Rx Aerials

[Tosh McCaber]

Another wee question.  For most of my general flying, I go with Spektrum receivers with no external aerials.  However I also use other Rxs with external aerials, making sure that the aerials are at right angles to each other.  These aerials vary in length, but all have the last 27mm+- portions uncovered wire, with the rest, I believe, shielded.

 

My question- is it important to just have the last uncovered wire at right angles to each other, or should the whole aerial cables be at right angles?

[Don Fry]

The last uncovered bit, is the aerial. The rest of the wire just carries the signal back to the receiver. So it’s where you put the uncovered bit that matters.

[SIMON CRAGG]

Call me old fashioned, but in my experience it is crucial to have the two antennae at 90 degrees to each other (Futaba).

 

I have seen several models come to grief with the wires just bundled in with the usual myriad of servo / lights leads in the bottom of the fus.

 

I always try and keep them away from other leads and slid into a suitable small plastic tube, glued to the fuselage.

 

 

[leccyflyer]

It's important to have the unshielded last bits of the antennae at right angles to each other, the shielded bit doesn't matter in that. Depending on the model I secure mine with a piece of tape, or a small length of plastic tube, or in a wee hole in the structure.

[Tosh McCaber]

I thought that that was the case Leccy/Don.  And that's what I've been doing.

 

Thanks all!

[FlyinFlynn]

3 hours ago, leccyflyer said:

It's important to have the unshielded last bits of the antennae at right angles to each other, the shielded bit doesn't matter in that. Depending on the model I secure mine with a piece of tape, or a small length of plastic tube, or in a wee hole in the structure.

I think it important to mention the purpose of those lengths of shielded cable is to move the active parts of the antennas away from each other to minimise the possibility of both being shielded at the same time...they do matter in that regard.

[leccyflyer]

True.

 

Tosh - don't go cutting off the shielded bit and just leaving the unshielded bit in the model, it turns out that the shielded bit is important after all ;).

[Tim Donald]

6 hours ago, SIMON CRAGG said:

Call me old fashioned, but in my experience it is crucial to have the two antennae at 90 degrees to each other (Futaba).

 

I have seen several models come to grief with the wires just bundled in with the usual myriad of servo / lights leads in the bottom of the fus.

 

I always try and keep them away from other leads and slid into a suitable small plastic tube, glued to the fuselage.

 

 

 

I have got a couple of Futaba R3106GF receivers that have only got one aerial.  2.4ghz and T-FHSS but without telemetry and branded as AirMono.  I bought them as an experiment to see how they perform since they are almost half the price of any Futaba receivers with dual antenna.  So far I they have been floorless in both power models and slope soarers.  I have chosen models that are not very precious to me just in case !!!  It makes me wonder how much marketing hype there is with radios these days.  Sure if you have a very expensive model you want the best of the best but for an every day club flyer I'm not 100% convinced that it is necessary.  The only times I have seen problems personally with 2.4ghz has been when the antenna has been heavily shielded by carbon such as in a DLG fuselage.  

Maybe I have just been lucky 😂  

Edited March 10, 2023 by Tim Donald

[Simon Chaddock]

My own view is that it really does pay to keep the aerial(s) as far away as possible from other wires or even the battery.

I have a suspicion that what works flawlessly even at a test range can cause problems as the signal becomes weak. Modern 2.4 receivers 'recover' much better than they used to. Some of my early 2.4 took 3 seconds. An awful lot can happen in that time. 😲

 

This was not such a problem with the long aerials of 35 meg. It never ceases to amaze me how it still performs with the aerial just dangling out the back.   

[fly boy3]

Hi all, both anntenae at 90 degrees to each other, but not on the same plane. No pun intended.  FB3

[Don Fry]

On 10/03/2023 at 12:07, Simon Chaddock said:

My own view is that it really does pay to keep the aerial(s) as far away as possible from other wires or even the battery.

I have a suspicion that what works flawlessly even at a test range can cause problems as the signal becomes weak. Modern 2.4 receivers 'recover' much better than they used to. Some of my early 2.4 took 3 seconds. An awful lot can happen in that time. 😲

 

This was not such a problem with the long aerials of 35 meg. It never ceases to amaze me how it still performs with the aerial just dangling out the back.   

I used to know a bloke, 35 meg days, long term flyer, very competent, who always faced his aircraft, and he waved his body about as if he imagined he was in the cockpit. With the aerial kept pointing at gyrating model. And lost signals came along time after time every flight. He just automatically flicked the aerial away from the model, and carried on as though it hadn’t happened. 

[Phil Green]

...

Edited March 13, 2023 by Phil Green

[Rich Griff]

May I ask, a single aerial Rx, how would you orientate that please.

 

Straight down vertically ?

 

Straight down to exit the fuz bottom and then bent 90 degrees to the rear ?

 

As above but at 45 degrees to the rear ?

 

Thanks.

[Nigel R]

Don't bend it,

 

and,

 

longitudinally.

[fly boy3]

Re my post above regarding arials at 90 degrees to each but not on same plane should have had a question mark with it, asI was hoping for a reply. My apologies.  FB3

[Don Fry]

90° to each other. Whether they are up down, across, or 45° inclined is not important. But avoid putting in on , say the battery, where the battery will act as a shield for the signal from many directions.

[fly boy3]

Thanks Don.  

[GrumpyGnome]

If possible, I try and avoid batteries, servos, servo leads, switches etc, etc. i.e. isolate them as much as I can. 

 

Definitely keep them well away from ignition units and HT cables in petrol models.....

[John Wagg]

Where practical I push the bare aerial ends through little holes to the outside. (at an angle to each other.)

Concerning the shielded part of the wires, are they not coaxial sheathed like TV aerial cable.?

 

[Andy Stephenson]

They are indeed coaxial cables like a much smaller version of a TV antenna cable.

 

The unshielded part is simply the outer stripped back to expose inner "active" element, however since this does not constitute a proper 1/4 wave antenna without a sleeve or a ground-plane*, the shielded part of the cable will have an effect on its performance and sharp bends which result in an increase in inductance in the first 30mm or so should be avoided to achieve maximum signal gain.

*Some receivers have this type of antenna.

[Richard Wills 2]

I have always made sure that the unshielded active part plus an equal length of the shielded part are kept in a straight line, and at 90deg to each other.

[Andy Stephenson]

They are indeed coaxial cables like a much smaller version of a TV antenna cable.

 

The unshielded part is simply the outer stripped back to expose inner "active" element, however since this does not constitute a proper 1/4 wave antenna without a sleeve* or a ground-plane, the shielded part of the cable will have an effect on its performance and sharp bends which result in an increase in inductance in the first 30mm or so should be avoided to achieve maximum signal gain.

*Some receivers have this type of antenna.

 

 

Edited March 16, 2023 by Andy Stephenson
Edited to make correction.

[Engine Doctor]

 

On 09/03/2023 at 14:54, Tosh McCaber said:

 

My question- is it important to just have the last uncovered wire at right angles to each other, or should the whole aerial cables be at right angles?

Yes . The rest of the lead can be in any orientation but I try to keep them as smooth as possible and not screwed up usually in plastic tubes fixed to the fuz interior

[Engine Doctor]

On 13/03/2023 at 22:34, Rich Griff said:

May I ask, a single aerial Rx, how would you orientate that please.

 

Straight down vertically ?

 

Straight down to exit the fuz bottom and then bent 90 degrees to the rear ?

 

As above but at 45 degrees to the rear ?

 

Thanks.

Ive used them ( FrSky) in any orientation. Just try to keep it away from any metal bits that can shield the signal, like batteries servos etc.