Aerial advice please

[Andy]

Could anybody advise us on the best place to mount the aerial on Push n Shove please?
Weve got hardox sides and ali top and bottom and it runs upside down as well. Were using a Futaba 2ch transmitter. How long should the aerial be? If it was mounted on the sides whats the best way to protect it from being hit in battle? Weve looked at the link on an earlier thread but its like talking in another language to us!!
Wed appreciate any help (in very simple terms please!). Thanks.

[maddox]

If your machine is full metal outside, the antenna is effectively in a Faraday cage.

Even if it could recieve a signal inside, all the interference produced by the motors and so will stay in.

Rule number one. DO NOT SHORTEN THE ANTENNA WIRE ON A RECIEVER. Not unless youre VERY sure of yourself.
Rule number 2. THE ANTENNA MAY NOT TOUCH METAL

Several solutions are possible.
Bringing out the antenna with a shielded cable in the robot is the oldest trick, but the most tricky one too. Lots of good tries, but many failures as well.

The trick now used by TAN and Hard, the reciever itself is mounted in a pocket in the armor, shielded by thick polycarbonate on the outside, and the antenna is run out.
In Hard the inside of the pocket is a part of the metal armor. Shielding the reciever from interference from inside the robot.

These 2 systems leave the antenna exposed.

For a more protected antenna the Hannibal solution is possible.
Again mounting the reciever as close to the outside, under heavy armor and run the antenna out. But Sandwiched between 2 layers of plastic, like Polycarbonate or HDPE.

drill a hole in the top piece of armour above your reciever, put a rubber grommet around the edges, OR put tape round the exposed metal edges of the hole, poke the aerial wire out.
run a line of tape across the top of the robot, and lay the aerial wire over it... then tape over the wire so its stuck down flat on the surface..

also a good idea is to stop some of the source of interference by putting a small capacitor across the motor terminals (there may be one there already... if you arent sure bring it along to a robot event, and theres bound to be someone wholl do it)

this gives an unprotected solution, itd work...
not many robots bash the top, have to be a lucky axe hit to sever the wire.. try it first to see what sort of range or interference you get.. if it doesnt work then move on to shielded wire... (TV aerial cable) to shield it from radio signals as it leaves the chassis.. this does involve desoldering the aerial wire, so unless you are happy with a soldering iron dont do it.





(Message edited by killercarrot on October 02, 2006)

[jamesb]

boat ariel.
see http://www.technobots.co.ukwww.technobots.co.uk for these
i now use them on all my robots.

[Andy]

Thanks for your advice. We did something similar to Robs suggestion at Doncaster but ran the aerial through plastic tubing and taped it down to the top of the robot. Trouble was, it wouldnt pick up a signal once it was in the arena!
If we use boat aerial, do we just desolder the existing aerial and replace it?

[geeza]

No just have the boat aerial it bolts through your top armour and then there is a screw down connector that the reciever wire goes into.

[jamesb]

what he said

(Message edited by jamesb on October 02, 2006)

try a boat aerial they are dead cheap.
if you get interference again you might have to desolder the wire from the reciever to the and replace with shielded wire... I use old coax computer network cable...
On your box shape robot, you may have to bend the aerial flat against the body so it will run inverted.. depends on clearance..
and again we are back to taping things flat...
look at the pic on my profile... see the bit of tape with the arrow on it.. thats my boat aerial taped to the lexan..



(Message edited by killercarrot on October 02, 2006)

[Andy]

OK, boat aerial it is! Thanks very much.