Balsacutter

My Feedback: (3)

I fly smaller electrics, and I'm tired of always trailing an antenna wire that's longer than my fuselage. I vaguely remember some supplier offering shorty Rx antennas, but I've forgotten who. Anyone have any experience with these?

Anyone know if they any more than just a coiled -up length? What the Hams and CB'ers call base-loaded?

- Balsacutter

JoeAirPort

My Feedback: (41)

Smiley rubber duck? I have one and there are all sort of opinions on them. I use mine on gassers and not a glitch. Got tired of bending them and then folding them. Do a search, there's all sorts of threads on them.

http://smileyantenna.com/index.php?cPath=43

exeter_acres

My Feedback: (2)

Deans micro antenna works too
http://www.espritmodel.com/accesories_antena.html

I use them in my heli's and smaller stuff.. I'm told they are fine for bigger stuff (jet guys use them.. but jet guys are a little "off" already!) but never got around to it as the regular antenna fits inside the larger fuse

JPMacG

My Feedback: (2)

I have a design for a shortened receive antenna. It takes the original 39" wire and winds about half of it around a small plastic bobbin. If the dimensions of the bobbin are properly chosen the series inducance of the coil will just about perfectly tune out the capacitance of the shortened antenna. Translation: it works well. If you're interested I will post the details. So far I have had no range issues.

JohnBuckner

My Feedback: (1)

This is one of the common arrangements used by many in the pylon community for years now where any trailing antenna portion is unacceptable.

John

fizzwater2

My Feedback: (61)

JPMacG - I'd like to see the details of your bobbin arrangement for shortening the antenna - sounds like a good idea!

Thanks

Balsacutter

My Feedback: (3)

Sounds like a good design. Love to see the details....

-Balsacutter

Flypaper 2

http://www.uoguelph.ca/~antoon/gadgets/flywire.htm. I have half a dozen of these in use with no problems whatsoever.

JPMacG

My Feedback: (2)

Ok I'm back....

I will post photos when I get a chance in a day or so.

The coil form (bobbin) is a 0.48 inch outer diameter 0.5 inch long plastic tube that I cut from an old felt tip marker. I wrapped 12 turns of the antenna wire around the bobbin, locating the bobbin close to the receiver with the unused wire extending past the bobbin. This shortens the total receive antenna length from 39 inches to about 20 inches. Secure the wire by running it through holes drilled in the bobbin or wrap with a thin layer of clear plastic tape if you like.

In order to get the desired inductance the turns should not overlap but should be closely spaced (wire insulation touching) on the coil form. This will produce an inductance of about 1.7 uH, which will cancel the capacitive reactance (about 700 ohms) of the shortened antenna.

I have used this technique with a GWS single-conversion receiver on a park flyer and with an FMA M5 dual conversion receiver on a small glow powered 3D airplane, so far without any apparent range issues. Note that these receivers have a smaller diameter antenna wire than Futaba receivers, so if you are using a Futaba receiver (I don't know about other brands) the coil dimensions may need to be adjusted.

This method is handy... you don't need to cut or solder the antenna wire - just wrap it around the coil form. I place the coil within the fuse and run the remaining wire outside or along a wing. Of course I recommend a careful range check prior to flying with the loaded antenna. Receiver antenna performance depends on many things, and while I have had good results, as they say on TV, "your results may vary".