One Meter Primestar Mini-Bud Experiment

[linuxman]

I didn't want to steal Satcom1's thread, so I am starting my own.

I was so inspired by his post, and just so happen to have a real life possibility that I am going to give this a shot and see what happens. I am hoping to get EWTN on Galaxy 17 C-Band along with whatever else I can get across the arc on C-Band plus all the Ku channels.

I am going to use my 1 Meter Primestar round dish and my SatAV CK-1 LNBF.

My son and I brought the 1M down from the roof yesterday morning, and I took down my motorized 84e and put that dish on the mount for Hispasat where the 1M used to be.

I wanted that motorized mount, because I put a little "extra" into it when I put it together such as an adjustable mast for setting the plumb, along with a real schedule 40 pipe.

I will be using my SG2100 for moving the dish, and have started putting together the scaler ring to hold the CK-1.

I shot some pictures while I am going through the project along with some numbers.

I will tune in the dish with the OEM Primestar LNBf first to make sure it is tracking the arc with USALS before going to the CK-1.

The focal distance to the OEM feed-horn is 28 inches. That is where I will try and set the CK-1 when I start that phase.

Here are some pics:





I didn't want to make new arms, and my opinion is that the LNBF should be held in place by it's scaler ring, so I started cutting and fitting. As it sits currently, the mouth of the feed-horn will be at 28 inches when recessed flush with the inside circle of the scaler. That would give a F/D of roughly .46 if that means anything on the CK-1.

I am also going to follow SatAV's choice in using a power passing on both sides splitter to allow the signal to go around the SG2100 instead of through it.

See SG2100 Insertion Loss thread.

Hopefully I can get the dish on the motor and start tuning later today or in the morning.

 

[satcom1]

Linuxman,

Stogie had those same plastic boxes on his masts. Great place to mount switches, where do you get them? Or what are they from?

 

[linuxman]

Linuxman,

Stogie had those same plastic boxes on his masts. Great place to mount switches, where do you get them? Or what are they from?

I get mine locally from Skywalker. They are just cable tv type boxes. Very cheap, and has places for the coax to come in and go out.

I have one on every dish I have ever put up. I use a RG-6 4-port grounding blocks inside so I can unscrew the coax when I want to hook up at the dish.

I also use an 8 wire terminal block inside there on the BUDs so I can hook up the GBox and servo control wires at the dish with alligator clips. Makes it easy to work on them.

I was just sitting on the roof yesterday taking a break and counting up the money I had tied up in just switches, wires, concrete blocks, non-pen mounts, and other things besides the dishes, actuators, and receivers. I almost passed out and fell off thinking about it. :yikes:

 

[voomvoom]

I like the way you've have modified that feedhorn. I hope it's in the right place? It looks good, how about a picture of it alone, and off of the P*?

 

[gabshere]

i was wondering if you calculated the F/D & length ? .. i've seen some located beyond the original arms and some raised higher ... i think caddatas was like that
looks like a good project though

 

[linuxman]

Hey Al and George,

Here's the picture of the scaler off the Primestar.



I didn't calculate anything. I measured. The focal distance should not change whatever feed-horn you are using.

If it is 28 inches to the mouth of the OEM feed-horn, that distance should be used for any other feed-horns you try. I am sure that Channel Master tested these dishes and determined where the best distance for gaining maximum signal should be.

Granted, that may not be the best place for C-Band, but on this dish, C-Band will only be a bonus side gift. If I calculated for C-Band and set it there, I might lose all Ku and would have gained nothing.

That's part of the reason I am using the scaler is so that I can slide in and out a small amount to get the best signal for both, but this is the proper place to begin unless I am horribly wrong.

I might need to move the scaler further out, and I am prepared to do that.

 

[gabshere]

i think in his (caddata's) pictures his looked more like positioning for a prime focus dish after adjusting the feedhorn. i don't know if he was after ku.

 

[gremlin411]

Man I love this site!!!!

linuxman you and satcom1 have really got it going on with the testing you all are doing. And the pic's are great. I have been trying to figure out how to get by BSC-621 on my 1.2 or 1.8 prodelin offset dish so long my head hurts I just can not think outside the box like you do. took me two months to find 123. LOL !!!!!!!!

