? offset angle Primestar 1.2m

[Magic Static]

I've been missing a few game feeds on Ku so I decided to motorize an old Primestar 1.2m dish. I plan on modding a prime focus mount for the purpose. So I need to know the offset angle of this dish.

 

[primestar31]

I believe it's 22.6 degrees. That's a Channel Master dish.

I found my old manual, offset is 22.6 for sure. Use strong angle-iron to create your cross braces for the polar mount, as you have to tip the top forward, and this dish gets pretty unwieldy when doing so.

 

[phlatwound]

Can't wait to see what you come up with on an adaptation to a prime focus polar mount, I've been wanting to try that for quite a while.

I've put a 1.2m and a 1.8m offset on an AJAK but never on a polar mount.

Good luck!

I never see any of the 1.2m Primestar dishes around here.

 

[primestar31]

I've actually got one of the rare ORIGINAL factory Channel Master 1.2m offset dish polar mounts in my shed, with the offset built into it... hehehe

I think I'll have my wife bury me with it, when that time comes... LOL

 

[waylew]

I've been missing a few game feeds on Ku so I decided to motorize an old Primestar 1.2m dish. I plan on modding a prime focus mount for the purpose. So I need to know the offset angle of this dish.

Here's my Pstar 1.2;

 

[RimaNTSS]

MS congratulations on your idea! Yes, the dish has 22.6* offset angle, as all CM dishes have (0.35m, 0.9m, 1m, 1.2m, 1.8m, 2.4m). Glass dish, even used for a long time is much better than any metal one, IMHO. Just some time it needs cleaning and that is all, it looks as new again. It looks nice but it also keeps it's shape much better. Therefore I always advice to anybody to buy used glass dish instead of brand new, made of tin one. I am pretty sure you will be able to fit your dish on polar-mount you have and it will go almost H-H.

 

[Magic Static]

I am pretty sure you will be able to fit your dish on polar-mount you have and it will go almost H-H.

I wish I had satellites H~H here. I'm at 114.0°W so I have sats for only 25° to the west and then I see the big void over the Pacific and finally catch 177W near the West horizon.
So basically I can see from 55W to 139W

 

[Magic Static]

I've been gathering tools and material for the project. A visit to harbor freight and I'm about ready to dive in. But the nice weather has abandoned us for the season I fear. So I have taken apart the mount and photographed the parts so I can study them and decide how best to proceed. Some cleaning and rust removal required on this one.


While I was out to the sat dish junk yard picking out a dish I visited the old BirdView perforated dish laying on the ground. I wanted to measure it so I flipped it over. The weeds had grown through the holes and made it a little tough to get. But finally. And found another BV solid dish under it The perf is 116", to bad it's so bent up.

 

[phlatwound]

It's been a while since I thought about how I would tackle a caper of the sort that you are embarking upon now.

Seems like I had considered not even using the mounting "ring", and just starting with the piece that mounts to the ground pipe and the big square tube and going from there possibly?

And that is a damn shame on the BV perf, that is the first documented 9'-6 BV perf reflector I have ever seen, there's a guy in NW Nebraska that sent me a pic of a 9'-6 solid BV reflector a couple years ago.

So they are out there, but few and far between methinks.

 

[phlatwound]

Here's my Pstar 1.2;
View attachment 128455 View attachment 128456

waylew, I can't really tell from looking at your picture but have you allowed for the offset of your dish (increased the declination by 20-some degrees over what a prime-focus dish would need)?

 

[Magic Static]

Seems like I had considered not even using the mounting "ring", and just starting with the piece that mounts to the ground pipe and the big square tube and going from there possibly?

I also considered that. The ring is essentially useless, just added weight. But it is a solid structure and easily adapted as is. I am going to cut the mounting ears for the C-Band dish off the ring and then check the fit to the dish. I think I can position it so that the dish will nest in the ring nicely when bolted down giving it added support. I have an idea for some rubber bumpers on the back of the dish where it contacts the ring. It should actually look pretty good. It's a small 23" ring. There is already a declination adjustment mechanism built into the bottom axis arm so that all I really need to do is replace the upper arm with a longer piece to add the offset angle. There is still a question off actuator mounting but I'm sure I can work that out.

 

[waylew]

waylew, I can't really tell from looking at your picture but have you allowed for the offset of your dish (increased the declination by 20-some degrees over what a prime-focus dish would need)?

