Rx antennas

[Wesleys Custom Graphics]

My futaba rx antenna has a short and needed a new one. A friend gave me several but the length is not the same. Do they have to be a certain length?

 

[derek owen]

I asked similar question few weeks back, all to do with wave length basically the exposed tip is the working part (25mm) which is stripped back if this tip is shortened then loss of range, the length of the overall wire doesnt play any part... except for getting the 25mm tip into a good position outside the hull and away from any carbon shields and the like.. im sure there will be more in depth replies...

 

[Mike Hughes]

What Derek is talking about is 2.4 receivers. If your running 27, 72, 75 band receivers then length is different for each one. The receiver is tuned to the length of wire. If you shorten or lengthen it, you are detuning it. Do that enough and you will lose signal inputs. Best to check with manufacture on length.
Mike

 

[Wasted wages]

I must have been very lucky in the past then with 27/75 radios..

I can't tell y'all how many antenna's that got clipped off on riggers by props.

I always ran as much of the lead out of the radio box thru a bruline tube and then doubled it over. Occasionally the wire would slip and get cut off half length. Never lost radio,

I also cut the wires short and soldered them to a brass fitting that had a solid piece of piano wire attached with a setscrew. Never seemed to make a difference on reception..
Always passed a range check. Like I said, must have been dumb luck !!

 

[Mike Hughes]

I had a buddy use those deans load base antennas. He was always hitting the beach because of range. I finally went over to his stuff and grab one of his receivers. They had that quick connect piece so the receiver could be remove from radio box without removing the antenna. I was pulling on the connector and it slid right off the wire. He never check those. The antenna wire was only about 3" long. It would connect and disconnect during vibration of running boat.

Wasted,
The good thing about your scenario is the percent of antenna remove was little compared to the complete antenna. The whole wire from the PC board to end is the antenna. They are 1/4 wave tuned. I seem to remember them being 28"ish for one of those bands. It might be 27. The 75 and 72 were shorter. Maybe 18 or so. With 2.4 you only have that 3/4 inch or so of exposed wire that is the antenna. Easy to cut that in half and you going to have issues. You probably lost about 10%. You did lose range but not enough to affect you running around a normal course. I use to take a straw tube and wrap the wire around it and tape it up. This shorten the wire without losing the tune. You had to make sure that the coils did not cross over each other. That would shorten the range as well. These problems are not really an issue any more since 99% of us have switched to 2.4.
Mike

 

[Grimracer]

Wes.. if its your 2.4 radio system you can change the antenna.. but... not all of them without sending them in. if its a 203 you will have to send it in.. if its a 304 or 324 you can change them your self.. NOTE.. in our part of the hobby there are only two antenna lengths available. so.. it would be the normal one (I dont know the length off hand) or the 400mm unit.. if your buddy gave you something else PASS on it.. Grim

 

[Wesleys Custom Graphics]

I forgot to mention that it was a 2.4. I thought it was bad because I could not get continuity but when I tested a new one I could not get it with that one either. I could get it all the way up thru the shielded part but not at the tip. Kinda weird.

 

[Mike Hughes]

It is a coax wire. A center conductor surrounded by a plastic insulator and a shielded on the out side of that.. Just the same as you home cable but smaller. The radio signal bounces back and forth from the shield to the center conductor. You also want to not have it kinked. This will stop the signal. Nothing tighter than about a 1/2" radius.
Mike

 

[Wesleys Custom Graphics]

So the center conductor does not go all the way to the tip? Past he shielded part?

 

[BobLondress]

The center conductor that goes past the shield IS the antenna. Its a quarter wavelength at 2.4 ghz or about 7/8 "