Custom Project GeoSatPro SL1p mated to C-120 Feed horn

[Pixl]

I had a new Geo SL1p that I never used because I discovered my 6ft prime focus dish was warped and took it down.

So I got to thinking how it would perform on a offset dish. I pulled the nose cover off, and sawed off the throat and filed it even with the scalar rings. Using a feed horn from a Channel Master 1.2m dish with a C-120 flange as a guide, I marked, drilled, and tapped four holes in the scalar ring. (you could substitute nut and bolt if you don't have a way to tap threads) Then applied a little RTV silicone seal to keep the weather out, and bolted the C-120 flange flush against the scalar ring with the 18mm throats lined up. I decided to do a comparison of the GeoSatPro SL1p against a Invacom SNF-031 and a Prime Star "pop can" NJR-2112F lnb's, all mounted to identical Channel Master feeds.

First up was the existing Invacom mounted on my 1.2m Channel Master dish.
I cleaned out all the TP's on three sats and did a fresh scan.

Next was the custom GeoSatPro SL1p.

And then the original Prime Star lnb.

Sat TP Invacom Q GeoSat Q Prime star Q

72w 11968 H 1666 72 71 71
72w 12148 V 2573 71 71 71
72w 11844 V 29657 76 76 75
89w 11989 V 4999 71 71 71
89w 11959 V 19530 71 75 76
89w 12173 H 11139 60 44 53
125w 12184 V 29997 76 76 76
125w 12039 H 3725 71 71 71
125w 12167 H 4443 71 71 71
average 71.0 69.6 70.6


Conclusion:
If you throw out the one low level TP from 89w these lnb's test almost identical!
Since the results are in close agreement even though using different priced and age lnb's it might say that the identical feed horns that match the dish is the key reason.
Anytime I've tested after market lnb's with their own feeds the results varied much more.
Good reason to use the original feed for your dish if available.

The GeoSatPro SL1p is a high performing lnb, and Sat AV sells them for $10. A small modification and you can have it bolted up to your original feed!




Satellite AV, LLC - Satellite Broadcaster Support and Equipment Distribution

 

[turbosat]

Nice work there pixl, interesting results. Who said there's nothing new under the sun, haha.

 

[KE4EST]

Very Nice!!

 

[Anole]

That's pretty neat.
Wonder if you have a Dish Network FSS LNB laying around.
See picture below.
Would be interesting to see how the bandstacked LNB holds up to the others.
It does pretty well with the proper / matching horn, and the picture shows some custom ones made by Magic Static.

 

[Pixl]

That's pretty neat.
Wonder if you have a Dish Network FSS LNB laying around.
See picture below.
Would be interesting to see how the bandstacked LNB holds up to the others.
It does pretty well with the proper / matching horn, and the picture shows some custom ones made by Magic Static.

Yes I have one,
I'll try to get it up on the dish later today.

 

[SatelliteAV]

Thanks for sharing your experiment. Great idea and tooling!

 

[Pixl]

Wonder if you have a Dish Network FSS LNB laying around.
Would be interesting to see how the band stacked LNB holds up to the others.

Anole,

I added a couple more players to the contest this afternoon.
I found one of your FSS stacked dish lnb's as well as a single polarity commercial lnb.

Next up was the Dish FSS that came off of a Dish SuperDish.

Then I mounted the single polarity commercial lnb. Had to scan vert, then come out and rotate 90 deg for the horz TP's and re-scan.

Sat----TP------------Invacom Q GeoSat Q Prime star Q Dish FSS Q Single Pol. Q

72w 11968 H 1666-------72--------71----------71-----------71-----------71
72w 12148 V 2573-------71--------71----------71-----------71------------71
72w 11844 V 29657------76--------76----------75-----------76------------76
89w 11989 V 4999-------71--------71-----------71-----------71------------71
89w 11959 V 19530------71--------75----------76-----------76------------76
125w 12184 V 29997-----76--------76----------76-----------76------------76
125w 12039 H 3725-------71--------71----------71-----------71------------71
125w 12167 H 4443-------71--------71----------71-----------71------------71


So even the Dish lnb and the standard Ku lnb delivered readings in close agreement.

