View Full Version : Parabolic Radar Dish

11-15-2007, 04:43 PM
I've looked and looked... and come to the conclusion that I'll have to do it myself.:genmad:

The idea is to have a small parabolic dish, either functional (requires alot of calculations!) or just for show, that will be directional and/or rotate. I checked through numerous websites, looking at plastic space models, checking real antennas, scouring misc. parts bins etc. and found NOTHING that would be suitable. The closest I got was a real mesh antenna from www.antennasystems.com (http://www.antennasystems.com/) that is about $90 :eek: and about twice as big as I'd like - about 11 inches wide by 4 or 5 inches high, half a pound, and WiFi at 2.4 GHz. Very nice, but too big and too expensive for my tastes. (Though it would be WiFi...)

OK, I've got a good supplier of 4x10 aluminum sheets... but my tinsmithing skills are probably woefully inadequate. IMHO a bad execution will look worse than no dish at all.

A decent dish should be stiff but light, and should not look BULKY. I figure a good size for most bots would be no more than 6 inches across (from 3 to 6 would be best).

I thought a plastic colander (spaghetti strainer) with a horizontal mesh could maybe be cut to size and spray-painted. One with a respectable curve in 2 dimensions (L to R, and top to bottom) could maybe be found in a kitchen gadget store. Of course, this would be a non-functional type, but boy-o-boy would it LOOK cool. (And ain't that half the battle?);)

I have a few mini microphones, and thought about mounting them in a half shell, the kind that contain small toys, the ones you find in a supermarket bubblegum coin-op machine (25 cents or so). Cheesy, but might work for a small mic.

Does anyone have any better ideas on how to do this?:confused:

Note: see my blog entry titled "Regarding Radar Dishes..." - I may have stumbled on a cosmetic solution.

11-20-2007, 11:24 AM
Man kdwyer, you weren't kidding! I just looked around online and couldn't find crap except for plastic radar dishes:(

Sorry, you already far surpassed the only ideas that I had with creating you're own. There are a ton of hardware peeps in this community, so hopefully someone else can share a bit of their knowledge.

BTW, I updated your post with the correct URL. Feel free to add any of your pics to your gallery too:D

11-20-2007, 02:48 PM
I couldn't even find plastic radar dishes!
As per my blog entry, I have cut out the vent from an old VCR case. It has horizontal rectangular slots alot like the ones on the real antenna from AntennaSystems. I don't have the metalworking tool to smoothly roll this sheet into an arcing bend (forget the name) and I'm still thinking this over. This, when done, should look bitchin. I hope. I only wanna do this once since it is a pain in the ass and I only have so much old equipment lying around. (Liar!)
OK, it won't work as a real antenna... but I did some quick calculating, and my dimensions aren't too far off. Something about half the wavelength... and then comes the arc. Adding that into the calcs... ugh. My processor hurts.
And thanx for correcting the URL. Some days I can't even cut 'n paste right.
And I'll post the next phase of bending as I get it figured out. A flat panel works, but an arcing one is better.

12-05-2007, 10:12 AM
Check this out, it maybe what you are looking for. It's not a colander, it's a steamer, and it folds open and then closes. With a little work with a servo this would be cool and very cheap (cheap is good). It's only $6.00 and also I have used it for a para dish with a small condenser mic and it worked great. Here are some pics for it. http://www.fantes.com/steamers.htm

12-05-2007, 10:59 AM
Thanks, Tymtravler, this looks excellent. My one concern with this particular item at this time is one of scale. It is about twice as big as I need for Otto, it would dwarf him! For a larger size bot, it does look great, and I've bookmarked the site for future reference. Now if they made a mini, about 5 inches diameter when opened...
I made a cruder one out of a VCR case vents (check the gallery for 'antenna') which ain't half bad, but this one is way cooler. Now I suppose I'll have to build a bigger bot to go with it...

12-30-2007, 04:01 PM
hey there, i know this thread is a bit old, but i just joined and i thought i'd throw in my input (i've had quite a bit of antenna design experience). the first thing to note is not all things that look like dishes are good designs! in fact, a poorly designed dish will cause signal strength cancellations from bad reflections. out of curiosity, is there a reason you want a dish as opposed to any other sort of directional antenna? there are several directional antenna designs that are a lot easir to build. as an example, a yagi-uda (http://en.wikipedia.org/wiki/Yagi_antenna) or using a corner reflector (http://en.wikipedia.org/wiki/Corner_reflector) or a waveguide are a lot easier (and cheaper!) to hand-build. if youre designing for wifi, i've written up a "how to build a wifi cantenna (http://www.eskibars.com/projects/cantennaguide/)" page on my site (http://www.eskibars.com/).

if you absolutely must use a dish, use something that holds a little more of a naturally-defined parabolic shapes. woks and bamboo strainers are cheap and have a pretty good shape. if you decide on one and need help with design guidelines, let me know.

12-30-2007, 04:38 PM
Hi Eski
This is a completely non-functional addition. It is purely to make Otto look hi-tech, therefore a standard round dish or dished rectangle (slotted type) is best. Anything that actually works would probably look alot more mundane.
Is there a directional antenna design (434 Mhz or so) that works, as well as looks good? A simple wire antenna of proper length would work, but I gotta have that 'funk factor'.