Cheap, motorized two axis mount -

[ZandarKoad]

I'm looking for a two axis motorized mount that does NOT track the geostationary orbit. That is, I'm looking for a mount that I can rotate left and right without altering the elevation. Then I'd also like to manipulate the elevation without altering the azimuth. I know a regular OTA motorized mount would work good for the azimuth, but not sure how I'd get the elevation motorized.

Does a system like that exist? ... for cheap ($100 ish)?

 

[gpflepsen]

You could always replace the elevation fine tuning turnbuckle (if equipped) with an actuator and use two positioners to run two axis. You may need to fabricate mounting locations for the new actuator, but that would be relatively easy with a welder and basic tools.

 

[Magic Static]

The MoonBounce dish uses a custom made mount like that

 

[Martyn]

You're looking for an Az-El rotor. They exist, but not for $100.

There are commercial mounts for satellite dishes, but if you want to do it cheaply and are OK with manual control, I can't think of anything lower cost than a couple of TV antenna rotators (one mounted horizontally, one vertically). I don't know how much torque they would deliver, especially for a large dish.

We've also had success using a heavy-duty CCTV camera mount to turn an 11-element yagi for 2m EME, but that required a homebrew PC interface/controller.

Here's a ready-made one for amateur radio satellites:
http://www.yaesu.com/indexVS.cfm?cm...B819EE02831F3FD5B8&DivisionID=65&isArchived=0

What are you trying to turn and what's the application? Knowing that would help.

 

[ZandarKoad]

It's for pointing a wifi cantenna / parabolic dish combo. At most, it will be moving a 76cm reflector, but probably a slimline. So no high torque is required. It will be mounted high up on a tripod on top of a two story house, and I'd like to reposition it from inside.

However, after doing the math, it looks like the elevation will have a maximum variance of less than 2 degrees to hit all possible wifi spots. It may not be worth it to even motorize that. I could probably set it and forget it. (The closest wifi spot is more than 1000 feet away.)

 

[Anole]

You might review the beamwidth attainable at 2.5ghz with a 76cm dish.

 

[ZandarKoad]

You might review the beamwidth attainable at 2.5ghz with a 76cm dish.

From my research, the reflector size is not a consideration determining in the wavelengths attainable. The reflector isn't a part of the receiving antenna, it just ... reflects it. The cantenna at the focal point will need to have very specific dimentions based on the 2.4-2.5ghz wavelength's being brought in.

 

[primestar31]

A Pringles can works perfectly as a Cantenna. You need a larger dish such as a Primestar elliptical to give it proper full illumination. I used one for 5 years, 300ft + through a woods, and worked fine 95% of the time.

Or, you can build a Biquad feed, and it mounts perfectly on a 20" Dish antenna inverted to point better for that type of service. My testing at my location actually showed that a properly built Biquad worked better, (and is more stealth) but a Cantenna has a "tighter" beam.

http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/

 

[FaT Air]

A regular tv antenna rotor should do just fine. I wonder why you also need elevation? Just point it to the horizon.
Your beamwidth, at 2.4Ghz, will be much greater than the <2 degrees the dish exhibits at 12Ghz. If the feed is a cantenna, I'd just mount the dish inverted, so it doesn't fill with rain/snow.

 

[Anole]

From the very comprehensive Engadget article:

...The two APs on channel 1 are a bridge between town A and town C which is located 2.6 miles directly behind the dish.

Gotta love that directionality! :up

 

[primestar31]

From the very comprehensive Engadget article:


Gotta love that directionality! :up

Read again.

They didn't mean their ap dish was pointed at it right then, just that those particular site ap's were located behind the dish at that specific time period when they were pointing at an ap in front of the dish... If they wanted to point at that one behind the dish, they would of course spin the dish around to point at them...

 

[updatelee]

You could always replace the elevation fine tuning turnbuckle (if equipped) with an actuator and use two positioners to run two axis. You may need to fabricate mounting locations for the new actuator, but that would be relatively easy with a welder and basic tools.

Thats not a true two axis though. At your due south then it would be, but as you approach your max east/west then the elevation adjustment would be more of a skew adjustment no longer elevation.

UDL

 

[ZandarKoad]

A Pringles can works perfectly as a Cantenna. You need a larger dish such as a Primestar elliptical to give it proper full illumination. I used one for 5 years, 300ft + through a woods, and worked fine 95% of the time.