Been so long since I set it up that I don't remember exactly what I did.But I think I modded the declination adjustment for the extra offset.Works from 72 to around 103 or so(roof gets in the way). Originally put it up just to get the DMX channels for the 4DTV when they were ku on the original X4 (99w),I just used the elevation adjuster to tune it in.
Two weeks after I had it set up and working they announced that they were leaving the ku sat and moving everything to the c band sat .So after that I made it a movable dish thru a lot of trial and error,but that was years ago.

 

[Magic Static]

Angle of the Dangle:
I cut the dish Mounting ears off the ring. I disassembled the mount so all I have is the axis tube and the ring. First I want to measure the built-in declination adjustment for this mount. With the dish ring at 0° I can measure my angles from the axis tube. I determined the declination of this mount to be about 2° ~ 8°.

Next I set the declination adjustment to my location at 7°. Now I need to add the offset of this dish (22.6°) so I have a total angle of just under 30°. This is where I take a measurement to find out how much longer to make the top arm. I came up with 5" of extra length needed.


I also checked the fit of the ring to the dish. I found it will not fit as I first envisioned but close.

 

[Magic Static]

K.I.S.S.
I have a tendency to over do stuff. But in the end the simple solution is often the best.
The place I buy my metal from is great, CDA Metals. The one guy in there really goes the extra mile for the customers. He's about 6'8" Bald about 35 years old and 3/4" gold gauges in his ears. Reminds me of Bull on Night Court. He always cuts my metal for me for free and this time I needed a 30° bend in my arm extension and he had me measure it up and bring it back to get done, perfect I picked up a short 2" wide 3/16th" thick strap rem to attach the dish with. In total I spent less than $5 there on the mod to this mount. It was a decent weather day and I dug out the welder and assembled the mount. I put the mount on my test stand so I can plan out the actuator attaching points. Looks like just remounting the ear on the ring to compensate for the 30° angle.

 

[KE4EST]

Nice work Mr. Static!!

 

[Magic Static]

I believe I have the mount finished. I have assembled the dish on the mount and all looks good so far. I need to fix up an actuator yet. I want to increase the counts per degree for this Ku feed hunter

 

[primestar31]

I believe I have the mount finished. I have assembled the dish on the mount and all looks good so far. I need to fix up an actuator yet. I want to increase the counts per degree for this Ku feed hunter

View attachment 128594 View attachment 128595

Well, you can make a new wheel with 2 extra magnets, OR maybe just extend the polar mount front actuator bracket out further with additional angle-iron. Even with just an 18" actuator and an extended mount bracket arm, a 1.2m dish like this should have very good resolution.

 

[Magic Static]

I replaced the sensor in a VonWeis actuator with one of my making and doubled the counts. The original sensor was 40 counts per inch. On a 24" actuator that gives us 960 counts for a full stroke. I took it to 80 counts per inch , a 1920 count per full stroke. I used a larger magnet wheel with still only 8 magnets but all magnets polarized the same way. With the correct spacing of the magnets the reed switch closes twice with the passing of each magnet thereby doubling the count.

I need to find a pole to mount this on still. The actual installation may be delayed until spring. We already have had snow, the earliest snowfall in 34 years. But I will be doing some testing with the test stand and maybe watching a game tomorrow on it

 

[primestar31]

I replaced the sensor in a VonWeis actuator with one of my making and doubled the counts. The original sensor was 40 counts per inch. On a 24" actuator that gives us 960 counts for a full stroke. I took it to 80 counts per inch , a 1920 count per full stroke. I used a larger magnet wheel with still only 8 magnets but all magnets polarized the same way. With the correct spacing of the magnets the reed switch closes twice with the passing of each magnet thereby doubling the count.

I need to find a pole to mount this on still. The actual installation may be delayed until spring. We already have had snow, the earliest snowfall in 34 years. But I will be doing some testing with the test stand and maybe watching a game tomorrow on it

Spring is a LONG way away! Ground can't be frozen yet. Worst case you could always build a fire on top of the spot you want the dish, heat it up to thaw it, then dig the hole.

 

[Magic Static]

Spring is a LONG way away! Ground can't be frozen yet. Worst case you could always build a fire on top of the spot you want the dish, heat it up to thaw it, then dig the hole.

Spring is always a long way off in Montana As for building a fire...the planned location is next to the house. Hmmm that might not be a great idea.