123w & 125w Super Dish Network 24x34" elliptical dish

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avg1joe

SatelliteGuys Pro
Original poster
Oct 27, 2006
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Southern Maine
A few months ago I got a free direcpc dish and was pretty impressed by its reception.

I put an ad on free-cycle for midsized satellite dishes and was given two identical Super Dish Network dishes. After researching what exactly I had, I read the 125w, two degree threads and the 123w/119w dish mod thread. Someone suggested these two ideas should meet so I thought I'd give it a try.

I removed the cover from one and noticed that there were light gray modules labeled FSS and DBS. I started to wonder if there was any wisdom in just replacing the DBS module with a FSS module. I doubted it would be that simple but thought it was worth a shot. So I removed the FSS module from this donor dish.

When I removed the cover from the second lnbf assembly I almost soiled my pants. Nearly the entire interior was filled with a hornets nest and dead (luckily) hornets poured out onto the floor.

I replaced the DBS module on this dish with the FSS module from the other dish.

For a baseline, I checked out a few of the transponders on 123w and 125w using the signal meter built into my visionsat, and my winegard 76 setup. I found quality to be in the 80's. It was partly cloudy and very windy.

Using the mount that came with one of the dishes I screwed the super dish mount to some wood for a temporary setup. I had a bugger of a time aiming this heavy dish with my light, wooden, ghetto mount but once I did I was able to hit 125w using the original FSS module and oval feedhorn intended for 121w. I found my quality to be in the 80's. With a little adjustment and using the same feedhorn I was able to hit 123w with quality in the 80's as well. I was very impressed by this performance on a free oval dish.

Granted this was hooking the super dish directly to the receiver with less than 6ft of cable. The winegard has a motor in the mix, 100ft of cable and a ground block.

I aimed the oval feedhorn at 125w again and hooked the cable from the round 119w feedhorn to the the receiver which should now be aimed at 123w. I was immediately encouraged by retrojams popping up on the tv. I was able to get quality of about 67% without compromizing the quality in the 80s on 125w. This setup was too floppy to waste time with much more fine tuning.

I did a blind scan on 123w to see what would pop up. The wind was visibly shaking the dish while scanning. The scan found what I believe was KTWO, retrojams and possibly 3CTV (cea or cee?). Curiously it scanned in about four copies of each channel. For instance KTWO was on two different TPs at about 12104 and two different TPs at about 12495.

None of the lower transponders scanned in. I'm guessing this is the fault of the feedhorn although it is possible that these are weaker transponders.

The next time I have free time I will get out the hacksaw and setup both modules with the oval feedhorns.

In the pictures you can see my ghetto dish mount and where I replaced the FSS module. I am holding the DBS module above the FSS module that I replaced.






 

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SuperDish 121°, on 123+125:

I had read that the 119° side of the feed horn duo (the little round one) wouldn't work for FSS.
Something about the feed having some steps inside the throat, which converted the signal from circular so the LNB could read it.
Glad you went ahead and gave it a try. Impressive that you got reception.

Looking forward to seeing what you come up with, after hacksawing off a second oval 121° feedhorn, and running with two of those.
They should match the oval dish better, and get you more signal.
 
Anole is correct about the 119 feed having a couple of flats at 45 degrees just after the mouth. These do convert the two circular polarizations into two linear polarizations. Technically one can convert this type of feed to pure linear by rotating it 45 degrees either way and offsetting the LNB also by 45 degrees at its mount to the feed. Unfortunately doing this to a SuperDish 119/121 feed means you have to saw it apart anyway, and using two 121s together should mechanically work better than one 121 and a rotated 119.

I may be wrong about this, but it's not obvious to me why linear polarizations into a non-rotated 119 feed wouldn't still work. It's possible the flats would increase the cross-polarization, though.
 
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what goes around . . .

I brought this up about two years ago, but never followed through.
The parts slipped through my hands, at the time.
Glad to see someone going forward! - :up

What I did pick up in the intervening years, is a similar LNB with a larger oval feedhorn.
Had plans to put two of 'em at the focus of a DirecPC dish , for 123°/125° experiments.
Now, I have all the parts, but there are other things to do. ;)
 
Avg1joe;

Nice solution! I was getting adjacent signal interference on my SD's for 123/125, but they are modded different. Maybe the metal in between two sawed off 121 sections will do the trick!

They're not bad as fixed dishes, especially for the price! :up
 

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Direcway 123/125

avg1joe,
I have a direcway dish that I have been playing with for 123/125, so I though I would share what I have tried. The direcway dish I have had an oval feedhorn similar to the one on the LNB that Anole mentions. The LNB from the direcway dish was very heavy, so I managed to replace it with one of the bandstacked FSS lnbs from a superdish 105 while using the oval feed horn that was originally on the direcway dish. This LNB is used for 123w.

