I'm having a nightmare....please help!

[frizzle1002000]

I'm currently based in the Uk and I'm trying to set up a dish on a polar mount for a motorised system using a superjack actuator and I'm finding great difficulty in understanding the various angles with which to establish correct elevation to point the dish on the arc to begin with.

My latitude according to Dishpointer is 53.774 degrees.
The declination angle is therefore 7.6 degrees.
The Reflector offset angle is 22.3 degrees.

I've got the dish pointing south and at it's zenith but here's the rub.
According to the information sheets that came with the mount I add the reflector offset angle to the declination angle and this becomes a total of 29.9 degrees.

There is an 'hour angle' pivot plate which should be set at an angle 29.9 degrees lesser than the reflector support tube which is parallel with the reflector face (I created this angle by unscrewing a nut on the declination adjustment rod and on doing so cross-threaded it, so I sure hope I don't have to touch that thing again!)

The info sheets then mention placing the inclinometer back on the hour angle pivot plate and setting it to the latitude angle which I assume is 53.774 degrees.

If I do this the elevation angle of the relector measured at the bottom rib is roughly 46 degrees which I presume is not correct.

If anyone could get me back on track I sure would appreciate it.

 

[Lak7]

This may help...
Footprints by Dish Size - Adjusting the Polar Mount for Prime Focus Antenna - C/Ku-Band Satellite Systems - Tuning, Tracking, Azimuth, Elevation, Declination Angles, F/D Ratio, Focal Distance, Inclinometer, LNB/Feedhorn Assembly, Actuator Assembly, C

 

[Lone Cloud]

If that photo is your actual setup, it looks like you have way more than a seven degree difference between your dish face and the axis of your polar mount. It looks more like 20 +.

If it were me doing it, I'd first set my mount on due south - by that I mean where the top of the dish is at its highest point

. Then I'd go with the declination angle and get it right. That bar on the back of the dish looks like one place to get a reading on your inclinometer. It's hard to see where you would take your "polar axis mount" angle from. Just remember that the base of the inclinometer has to be parallel to the bolt or axle that goes through the mount That's the polar axis. To me it looks like you are going to have to mess with the bolt again. I know this sounds basic, but, when you turn your inclinometer around to get readings, you don't just get the angle numbers off the tool.

Look at it this way - imagine your dish face is exactly parallel to your polar axis angle - your bolt or axle the whole thing is going to swivel on. You have to adjust the dish out at the top seven degrees (only) Sort of like a very skinny "V"

Then I'd set my receiver for my due south satellite. You could bring a little tv and your receiver up to your dish, but I personally like to use wireless headphones and set my receiver on "beep for scanning" (Viewsat Ultra) . With the bolts loosened so you can spin the whole rig on your mast, and with the dish angle bolts ( not the declination, that's already tightened) loosened too, you go to the next step.

Set your receiver settings for the lnb you're using and a transponder and channel you know is hot. Then you dance with your dish until you find the channel. That means you lift the dish up and down and you twirl it back and forth on the mast until you find your signal . For me, with the wireless headphones on, I do that and when I hear the beeps going fast, I tighten the dish. Small adjustments after that.

If you are using a little tv and your receiver on your roof, get the "quality (Q)" signal as high as possible. Tighten. Later on, after you find the farthest east and west satellites you can get, that will help you fine tune the adjustments.

Hope it helps. Works for me. Good Luck

 

[Anole]

Prodelin 6 foot offset dish

If that photo is your actual setup, it looks like you have way more than a seven degree difference between your dish face and the axis of your polar mount. It looks more like 20 +.

Yes, I believe he has this dish, but on a motorized mount.
That leaves it leaning forward a lot.
Looks funny, I know.

 

[Lone Cloud]

Since a picture helps, I'm attaching one that shows the approximate angle the bar should be set on

 

[kiwisat]

Nice work LC, I have just tonight joined this forum, and I am very impressed by your advice given. It is not easy to explain the concept but you have covered it very well.

 

[Lone Cloud]

Thanks for the words kiwisat (NZ?) C-band experience I think gives you a little better understanding of the concepts than does Ku.

The arc, the Clarke Belt, is an orbit directly over the equator. That means that, on the equator there is no declination offset angle. When we travel toward either pole, if we could see the CB, it would appear more and more curved.

C-band helped me to see that with my mind's eye. Ku is fun, but with C I'm learning more.

Thanks

Thanks

 

[Anole]

The OP has an offset fed Prodelin dish as shown in this picture.
His offset angle is 22.3° , as listed in his first page-scan.
So, the apparent 20° error, is actually normal.

We don't see such lashups here in North America, but in Europe, big offset dishes on these sort of mounts are more common.

I've found the Geo-Orbit site very helpful in understanding the geometry of dish alignment.
Offset dishes are quiet similar to the prime-focus dishes shown.

 

[Lone Cloud]

You could be right, Anole. An offset dish would change the angle between the polar axis and the dish.

Such a large offset dish is a bit new for me.

Remember Gilda Radner?

"What's all this fuss about violins on television. I love violins. They make beautiful music"

" No. It VIOLENCE on television, not violins"

"Oh. That's different. Never Mind"