Is this focal theory right or not?

[SEOShamsher]

Hi all, quick question just to check my thinking.


If I first align the dish purely based on angles (azimuth + elevation) as accurately as possible without using signal, so it’s theoretically pointing exactly at the satellite, does that mean the whole dish surface is correctly aligned?

Its Prodelin 1.8m offset fiber dish 179-189 numebrs marking on back

Then after that, I connect the LNB/receiver and only adjust the LNB position (forward/back) to find the true focal point and maximise signal, without touching the dish again.


In other words, is it valid to separate it like:

1. get dish pointing “perfect” geometrically
2. then do all optimisation via focal adjustment only

Or in reality do you always end up mixing both (dish + LNB tweaks) even if your initial alignment is very precise?

 

[Channel Hopper]

Are you fabricating feed arms or are they originals with the Prodelin (TPG) markings ?

 

[SEOShamsher]

I'm not fabricating from scracth rather than using previous dish owner made arms which are very closed to that everyone using as shown below image.

just want to try if i can improve further. Below is closely similar to mine which i can adjust further if i want.

 

[Channel Hopper]

I'm not fabricating from scracth rather than using previous dish owner made arms which are very closed to that everyone using as shown below imageView attachment 168592.

just want to try if i can improve further. Below is closely similar to mine which i can adjust further if i want.

That is not a 1.8m dish, nor feed/arms from Prodelin.

 

[SEOShamsher]

I've seen other people cutting throat and fixing regular universal LNB to this scaler ring.

I talk to one guy and he told scaler ring only help if focal is not accurate so it help to adjust focal.

there are two size available here.

 

[SEOShamsher]

That is not a 1.8m dish, nor feed/arms from Prodelin.

feed/arms from Prodelin.

yes right these arms are diy. but dish is from Prodelin. and size is 180 x 193 cm . i did measure it. there is marking as well on back that say 179 189 and these dishes are from satellite internet Vsat vendors.


only reflector is original and rest of it DIY.

 

[RimaNTSS]

Adjusting elevation of any antenna is possible with a great precision to the fraction of degree. But azimuth is not easy at all. The proper way how to adjust this nice 1.8m Prodelin is to properly install the LNB to exact calculated position and then by moving antenna catch signals from desired satellite. Offset angle of this dish is 22.3*. Some time ago I had 2 such dishes.

 

[SEOShamsher]

if you have original focal point details please share.

 

[Channel Hopper]

I've seen other people cutting throat and fixing regular universal LNB to this scaler ring.

I talk to one guy and he told scaler ring only help if focal is not accurate so it help to adjust focal.

there are two size available here. View attachment 168595View attachment 168596

View attachment 168597

View attachment 168598

Not compatible feeds either (you have the specifications somewhere ?)

 

[SEOShamsher]

maybe because specialize feedhorns and LNBs not available in india that's why.

what do you suggest please guide me in right direction to get most out of this.

 

[SEOShamsher]

Not compatible feeds either (you have the specifications somewhere ?)

specification for dish or focal point or scaler ring feedhorn?

 

[Channel Hopper]

maybe because specialize feedhorns and LNBs not available in india that's why.

what do you suggest please guide me in right direction to get most out of this.

Why ?

In this part of the world there are similar questions from idiots, with reflectors but no feeds/feedarms.

 

[SEOShamsher]

Why ?

In this part of the world there are similar questions from idiots, with reflectors but no feeds/feedarms.

I understand. My reflector is Prodelin 1.8m offset, but feed arms are DIY. I want to optimise performance. should I stick with standard Ku LNB or is there a better matched feed option for this f/D?

 

[RimaNTSS]

if you have original focal point details please share.

Sure I have. There you go

 

[Channel Hopper]

I understand. My reflector is Prodelin 1.8m offset, but feed arms are DIY. I want to optimise performance. should I stick with standard Ku LNB or is there a better matched feed option for this f/D?

Prodelin (or at least the parent company) has multiple feeds (and feed arms) available for their antennas. The issue will be getting an order large enough for the maunfacture and shipping to be acceptable.

What is unlikely to be suitable is the aperture of the average LNBF to optimise the signal, regardless of how well it is placed at the focal point.

 

[SEOShamsher]

Sure I have. There you go View attachment 168600

Thanks, this going to be really helpful. I'll try this and post results here soon.

 

[SEOShamsher]

Sure I have. There you go View attachment 168600

one mor thing. the measurements are not from clamp center rather than its from clamp right side if i stand in front of dish not back. just confirming if image is not flipped

 

[RimaNTSS]

the measurements are not from clamp center

The measurements are from antenna's focal point. F is usually about 2 cm in front of the middle of the clamp. Your task is to co-locate feed's phase center with the focal point of antenna, at the same time the feed should be pointed to the proper point in surface of dish.

 

[a33]

should I stick with standard Ku LNB or is there a better matched feed option for this f/D?

Given the specs by @RimaNTSS , f/D of this offset dish is about 0.60 - 0.61, so in the normal range for an offset dish LNB I would say.

F is usually about 2 cm in front of the middle of the clamp.

Is this your experience? I've often read on the dutch forum it is about 3 - 3.5 cm in front of the middle of the clamp. But I guess I only checked this once on my Triax TD115, I must confess, so I don't speak out of experience.

greetz,
A33

 

[RimaNTSS]

I've often read on the dutch forum it is about 3 - 3.5 cm in front of the middle of the clamp

Yes, could be 3-3.5. But taking in account the answer from INVERTO company, that the Phase Center is located 5mm behind the cap, which looks like about 20mm from the edge of the holder. In fact, the right distance is very easy to adjust by the maximum signal from the satellite.