Receiver antennas, how do they work?

[retiredflyer]

Do the external wire antennas on receivers act using their whole length, or is the only part that is effective the exposed piece at the end? Just wondering if the coating on the antennas does, or does not inhibit the signal. It's basically just a wire with a 1 inch stripped end. Is the rest of the covered 4 inches doing anything too as far as receiving a signal or does that wire coating actually prevent any signals.

[doctormike]

The antenna receives a signal through the foam, as well as the wire insulation. It's the full length receiving a signal. Also, a transmitters antenna sends a signal from its full length, which is why the antenna should be positioned so it sends the signal from its side, not the end. This is true with a moveable antenna such as on a DX6i. On a DX6, as I understand, the antenna is inside the handle, so it is always perpendicular to the airplane. Doc

[wpmay]

The references I have read indicate that the proper 2.4 GHz antenna length is ~32 mm (1/4 wavelength) meaning only the bare exposed part of a typical 2.4 GHz RX antenna wire is actually the antenna. I'm no radio expert so I could be wrong. The wire insulation wouldn't really inhibit reception anyway so I'm not sure it makes any difference in practice. However, with 2.4 GHz dual antenna RXs, I think it's most important that you place the two bare wire parts at 90 degree angles and not in the same plane (that is spacial area....obviously you want them in the same aircraft :D:D:D).

Bill

[OV10]

In my early years prior to retirement and being a contracts manager I was a microwave engineer on an F-4 microwave receiver program called 'Wild Weasel' (late 70's) so this thread immediately caught my attention. Doc, sorry to say but your response is incorrect and Wpmay's is the most correct not so technical explanation for the microwave propagation design lengths on our radio's using the 2.4 technology.
On the DX6 the handle is not the antenna whereas the cylindrical probe at the top of the transmitter is where the antenna is contained.
The antennas being used on radio control RC is of a monopole design whereas the length is a 1/4 wavelength of the frequency whether it be of the FM or microwave frequency bands. The 1/4 wavelength was electrically derived to reduce the physical length of an antenna without introducing undesirable harmonics of the frequency. Lower frequencies like FM have a long wavelength and microwave has a very small wavelength. The longer the wavelength the farther it can travel with less power. That is why the 27 & 72mHz radios of prior years had such long antennas(like 3 ft) compared to todays 1-1/4 inch.
Doc in all fairness to you, your response was more descriptive of the FM frequency bands where the full length of the antenna was used. On todays receivers if the antenna is longer than the 1-1/4 inch length, the base portion of the lead is a non radiating section that is designed to get the actual antenna somewhat clear of other interfering devices like maybe servos or whatever(That should answer your question Retired).
So that is just the tip of the iceburg regarding propagation practices whereas more in depth knowledge can be gleaned from other more technical sources.
Best regards,

[wpmay]

OV10, thanks for the additional information!

Bill

[doctormike]

I stand corrected, however, I want to do some research on the DX6 antenna. I know the probe at the top is a portion of the antenna, but, I have read that the antenna is also in the handle. True to my nature, I want to get the facts. I use Spektrum receivers. There is no bare wire antenna. There is a short antenna and a long antenna, and the two are to be 90 degrees to each other. Doc

[xviper]

I have used receivers of various brands and so far, all have worked flawlessly. I started with Spektrum, both the ones with the satellite Rx and ones with just the little stub and long antenna. Of these, some of the long antennas were just a straight wire and others have had that little lumpy thing near the end. Then I've used the Orange Rxs from HobbyKing, but only the ones with the satellite. Lately, I've started using the Lemon brand of Rxs. Till now, they've had the satellite but I'm about to try the latest ones with the dual, longer wires. Lemon calls them "diversity" antennas, whatever that means. Some have been for DSM2 and some have been for DSMX. They all have worked with my DX8 and now with my DX6. To throw another oddity into the mix, I've also used the Spektrum "park flyer" Rxs on small, light foamies, which I have flown a ridiculously far distance away, way farther than the manual would suggest. With the exception of the "park flyer" Rx, I've used all of these in sailplanes, which have been flown to beyond visual line of sight and they have all performed without incident. (Return to Home has always brought them back.)
I have no idea how these things work but I am amazed at how far technology has come in this area.
Oh, and one more item of interest ................... I have a UMX Radian as does several others at my field. A couple of us have flown these things up over 500 feet, along with the other full sized Radians. Don't know what kind of antennas are on the little Radians, but they are amazing.

[WintrSol]

I stand corrected, however, I want to do some research on the DX6 antenna. I know the probe at the top is a portion of the antenna, but, I have read that the antenna is also in the handle. True to my nature, I want to get the facts. I use Spektrum receivers. There is no bare wire antenna. There is a short antenna and a long antenna, and the two are to be 90 degrees to each other. Doc

As OV10 explained, our 2.4GHz radios use 1/4 wave antennas, both for transmit and receive. A 1/4 wave antenna works best with what is known as a ground plane - a conductive surface through which the antenna protrudes, and provides a reflected image of that antenna. If you remember them, CB antennas worked best when placed in the center of a metal car roof, and not as well when clipped to the window frame. The handle of the DX6 could perform some of this function, if it is near enough to the radiating portion of the transmitting antenna, but likely not. Under the insulated part of the antenna is a woven shield, which becomes a reflection of the exposed portion, so also, usually, is a multiple of the 1/4 wavelength. For best performance, the antenna, including its shield, is matched to the transmitter or receiver active circuits, which is why you can't just change the length at random.

[retiredflyer]

Super responses everyone, thanks. I was hoping that if I couldn't really get the two wires completely stretched out inside the plane body, I could try to get the ends perpendicular to each other on opposite sides of the fuselage. I was just concerned that the blobs of CA or adhesive used to secure them along their length was inhibiting the reception. It would appear from your answers that it wouldn't.
Appreciate the radio and frequency lessons.

[doctormike]

I use E-6000 cement to hold my antenna's in place, as well as my receiver. It makes them more easily removed, if needed. Doc

[WintrSol]

Instead of putting glue on the wire, I usually use either hinge tape (Blenderm) to hold the wire in place, or glue a small plastic tube to slide the antenna wire into, depending on the model. That way there's little risk of damaging it if I have to pull the receiver out.

[boomer108]

I use packaging tape to secure my antennas. Holds well and doesn't hurt the foam when you remove it.