The Dish L.O. was off quite a bit, probably why it was taken out of service, and with the stacked math you have to do for horz, I would recommend these except for a fixed dish you don't scan much. The single polarity is fine for a sat you only need one side such as 125w, not much on horz.
So if you are looking for a C-120 bolt up lnb, with a small modification the GeoSatPro SL1p performs just as well and is much cheaper than an Invacom.

From my own experience trying to mount an aftermarket lnb on a Channel Master or Prime star dish is a cobble job because the focal point is so far in front of the mount clamp. If you don't have one of these dishes you should.
1.2m dishes are all over the place on top of banks, gas stations, investment firms, all for the asking. Many are out of service due to networking of these places. The original feed is very good, and if you are not using it, you should. Get a C-120 lnb, or make one yourself. Easy!

 

[Cadsulfide]

nice set of measurements!

 

[Pixl]

I can only guess that there some parameters missing from my tests.
Carrier to noise, and L.O. stability would be factors to take us to the next level.
At this point I conclude that the feed horn is the major factor in lnb performance, followed quickly by the electronics inside the lnb.

Mr. pendragon or others please weigh in on this.
thank you

Jim

 

[Anole]

Usually, when we compare different LNBFs, the numbers are all over the place.
Of course, each LNBF has its own scalar/feedhorn.
Here you are using different but identical feeds, right?

Some time back, Pendragon had a thread where he used a DishNet bandstacked FSS LNB.
In one test, he used the small DishNet 105° feedhorn.
In another, he crafted a more normal sized feedhorn from a DSS LNBF (as I recall).
The bigger one performed better.
Or maybe it matched the dish better...?

Looks like there is good room to explore LNBs and feedhorns again.
Oh, congrats and thanks for the initial discussion using the SL1P LNBF, too! - :up
I certainly won't be shy about mating non-standard pieces together in the future, thanks to the eye-opening ideas in this thread.


Pendragon compares Ku feedhorns with Dish 105° horn:
http://www.satelliteguys.us/free-ai...4-bandstacked-shootout-why-amps-good-bad.html

Tech#344 builds his own feedhorns for DishNet 105° LNBs:
http://www.satelliteguys.us/242947-question-about-multi-switches-2.html#post2461471

Magic Static makes feedhorns from old DirecTV Phase III LNBF:
http://www.satelliteguys.us/free-air-fta-discussion/253299-dish-dtv-=-fta-dish-fss.html

 

[m3repair]

Where did you get those waveguides from? I am on the hunt for one

That's pretty neat.
Wonder if you have a Dish Network FSS LNB laying around.
See picture below.
Would be interesting to see how the bandstacked LNB holds up to the others.
It does pretty well with the proper / matching horn, and the picture shows some custom ones made by Magic Static.

 

[Anole]

Where did you get those waveguides from? I am on the hunt for one

Often, old commercial dishes taken out of service, have the feed with 'em.
If not, sometimes they show up here on the forum, Craig's List, swap meets, Ham conventions, or in certain trash cans

See also, the three links at the bottom of my post #10 (above) for info on making 'em out of parts you might have.

 

[Pixl]

Here is one place, Channel Master Feedhorn, but I think there are some cheaper sources out there.
Anole is right, I got mine off dish's I've taken out of service.
Even some other FTAers have these laying around because they didn't realize their full potential and replaced with after market lnb's.

 

[Franky_D]

Very interesting thread and the results!!! Thank you for the great comparison!

Anole,
From my own experience trying to mount an aftermarket lnb on a Channel Master or Prime star dish is a cobble job because the focal point is so far in front of the mount clamp. If you don't have one of these dishes you should.

I was wondering if it would be possible to quaticise comparison between aftermarket LNBs used on the CM dish without and with the feed horn and compare for example:
1) Invacom SNF-031 + CM feed horn vs. 2) Invacom SNH-031.

How much difference (in % of the signal strenth/quality or dB) should one expect?

Thank you

 

[KE4EST]

Welcome to Satelliteguys Franky_D!!!!

 

[Franky_D]

Welcome to Satelliteguys Franky_D!!!!

Thank you ke4est!