Or, you can build a Biquad feed, and it mounts perfectly on a 20" Dish antenna inverted to point better for that type of service. My testing at my location actually showed that a properly built Biquad worked better, (and is more stealth) but a Cantenna has a "tighter" beam.

http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/

If you were comparing the Biquad to a pringles cantenna, then yes, I'd expect the Biquad to outperform. The pringles can is considered, by nearly every source I could find, far too small in diameter. Also, the length is not ideal. I was trying to find a very long, very smooth can, but ... It's impossible to even special order those things. Instead, I'm probably going to go with a length of aluminum duct work. It's very smooth, very long, has a good diameter at 3", is readily available, cheap, workable, and resists corrosion. The only downsides I could see is 1) the locking ridge which runs the length of the can and 2) how to 'end' the can... I'll probably cut a circle of aluminum and use some JB Weld to seal it on the end. It may not be perfectly microwave tight, but I figure it's close enough, and better than a ridged can bottom.

I'm not so sure the beamwidth is all that large. It's coming out of a cantenna remember. That's one of the reasons I chose a cantenna as a feed rather than the biquad - I'd like the tightest beamwidth possible. I figure it would pick up (and cause) less interference that way. My cantenna is going to be about 24" long, so that should give a real nice tight beam. At least, in my own little mind.

 

[FaT Air]

The 'systems' beamwidth is determined by the frequency and the width of the dish, not the beamwidth of the feed. That would be akin to the feeds F/D ratio.
The cantenna beamwidth should be wide enough to illuminate the entire surface of the dish. That said, the coverage should roll off towards the edge, no sense in spilling excessive signal out past the edge of the dish.
If your feeds beamwidth is narrow enough to only illuminate a small portion of the dish the only result is decreased gain. Signals from a distant source bouncing off the outer surfaces wouldn't end up in the feeds throat.
All that said, seem to remember many pages that documented better performance utilizing a 'pizza' dish with the bi-quad feed.
Maybe your cantenna alone would provide the performance you need(no dish).

 

[primestar31]

http://people.wallawalla.edu/~rob.frohne/Airport/Primestar/Primestar.html

http://www.trevormarshall.com/biquad.htm

http://www.cantenna.com/ <<<< this works VERY well, if you can find one anymore.

http://discuss.pcmag.com/forums/thread/1004346021.aspx

 

[ZandarKoad]

Thanks for those last two links, I've never seen those before. Odd how that cantenna page is still up despite being out of production. Apparently it's only a 12 db gain... other designs are in the 25-30 db gain range. Also, the author of the article in the last link reports that the 'super cantenna' is a poor substitution for the original 'cantenna' that they were producing.

I think I need to stop reading about this stuff and just do it.

 

[Pixl]

I think I need to stop reading about this stuff and just do it.

Just what I did. Take a look at my posting in C-band dishes.
http://www.satelliteguys.us/threads/281859-9-FT-Steel-Dish-Project?p=3195022#post3195022

 

[Anole]

Now we're talkin'

Just what I did. Take a look at my posting in C-band dishes.

This is so right!
9' solid BUD, 3" copper pipe, dd-wrt router (and mounted on the dish for short coax run!)
That's how it's done. :up

I explored such a configuration before I joined SatGuys.
Was leaning toward a helical antenna, though.

Only thing I might do different today, is mount a USB wifi device at the focus of a dish.
No coax required, and easier to power and waterproof than a whole router.
(not that I didn't explore multiple ways to power & waterproof one at the top of my 32' telephone pole!)

 

[Pixl]

Only thing I might do different today, is mount a USB wifi device at the focus of a dish.
No coax required, and easier to power and waterproof than a whole router.
(not that I didn't explore multiple ways to power & waterproof one at the top of my 32' telephone pole!)

I considered that approach, but don't know how far a usb cable will work. This install is 110' from the house, so I figured I would have to waterproof and mount a whole computer somewhere near the dish. The distance is not a problem for a cat 5 run, and since only 4 of the 8 conductors are used for Ethernet, you can double up the last 4 and make your own power over Ethernet setup. The wall wart is in the house.

 

[Magic Static]

I used a USB to cat5 adapter to hang a usb wireless adapter outside for better reception. Sealed it up in a powerade bottle. Was about a 60 foot run of cat 5.