C Band Dish Installation Update

[lost_mesa]

I've installed more than one c-band system by siting UP the center polar mount, and aiming it for when Polaris (North star) is in the bore site at the proper time of night for the location.

If you do this carefully, you'll be almost dead-on very quickly.

I used this technique when I set up my 8.5 ft Birdview last winter, and had excellent results.

I used a piece of conduit to sight Polaris. The conduit was attached to the dish, exactly parallel with the elevation axis. To get my sight tube to the correct elevation for Polaris, I used a digital inclinometer and adjusted the elevation axis to set the sight tube to my latitude. I then rotated the dish on the pole to get Polaris in the sight tube.

Moving the digital inclinometer to the elevation axis, I adjusted the elevation axis to the correct number for my latitude. The built in declination was about right for my latitude, so I left it as is.

Running the dish west about 1 degree to 107.3 (my southern most satellite) Anik F1r came booming in. I tweaked the elevation a bit, but wasn't able to make much improvement. I then headed east to check the tracking and things where looking good until I got to 55.5W where I could tell the dish was starting to fall off of the arc a bit. Continuing on to 37.5W I still had signal, but much weaker. So I rotated the dish on the pole a bit to peak it up. Checked the tracking through the whole arc and it looked good.

A few weeks later I put a Ku Band feed on the dish and the tracking, while not perfect, was pretty good across the entire arc.

BTW, Polaris is not exactly at the North Celestial Pole, so I used this web page to find when it was either above or below the North Celestial Pole. For best results, avoid doing the alignment when Polaris is east or west of the North Celestial Pole.

http://www.trutek-uk.com/takahashi/polarisfinder1-2en.htm


A few photos

 

[Cham]

Could allways use a polar scope for an equatorial mount (telescope mount)... if you have one kicking around... That way it compensates for the Polaris offset no matter what time of the (night) you set it up.
I have set up my polar mount dishes this way too when I didn't have a level that worked.

Another thing that can mess up alignment across the arc is the pole bending... it will bend more at lower E/W azimuth than when the dish is more balanced pointing at your southerly satellite. My 10' dish has a 5" diameter steel pole with 3/16 thick wall. It bends about 1/2 a degree at each end of travel. I set it a bit high on the southerly sat to compensate, maybe 0.25 degrees. I added some bracing that stopped some of the flex but did not eliminate it. Some will fill the pole with cement to make it more rigid. Maybe that would help too?

 

[N6BY]

..
BTW, Polaris is not exactly at the North Celestial Pole, so I used this web page to find when it was either above or below the North Celestial Pole. For best results, avoid doing the alignment when Polaris is east or west of the North Celestial Pole....

Yes. According to Wikipedia, Polaris is 45 arc seconds (or 3/4 of a degree) off from the true polar axis. You can compensate using a digital level if you know which direction Polaris currently is from the true polar axis.

 

[primestar31]

You guys are WAY over complicating / over thinking this. I'd rather be only a possible 3/4's of a degree OFF dead South, then hunt around for 3 days trying to get my polar mounted dish aimed and locked down while guessing and having no clue where it's really aimed. Granted, once you've installed a few c-band dishes it will be rare to need to do it this way. But, sometimes a location can really throw off your inner compass, and this is a great alternate way to get it done.

Just having everything else set properly for your location, and the mount tightened almost all the way down, and sighting in Polaris up the center mount axis can get you set very fast. All the rest is just tiny details from there.

p.s. 5" pole or NOT, if it's bending, you need to FIX THAT instead of just compensating for it. The problem with compensating, is every compromise induces more error, until you have a huge mess. I've doubled up poles, or used Schedule 80 pipe instead of Schedule 40 in certain cases, such as huge heavy fiberglass dishes.

 

[N6BY]

You guys are WAY over complicating / over thinking this. I'd rather be only a possible 3/4's of a degree OFF dead South, then hunt around for 3 days trying to get my polar mounted dish aimed and locked down while guessing and having no clue where it's really aimed. ....

We are not talking about due south, but rather the axis of rotation. It would almost be like having the pole in the ground tilted 3/4 of a degree off from plumb.

 

[primestar31]

We are not talking about due south, but rather the axis of rotation. It would almost be like having the pole in the ground tilted 3/4 of a degree off from plumb.

