Antenna Position
 

Hi all,

There appears to be two schools of thought relating to antenna positioning: inside the fuz, and outside. Thinking about it, most of the 2x2's I have seen, including photos, the antenna is not evident and presumabley must be inside the fuz. I would appreciate more guidance on this subject from all. I am currently building an Osmose and want to get the plane set up correctly. I will be running a bell-crank with a CH carbon rod, which as I understand it presents it own issues with running the antenna parallel, incl the pull - pull rudder.

Thanks
Roly.
ps. have conducted a search on RCU, but did not return as much as I hoped, hence I am reviving the subject.

RE: Antenna Position
 

Hi Roly
The antenna can be inside the fuz, no problem at all.
About the MK bell-crank, I really recommend using the CH D.E.P.S., it is far lighter and very accurate, but you should put the servo on its side.

Isaac Najary

RE: Antenna Position
 

I hide mine in every aircraft.

just join a bunch of drinking straws together and feed the antenna tube down that.

I try to keep it away from anything wire/carbon or both.

RE: Antenna Position
 

Carbon fiber and steel rudder cables, being electrically conductive, will absorb some radio signal. The trick with the antenna is to have it not be close to anything conductive, and not parallel, so that any blanking that does occur will only be at an angle across the antenna, not along its full length. A little blanking now and then as the conductive element and antenna move relative to each other with flight position and attitude will not be a problem. You do definitely need a tube of some sort to keep the antenna from flopping around inside the fuselage, and it should be probably close to the top of the turtleback, which would keep it a safe distance from pushrods & cables. An angled path for the antenna to get from radio compartment to top of turtleback interior is also not a problem.

RE: Antenna Position
 

I think that a secure antenna installation is important to secure reliability in the long run. To accomplish this you must place it inside the plane. If you bend any type of wire enough times it will break. A wire on the outside is vulnerable to damage and is constantly oscillating in the slipstream. If only a few of its wire strands break, it will cause the same type of noise as vibrating metal to metal contact points. You will be unaware of the deterioration of your antenna because it happens inside the insulation. Most RC pilots never replace their receiver antennas and install it from plane to plane on the outside. An accident waiting to happen! I normally use the inner of a thin cell-phone type coax as antenna wire. When I assemble the plane, depending on its size, I glue the end of the antenna under the vertical fin and keep all the battery and servo leads to one side of the fuselage and route my antenna on the opposite side, securing it with glue and cable ties. On the receiver I leave a short "pig tail" that I solder to the antenna and cover with heat-shrink after I have secured the antenna and receiver. Remember the total length of your antenna must be the same as the original (99cm for JR equipment). Wires and rods running along side the antenna will have little effect on its performance as long as they are not near a resonant length, for 35MHz this is about 2 meters and about 41 inch for 72 MHz.

RE: Antenna Position
 

You may also want to place the antenna tube in the part of the airplane that most often is visible by you when flying. I fly with about 12 other pattern flyers and we all put the antenna tube in the bottom of the fuse. It's basically a standard for all of us. We all use pull pull for both the rudder and the elevator and most of us are still using wire rather than kevlar thread and reception issues don't generally occur.

Better yet, go to spread spectrum and forget about antenna issues.

RE: Antenna Position
 

Thanks to all for responding to this thread, much appreciated. I think the issue for me is that the guys who have taught me are adamant that the antenna must exit the fuz and therefore I am a little nervous. However, as I understand it, radio frequencies "penetrate" quite happily and providing you watch the pull pull etc this should not be an issue. Besides, even if the antenna was outside, depending on the attitude of the aircraft it may not be in line of sight with the TX. Reckon I will do a little reading up on radio waves. If I find something simple enough for me to understand, will post.

RE: Antenna Position
 

Afraid I am the old school not so flexable person on this issue Roli is refering to . I know that it looks great being inside the plane but have had first had experience in the past where it did not work on some planes . One of the aircraft belongs to a fellow Jomac ( Johannesburg Aircraft Club ) member , Francois Greber. He has a large ( I think 27%) extra 300S which crashed on flight 3 or 4 due to interference ( radio went into fail safe mode ) . Fortunately not too much damage - happened on the landing . He had the antenna nicely taped to the bottom of the plane ( outside ) . He had the plane repaired and prior to a flight showed me he had range problems - looking at antenna postion I pulled it off against his will made him buy an external whip antenna - problem solved . I am also building an Osmose and it will certainly have an external antenna

RE: Antenna Position
 

At risk of stating the obvious, you should range check any new installation. For years I've installed the antenna for my 72MHz receivers inside the fuselage on both sailplanes and pattern. Sailplanes are typically flown at greater distance than a pattern plane. That is until my latest project, a sailplane. On the ground it would not get the recommended range with the antenna either in or taped to the fuse. When I attached the antenna end to the vertical stab tip, the ground range was 60% greater than the recommendation. I don't know if the reduced range was due to the fuse finish or the C/F pushrods.

Allan

RE: Antenna Position
 

Hello rolyjr,

I have around 50 flights in my Osmose, with the antenna inside (with tube), and the MK bellcrank using the 3/16 CH carbon tube and steel cables on the rudder, all parallel, no problems or glitches at all, ever.

What ever you decide to go, my only advice is, do a good range check, if it does pass, nothing should go wrong.

The theory is fine but the practice proves also theory is not always accurate, I think I posted pictures where you can see that install.

CPLR and BPLR are using the same set up, I did not invented this set up, they did it first, and proved to be fine in all respects.

Good luck

RE: Antenna Position
 

I always put mine inside. Never had any issue..This is with Airtronics equipment though..

Chris

RE: Antenna Position
 

JNP I do not think that you friend's problem with interferance in his Extra had anything to do with the fact that the antenna was outside the plane. By installing a whip antenna, that is probably not resonant ,you probably desensitised the receiver, making it les sensitive to noise but also reducing its range. The noise generated by the ignition system were probably mostly in a horizontal plane and by changing the antenna to vertical you decreased the noise level.

If you have a portable transistor radio that covers the shortwave bands, you can utilize it as a noise detector. Tune it to a clear portion of the highest short wave frequency, some goes up to 22MHZ (13 meter band). The level of electrical noise decreases when you increase the frequency, so don't worry that your receiver is receiving below 35MHz; it will just be more sensitive to noise. By placing the antenna of this receiver next to your servos and then moving them you will be able to hear any electrical noise present. The same technique can be used to determent the noise level of a petrol engine's ignition system. Most petrol engine pilots would be shocked if they heard how much noise they generate! The fact of the matter is that any petrol engine plane will have less range with the same 35 or 50 MHZ equipment than a glow powered plane. The 50MHz equipment will be slightly better than the 35MHz equipment, but the best equipment to use with a petrol engine is 2.4 GHz equipment.

RE: Antenna Position
 

Hi Piet , thanks your message well noted - will keep it mind . thks juan