Slashdot Mirror
Alternative Uses For an Old Satellite Dish?
ya really writes "My family has one of those BUDs (Big Ugly Dishes) sitting in their back yard still. The other day they asked me if I would take it apart for them. Aside from simply recycling it, I was wondering if there are any alternatives for its use. It was one of the last made before DirectTV and Dish took over satellite broadcasting, and even has a digital receiver. I'd say it was made around 1996."
or cover it with tinfoil to run a sterling engine??
Go over to lyngsat.com and see what you can see. Satellite TV is far more than what the media companies are willing to sell you.
Get a different receiver and you can receive weather satellite data, etc., directly. Hook up with your local ham radio group for more info.
Uhhh, actually... that is a really good idea. Fantastically good.
Nothing would get you more geek street cred than having your own DeathStar in the front yard. Extra Points if you mount it in a container that allows you to aim at various neighbors with a high powered green laser inside of it.
You'd need an elliptical dish for that. Satellite dishes are parabolical.
The curved dishes make decent ponds for birds to splash in. Cover the edges with rocks or something else decorative to hide what it really is.
Are you sure parabolic dishes are resonant? I say bullshit.
How can you use a BUD for long distance? Wind load at the heights needed to avoid fresnel zone problems would be freaking huge on a BUD! The biggest I've seen is a 30dBi 59" antenna and even that I don't think was usable on most towers as it had a loading factor of 100 lbs at 120mph.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
don't you know how dangerous it is to post a link to xkcd on slashdot? what was originally just hours of wasted productivity has now increased exponentially. i'm still not doing anything tomorrow right now!
not only is time travel possible, it's irrelevant.
Wrongo!
The only difference between c-band and ku-band dishes is in the feed-horn. because KU band is a much higher frequency, the aperture is much smaller, and thus a different sizing WG fitting is required to mate with the LNB. Of course, there is always the issue of polarity as well, linear and circular polarized feeds have different setups.
The dish itself is just a big surface area to collect signal and bounce it into the middle. You can get c band ku band l band, and pretty much all microwave frequencies (hence the polularity for ISM hack-jobs)
the above is my personal opinion and does not necessarily reflect that of the little voices in my head
Since little USB wifi and bluetooth adaptors are so cheap, you could mount one of those at the dish focus. Make a wooden block to hold in, which replaces the LNB.
Although the reflectors for either C or Ku band dishes would work fine, it should be noted that the FCC regulates the effective radiated power. Check out FCC EIRP (equivalent isotropic radiated power) Limits.
The reference is an isotropic radiator... like having a point source radiating energy equally in ALL directions (up and down as well as the horizontal plane. A vertically oriented half-wavelength dipole has 2.15 dB gain over an isotropic radiator. If vertical, it radiates equally in all directions horizontally, but drops to nothing straight up and straight down.
Many have used a dipole as an alternate reference since it the lowest gain and most basic antenna normally constructed.
The EIRP rating is basically the amount of power it would take fed into an isotropic antenna to equal the signal produced from the gain (focusing effect) of a directional antenna. Some get confused by antenna gain. It doesn't give us more power than a transmitter puts out, it just concentrates the signal in a desired (hopefully!) direction at the expense of other directions.
The FCC rule differ for point to point versus point to multipoint WiFi. Point to multipoint the limit is 4 Watts effective regardless of antenna gain. (36 dBm, m being mw or milliwatts) A 100 mw card (20dbmw) feeding a 16 dBi gain antenna would produce 36 dbmw EIRP if there was no cable loss. If 3 dB was lost, it would take 200 mw into the cable to compensate (23dbm -3dB + 16dBi = 36
Point to multipoint starts at the level for a low gain antenna, but only requires a fairly small reduction in transmitter output power as higher antenna gain is used. So the maximum allowable signal does increase quite a bit with higher gain antennas.
Since things are pretty close to line of sight at 2.4 GHz, a huge dish near the ground (and not pointing up in the sky) isn't likely to do nearly as well as a smaller one up above the clutter. So most C band dishes (usually 2 to 4 meters across) are too big for most situations. Gain is probably best estimated by comparison with commercial dishes of the same diameter and frequency.
Allowable power is likely different in other countries. Your mileage (kilometerage????) may vary