Sigh... You can lead a horse to water...

Follow what I mean, even if I didn't use the exact proper words.

Dammit Jim, I'm a doctor, not an engineer! lol

 

[N6BY]

Polaris is not going to help if the declination is way off. Not trying to over-complicate this, just stating a fact.

So lets forget Polaris, the easiest way IMO is a digital inclinometer (a.k.a. Laser Level). You can use it and a compass to adjust both the rotation axis and declination. I'll offer it to the next person who gets stuck setting the correct elevation on a prime focus dish.

 

[gpflepsen]

The ONLY thing Polaris is used for is setting the azimuth of the mount. Other tools give elevation AFTER azimuth is set.

 

[Cham]

Agreed we've gone off on a bit of a tangent here, but I think the point of using Polaris is not really to line up your dish properly, but to check your elevation angle if there may be an error in calculation somewhere along the way and it's not working. If your polar axis is not lined up close to Polaris something is off in either azimuth or elevation. These new fancy digital levels are extremely accurate (if you have one of decent quality) for setting up your mount.

 

[lost_mesa]

The ONLY thing Polaris is used for is setting the azimuth of the mount. Other tools give elevation AFTER azimuth is set.

Correct. Only used to set azimuth. Better than a compass. The inclinometer is used for elevation.

 

[gpflepsen]

Azimuth is the toughest thing to get right by measuring. Compasses have magnetic "variances" (not going to say declination and cause confusion anywhere) and can give 5-10 degree errors due to surroundings.

If you have line of sight, Polaris could help.

You could always look up the sun azimuth for the time when it's @ 180 degrees. Use a long pole held vertically to cast a shadow back to the dish to establish true South.

I put a big rock 70' away from my dish location to mark South, once I found it.

 

[Titanium]

For most of us working during the day, the sum provides a better reference. To confirm my compass reading, I prefer to use the sun location. This sun position calculator on my phone (Mr. Sun) provides sun position for any location or time.

For example, today at 1:05pm local time the sun will be directly south. Using the pole shadow, I can mark the ground behind the pole and sight a landmark or plant a marker in front of the dish that aligns with true south.

As long as the sun is out, I can use the pole shadow to establish any azimuth or elevation reading at any time of the day with 100% accuracy.

The Stanley level app is one of my favorite smart phone apps. Take 10 seconds to calibrate, and it is extremely accurate!

Edit: gpflepsen beat me to the post...

 

[Babadem]

Never used the Sun as a reference point for dish installation before. Learned something new today! Thanks to Titanium.

 

[JFOK]

Hi All,

Here's an update.
As tired as I was after work this evening, I went out and took advantage of the late sunset...8:18 here.
I was able to find satellites starting with 55W all the way to 99W before it started getting too dark to see what I was doing.
Will go back out tomorrow evening if I can and see how far to the west I can go. When my dish was 20 feet up I was able to get down to 131W. Don't think I'll do that well this time, but will be interesting to see what the difference in height allows.

 

[JFOK]

Hi All,

If all goes well on Sunday after a final check of the arc, I will reinstall my microHD and ASC-1 in the "man cave."
I will have to do some rewiring, but that for me will be easy compared to all the frustration I went through to get this dish up and running.
This will also mean the end of operational duties for my DSR 920 that served me so faithfully for 16 years.
Its almost as if I'm taking it off life support. Once I unplug it, the original battery will fade to non existence as will the unit ID.
I will keep it as a back up dish mover should the need ever arise.
Thanks again to all of you for your patience and helpful guidance.
Once again a BIG thank you goes out to Michael (KE4EST).

John

 

[Jw2016]

This is how I got my 10 footer up all by myself.
View attachment 111265 View attachment 111266 View attachment 111267

Is that your current setup?. It's freaking awesome and good job with your getting your satellite dish farm going. I am jealous!

 

[RT-Cat]

First thing, sorry for the l-o-n-g delay in an answer. With Summer so short in Michigan, I have to get tons of stuff done while it is warm. I hate snow(crap)and cold. I had to work in the cold years ago building power lines and that froze me forever.
Yes, that is my current set up.
Thanks for the nice comment.