For 125w, I took the FSS LNB and feedhorn from a superdish 121 like you are using. I had to cut it away from the DBS LNB and feedhorn in order to make it fit on my direcway dish. The direcway dish had a place for a DBS LNB that they call a lip stick LNB since it was very small and didn't have much of any feed horn. Luckily, the FSS lnb from the superdish 121 fit in this spot very well and the angle of the feedhorn allowed the LNB to sit out of the way. Since I had to cut the superdish feedhorn apart, the plastic cover no longer fits. For now, I have just covered it with electrical tape to keep the moisture out.

I also taped an old DBS LNB to the side to get the NASA channel at 119w.

I have been using this set up with a skystar2 pci card and mythtv. When it actually decides to switch the diseqc switch, it seems to get usable reception. It doesn't really give me any useful signal or quality measurements to share.
 

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I may be wrong about this, but it's not obvious to me why linear polarizations into a non-rotated 119 feed wouldn't still work. It's possible the flats would increase the cross-polarization, though.

Senior moment corrected for the archives: a feed like this is reciprocal. With the flats at 45 degrees with respect to the LNB probes, it will properly convert L&R to H&V, but also H&V to L&R. If the flats are parallel and perpendicular to the probes, The LNB will pick up H&V, but L&R will be combined on both outputs.
 
Thought I'd share a picture of one step farther along to show what pendragon was talking about. I unscrewed the front from the back of the metal feedhorn and then sawed the part (I'll call this the front) with the oval and round openings apart.

In the picture I'm holding the back upside down so that the the tubes they mate with are on above and below each other. You can clearly see the protrusions on the inside of the dbs tube.

My next step will be to saw apart the other lnb and reassemble it with two oval feed horns. My plan is to only swap half of the front and to leave the back intact rather than sawing it in half all the way back.

I'm somewhat concerned that the tubes in the back are different. The previously dbs one is round (but smooth, the protrusions do not go all the way into the back portion) but the tube fss is square. Time will tell if this squareness serves a purpose.
 

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Eureka!

Functionally I'm done with this project and I'll declare it a success!

I sawed apart the other lnbf tonight and reassembled it using the donor pieces. It was another nice day today and a bit windy again. I was still using my ghetto shaky setup to test out the modified FSS+FSS Dish Network dish. I locked onto 123w first and retrojams with quality solidly in the 80s. Without moving the dish I switched the cable to the 125w lnbf and imediately hit a pbs TP with quality in the 80s. I didn't spend too much time tweaking but found usable signal on all channels on both birds without moving the dish.

The old white plastic lnbf covers won't fit any more. I was going to cut them and modify them but they cracked when I started cutting them.

What materials are invisible to satellite signal? Plastic, rubber, .....? Any suggestions on how to cover the lnbs?

I'm wondering what would happen if I put this lnbf on my winegard.
 

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Joe;

A Very cool and clever solution, may I borrow the idea for one of my SD's?

As for the correct plastic for a cover, you have the setup for another great experiment!

Soda bottles, visqueen, landscape plastic, PVC, milk jug, teflon, glass, etc.

It would be a genuine apples to apples comparison. It would possibly solve the problem reported of some C band lnb caps wrecking signal Q.
 
Winegard 76cm? Too short a focal length, I'd wager.
Try it and tell us, or do the calculations (I'm too lazy and don't think it'd work)
What is your minimal LNB center-to-center spacing you can set?

In addition to all the interesting bottles 'n stuff Cadsulfide mentioned, what about some Tide Liquid washing detergent lids, or some Saran wrap?
 
Cadsulfide, this forum is all about poaching and improving on the other guys ideas. Go for it. I stole the idea from threads by Sidha and Anole among others.

I keep thinking about the properties of the cover I'd like to use. It should be stretchy and waterproof but the material shouldn't be too thick.... My mind keeps going back to using a condom but my neighbors already think I'm nuts and that would not improve their impression of me.

I live in a townhouse style building. I setup my temporary setup on my front sidewalk last night to try this out. I was waiting for someone to come pickup a nordic track skier I was selling so I set that outside on the sidewalk next to me as well and actually used that to weigh down the board the dish was attached to. This stabilized the dish some in the wind. I have a new neighbor who I don't know well. He gave me an amused look as he walked by. I was very tempted to yell out, "I need more power to contact the mother ship. Jump on the Nordic track and ski, man, ski!" In hindsight I should have gotten a pic of that.
 
I used to travel my Dish 300 and would cover it with a large garbage bag (black). One time I decided to leave the bag on the dish (covers the lnb also) as I set it up and did not have any noticeable effect. I decided to start leaving it on whenever I traveled or was home.
In another experiment I found the grocery store bags (just on the lnb) will work also but they degrade too quickly in the sunlight.
 
The problem is that many disposable plastic products are designed to deteriorate in UV light due to environmental concerns. Plastic grocery bags are an example of this. Garbage bags are probably designed this way as well. Something like Visqueen might work better in UV light.
 
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