Please keep the pic's comming.

 

[linuxman]

Man I love this site!!!!

linuxman you and satcom1 have really got it going on with the testing you all are doing. And the pic's are great. I have been trying to figure out how to get by BSC-621 on my 1.2 or 1.8 prodelin offset dish so long my head hurts I just can not think outside the box like you do. took me two months to find 123. LOL !!!!!!!!

Please keep the pic's comming.

Thanks Gremlin!

Ah, every now and then I get a hair up my backside and have to do a little experimenting. I just hope I can get a little C-Band signal.

Hey George,

I need to go back through Caddata's thread and look at his pictures, but I think you may be right if memory serves. I think he was trying for best C-Band. I'll see if I can find his thread.

 

[gabshere]

i was thinking the ku might be offset and the c band slightly above it maybe further out
would maybe do better with something like this. but this is me guessing go ahead with your test and we will see how it does

yuri

 

[linuxman]

I found Caddata's thread here.

I have also taken the liberty to snag his bmp drawing and have saved it as a jpeg file.



Here are a couple of quotes from Caddata in that thread.

I know that some of the adaptions have moved the C/Ku feed further away from the dish. If my layout and dimensions are correct, it appears that those adaptions have placed the C/Ku feed on the far side of the focal point convergance. The signal actually makes an "X' at the focal point and widens as it passes further from the dish. Just as light does as it passes thru a lense.

Here is the second one.

I've seen this idea of the focal point of the Ku being different from the C, and I can't bring myself to believe it because microwave behave exactly as lightwaves.

A mirror doesn't know what color of light it reflects, just as the dish doesn't know the frequency of the waves (light, sound, or electromagnetic) it's reflecting. Everything that hits the surface of a dish gets reflected to the same focal point. Lightwaves, soundwaves, and electromagnetic microwaves are all at the same focal point. Have you ever been working near the focal point of a dish and heard the "sounds of nature" (birds, wind, leaves rustling)? My first encounter fascinated me. The dish had been rotated all the way to the West and was about 6 feet off the ground. I stopped working and turned my good ear to the focal point and was suprised at the things I could hear.

Once the feedhorn is located at the proper focal point, the focused signal (containing both C and Ku waves) enter the C band resonate cavity. The focused signal is like an onion with higher frequencies at the center in a ball, layered outside are lower frequencies in progessively larger balls all with the same centerpoint. C band waves find the C band probe inside the first resonate cavity. As the rest of the collected signal passes into the Ku band resonate cavity Ku microwaves find the Ku probe and resonate to it.

Harold

So from the depths of my sub-conscious mind came a bit of Harold's wisdom into what I have written today.

The C-Band and Ku band have the same focal distance.

 

[voomvoom]

The C-Band and Ku band have the same focal distance.

Yes, but the C/Ku probes are generally in different spots/depths inside the tunnel. And I think that is what makes them different? And also why, on the BSC-621 (standard) or the C/K1, I could not get both C-Band and Ku-Band at the same time/together?

 

[linuxman]

Yes, but the C/Ku probes are generally in different spots/depths inside the tunnel. And I think that is what makes them different? And also why, on the BSC-621 (standard) or the C/K1, I could not get both C-Band and Ku-Band at the same time/together?

That's a mystery to me too Al.

I had both pretty darn good on the Perfed Birdview at one time using the CK-1, but have never been able to repeat it. I changed some things around on that dish, moved it to another mount and then moved it back, and just now have it back to the SQ I once enjoyed only with the Co-Rotor and am now using the Bullseye II on it.

I could probably put the CK-1 back on there now and it would be fine again.

That's why I am going to tune this 1M primestar with the OEM LNBf to start with and get the dish fine-tuned. Then put the Ck-1 on and see what happens.

Theoretically once the signal gets inside the mouth of the feed-horn, it can't go anywhere else, so it should go on down the throat and find it's probes. Sadly on the newer models it doesn't most of the time.

