. I mean, how hard is it to align a small ish fixed dish....

To be fair, the FM that came with the dish isn't great - clearly translated from another language (German probably). And the parts should have been designed to fit one way......

 

[Captain Jack]

The cute's looks like max xo-11's ? They are very good imo.

They are and the signal level wasn't really any different from an IBU. I like these and they look tidy.

 

[Archive4]

You could try a GI Twin on one of the weaker signals;)