6 Foot Solid Prime Focus Ku Conversion

[Lone Gunman]

DMSI Lawsuit? Nope... as supported by this post by WSI: http://www.satelliteguys.us/xen/posts/3110891/

Don't know how I missed that when it was originally posted but I guess that explains what was really going on with the law suite stuff. Thanks for the link!

 

[Jason S]

If the op doesnt want to spend too much $$$, how about the GEOSATpro SL1P for $18?

That is probably a good idea, I can use the SL1P in a comparison study with the Frankenstein model above.
If the Frankenstein is close I will use it, but if the signal levels are extremely subpar, I will be placing an order from Europe.
(A good chance I will order from Europe either way just to have parts.)

This is a neat project to follow.

Hopefully I don't divert the thread too much, but I have a rather basic question about the SL1P...

Looking at the SL1P photos, it appears that it has somewhat of a small scalar built in to the body. It also appears to be too large to slip into the scalars that I've seen or have.

How would this LNBF mount to a prime focus dish? Does it require a mount like the dual circular in one of the photos above?

 

[Titanium]

Here are two examples of manufactured 40mm clamps for prime focus dishes.

I have also created spacers out of PVC pipe to enlarge the LNBF 40mm throat to fit a 62 - 65mm prime focus scalar opening. If the C-band scalar affected the KU band operation, I have reversed the scalar so the rings faced outwards away from the reflector.

 

[polgyver]

I did some primitive drawing and now see that I over-estimated the area of dish "seen" by typical Ku offset LNBF (it would be less than 1 m).
But, hey, it is still better than 90 cm dishes most members use...
I suggested SL2PLL, as you need double output. But, just for trial of "Q", you could use - temporarily - any LNBF.
Probably some axial adjustment would be needed.

 

[Titanium]

Polgyver, for an apple to apple comparison, estimate for reduced surface accuracy. Most pedal or mesh reflectors have reduced surface efficiency, so the performance of the illuminated area will be considerably lower than a quality offset design 90cm.

 

[fred555]

Polgyver, for an apple to apple comparison, estimate for reduced surface accuracy. Most pedal or mesh reflectors have reduced surface efficiency, so the performance of the illuminated area will be considerably lower than a quality offset design 90cm.

So a 6 foot solid prime focus petal dish will perform worse than a 90cm offset on Ku?

 

[Titanium]

So a 6 foot solid prime focus petal dish will perform worse than a 90cm offset on Ku due to less illuminated area??

When a KU LNBF designed for illuminating a FD .5 - .6 offset dish is mounted on a prime focus dish (FD .32 - .44 typical), the LNBF is only illuminating a portion of the reflector. If the LNBF is only receiving the signals reflected from an area that is equivalent to a 1M dish, then the less efficient surface combined with the shadow from the feedhorn (or LNBF) will produce much less signal gain than an offset 90cm. A petal, prime focus dish will have reduced accuracy, efficiency and performance than a similar surface area offset design.

Mount a feedhorn with KU LNB (or a KU LNBF) that is designed to illuminate a FD .32 - .44 reflector on a petal prime focus dish with corresponding FD and the entire surface area will be illuminated. The additional surface area will provide signal gains far in excess of that which is lost by reduced surface accuracy and the feedhorn shadow.

 

[fred555]

When a KU LNBF designed for illuminating a FD .5 - .6 offset dish is mounted on a prime focus dish (FD .32 - .44 typical), the LNBF is only illuminating a portion of the reflector. If the LNBF is only receiving the signals reflected from an area that is equivalent to a 1M dish, then the less efficient surface combined with the shadow from the feedhorn (or LNBF) will produce much less signal gain than an offset 90cm. A petal, prime focus dish will have reduced accuracy, efficiency and performance than a similar surface area offset design.

Mount a feedhorn with KU LNB (or a KU LNBF) that is designed to illuminate a FD .32 - .44 reflector on a petal prime focus dish with corresponding FD and the entire surface area will be illuminated. The additional surface area will provide signal gains far in excess of that which is lost by reduced surface accuracy and the feedhorn shadow.

I think I'm reading this as an sl2pll ( or any other Ku lnbf designed for an offset dish) wont work but an invacom on a c120 flange or this will work ?

EDIT: The Viking Satcom above has a published FD range of 0.335-?0.425.

 

[Titanium]

An SL2PLL is designed for an offset dish with FD .5 - .6. Like any other KU LNBF designed for this higher FD, only a portion of the 6' dish will be illuminated.They work, but only will receive a portion of the reflected signal.

The GEOSATpro SL1P, Invacom ADF-120 with LNB or the unit in your photo is designed for prime focus dishes and should illuminate the reflector properly. Of the three, I personally would use the Invacom ADF-120 and the Inverto Black LNB. The Invacom ADF-120's FD is adjustable where the SL1P and the one in your photo are fixed.

 

[fred555]

An SL2PLL is designed for an offset dish with FD .5 - .6. Like any other KU LNBF designed for this higher FD, only a portion of the 6' dish will be illuminated.They work, but only will receive a portion of the reflected signal.

The GEOSATpro SL1P, Invacom ADF-120 with LNB or the unit in your photo is designed for prime focus dishes and should illuminate the reflector properly. Of the three, I personally would use the Invacom ADF-120 and the Inverto Black LNB. The Invacom ADF-120's FD is adjustable where the SL1P and the one in your photo are fixed.

Thanks for the clarification, Its been a long week and I can barely comprehend anything tonight.

 

[iBoston]

Wouldn't something like this work? It claims it is for Prime Focus Dishes??

http://www.aliexpress.com/item/High...ocus-LNB-For-signal-weak-area/2021698155.html

 

[fred555]

Wouldn't something like this work? It claims it is for Prime Focus Dishes??

http://www.aliexpress.com/item/High...ocus-LNB-For-signal-weak-area/2021698155.html

My whole deal is whatever I do I need dual output. FTA feeds all TVs in the house with multiple stationary dishes through powered multiswitch bank.

 

[Cham]

Good option might be to modify one of Brian's dual LNBF units to attach to the C120 flange type scalers. They are not terribly expensive, one of the members here likely has a feedhorn kicking around that they might part with (sell/give away)... This would certainly be the most simple (electrically) solution.

I am thinking a dual LNB ortho feedhorn and a powered SW44(?) would be the best (of course not the cheapest) option for the absolutely best signals.
Found a feedhorn and OMT adapter:

http://www.avcomm.com.au/ku-band-dual-polarity-feedhorn-detail

Maybe finding a deal on a C/Ku ortho used with LNBs might be another way to go rather than a new Ku feedhorn with new LNBs etc. A 6' dish would pick up some C-band signals... maybe not S2 stuff.. depending on what satellite you are pointing at.