 

[voomvoom]

It's probably more forgiving on the BUD, but I was experimenting on a 1.2m dish and tried both the BSC621 and the C/K1, I was able to get some (actually few) C-Band channels with both, I was able to get Ku-Band signals as good as most ku lnbf's with both. I just couldn't get the C-Band and Ku-Band to work together at the same time...??? I went on to other things, but will get back to playing around with them some day...... maybe..??
I stopped partly to try and find a Conical Scaler Ring, and was finally able to get 2 from a member here. I just haven't gotten back to it. No excuse's.......

 

[linuxman]

It's probably more forgiving on the BUD, but I was experimenting on a 1.2m dish and tried both the BSC621 and the C/K1, I was able to get some (actually few) C-Band channels with both, I was able to get Ku-Band signals as good as most ku lnbf's with both. I just couldn't get the C-Band and Ku-Band to work together at the same time...??? I went on to other things, but will get back to playing around with them some day...... maybe..??
I stopped partly to try and find a Conical Scaler Ring, and was finally able to get 2 from a member here. I just haven't gotten back to it. No excuse's.......

Well, hopefully this will work and that will re-inspire you.

 

[satcom1]

caddata post

Because of the wavelength difference between C and KU there should be a significant change in focal point and phase of received RF.

If you consider:

1- The BSC621 is designed for a large dish which has many wavelengths between the dish and the feedhorn, phase error may be cancelled more then on a close coupled small dish.

2- The dual LNBF design uses the C band section as a waveguide to couple KU energy to the KU feedhorn Scalar ring deep inside. There is likely impedance matching and phase error cancellation going on there too. All this would be mis-matched and detuned on a short coupled dish.

3- DREAMFOX1 has what I consider to be very good performance on a 1 Meter Offset Dish. If he had placed the C Band LNBF above the KU LNBF then alot of energy would be cut off to the dish. By placing it to one side and moving the dish to re-focus it, a better signal is received by both LNBF's.

Linuxman-

I hope you are going to use a C band only LNBF for your first experiment. The Primestar is such a good performing dish, I expect you to get better results then DREAMFOX1.

 

[linuxman]

I hope you are going to use a C band only LNBF for your first experiment. The Primestar is such a good performing dish, I expect you to get better results then DREAMFOX1.

I will be tuning the dish first with the Primestar LNBF and get it fine-tuned for Ku performance.

I will then switch it out with the CK-1 C and Ku LNBf that I bought from SatelliteAV about a year ago.

As far as the focal point of the dish goes, there is only one focal point, otherwise it wouldn't be focal. It doesn't matter whether it is C-Band signals, Ku Band signals, light beams, etc. they will all focus at one point and one point only.

The dish is just a reflector and the reflection of whatever will all be focused at one point, that is where all best signal will be.

 

[satcom1]

Yep, and you'll get same results as all of us others. Two seperate focal points for C and KU to far apart to make a comromise with.

 

[linuxman]

Yep, and you'll get same results as all of us others. Two seperate focal points for C and KU to far apart to make a comromise with.

Unfortunately that has been the pattern for both the CK-1 and the BSC-621 on both big and little dish.

But as I was telling Al earlier, at one time I had both C and Ku pretty darn good on the Birdview Perforated dish. The only reason is because of the outstanding surface reflectivity of the Birdview dishes.

I would expect no less a surface reflectivity from a Channel Master/Primestar dish, so we'll just have to wait until I get done to see.

 

[Anole]

how low will you go?

. . . yea, and knowing Linuxman . . .
If he can't make it with the Ck-1, he'll graft on an Orthomode and put you all to shame!
At least that'll look like it's just got one focus point!

Or, if Sadoun ever gets those Vboxes with corotor control, maybe . . .

I stopped partly to try and find a Conical Scaler Ring, and was finally able to get 2 from a member here.
I just haven't gotten back to it.

Why not loan one to Linuxman? He'll play with it like nobody I know.
And if it'll improve performance, he'll demonstrate it.
Save you a lot of experimenting.

I don't personally have a lot of expectations of this project, but the conical scaler might make it happen.

I'm keeping on the lookout for a conical for use on a 1.8m Prodelin , 'cause I know it'll require one.