Comment by Coptaire on April 25, 2012 at 8:09am

"24dBi High gain dish antenna" for which frequency range?

For a ground station, often an omnidirectional is combined with a directional, switched by diversity, so on top of a moving vehicle, the same combination of directivity would seem a good option.

Even with such an antenna, you can loose track of your target, liken hidden by a building, and an omni antenna could save your data link.

Comment by george on April 25, 2012 at 9:41am

I don't have any bluetooth modules but I've got plenty of xbees. Is it possible to have the radio modems setup with different network ID's and simply have the telemetry data come through the RX pin and straight to the TX pin of another radio modem and finally to the modem on your laptop? The reverse would be done ofcoarse for outgoing telemetry.

Also, has anyone used a complete ardupilot mega for antenna tracking? I've got an extra one here and I'd love to take advantage of the GPS and magnetometer so I don't have to calibrate. If someone understands the coding we'd have a mobile tracking antenna :)

Hmmm....Bet that pan tilt mechanism could be printed off on a 3d printer.

Comment by george on April 25, 2012 at 9:45am

@Coptaire

I second your suggestion of using an omni directional antenna combined with a diversity receiver. Beam width is horrible at close range.

Also, most people here will want an antenna for their telemetry and video so maybe a couple patch antennas would be more ideal. Any antenna geniuses know if it's possible to pickup 900mhz and 5.8 with a single dish?

Comment by Coptaire on April 25, 2012 at 10:09am

@George

900mHz and 5.8gHz have very different propagation pattern, one being quite 'omni' (900) and the other being "line of sight" (5.8). For this reason, this wide band antenna you would wish is hardly conceivable.

We suggested to couple an omni with a diversity switch, but this omni would be tuned to 5.8, and not 900. Experimentally, you could try your omni (for 5.8) antenna with your 900 RX, and appreciate the gain, comparing to "no antenna" and "900 antenna". Should the gain be (surprinsingly) good enough to consider it, you could split the omni signal, and having one way through a 900 mHz RF filter to which you connect your 900 RX.

Am pessimistic, but antenna alchemy! ...

Comment by george on April 25, 2012 at 10:27am

LOL, antenna alchemy is exactly right! If you've seen IBcrazy's work over on the fpv forum of rcgroups you start to assume anything is possible regarding antennas.

Comment by Nicolas Larsen on April 25, 2012 at 10:39am

Great initiative! Thanks very much!

Developer Comment by R_Lefebvre on April 25, 2012 at 11:10am

@george, yeah, I have a number of industrial machines here that use slip rings and, I'd recommend not using slip rings.  Maybe if they were gold plated instead of bare copper it would work better.  But they are always causing problems for me and I'm not even attempting high speed digital communications.

Or, just use a wire down the center of the shaft, allow it to twist and... just don't fly too many circles around the ground station.

Comment by Luca Mariotti on April 25, 2012 at 12:17pm

Do you have any .dxf files

Comment by naish88 on April 25, 2012 at 4:25pm

I try to answer back to all...
@ gerorge... Data over slip rings is not a big problem, in the past I builded a device with slip rings and  RS232 flowing  at @19200 with no problems! I suggest you to buy one and give a try, and remember that antenna is never on continuous fast rotation like a radar!
@ Luca... no sorry!

Comment by Greg Fletcher on April 25, 2012 at 6:50pm

I figure that if you are using a dish you are doing long range stuff. In this case continuous rotation is not necessary. You can use a cable and you wont be flying circles around yourself, but just maneuvering at long range so not much ant. movement. Even if vehicle mounted you are more or less going in one direction and not driving in circles. If you are flying around yourself at short range then you would be using an omni. BTW they have made for years satellite TV dishes for boats and RV's that are gyro stabilized. Use a cable in the center and only allow one or two turns than have a quick reset (unwinding) when needed.

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