Brainiax

I'm building a GP Yak 54 and there is a tube in place for the receiver antenna to feed through. Thing is, there's no way for it to exit the air frame. Is it necessary for the antenna to be on the outside at some point for better reception? Thanks.

Rodney

Does it need to be outside? Not usually, only if the airframe is a conductor such as all metal, a carbon fiber body etc. For a normal model formed from balsa, plastic, fiber glass, film covering etc. no problem as these materials are transparent to RF so the antenna does not know it is enclosed in anything.

airbusdrvr

Rodney is correct.

BuschBarber

My Feedback: (2)

You really need to do a good Range Check, with and without the motor running, just to be sure, before you fly.

Are you on 72Mhz?
What Tx and Rx are you using?

LesUyeda

I usually poke a hole in the covering, bring a couple of inches of antenna out, and tie a not in it to keep if from vibrating out of the tube and bunching up next to the receiver.

Les

BuschBarber

My Feedback: (2)

I have had numerous planes where the antenna worked fine, inside the fuse. There are others where I had too many glitches and running the antenna out the bottom and attaching it to the tail with a rubber band, solved the problem. I have also run the antenna out behind the canopy and up to the vertical fin did the trick.

I had to deal with more RF noise related issues, with gasoline engines, than with glow engines.

Whatever works to stop the Twitch.

Keep the antenna away from long steel or carbon fiber pushrods, servos, switches, and electric motors.

Brainiax

Ok, thanks guy's. I'm using a 7-cap FM 72mhz radio and a 168DP PCM receiver. With the antenna inside the tube it should not be affected by the pull-pull cable, correct? I guess I can try to snatch the end of the antenna and pull it through a hole in the tail of the fuse but it's gonna be painful trying to snag it.

BuschBarber

My Feedback: (2)

It is different with each radio and each plane. I don't think anyone can predict whether or not you can leave the antenna inside the plane. If the Range Check is OK, then it should be safe to fly. If you get a glitch in the air, investigate.

Given the same plane, constructed the same way, you could have different results with different radios.

I am half way to going fully 2.4. I have had virtually No issues with my 2.4 systems in the same planes with the same Tx. I have a JR XP9303 with a Spektrum 2.4 module. I also have an XP9303 with a JR 72Mhz Synthesizer module.

freeair

if your worried about where should the antenna wire go , do what i did and buy a Quick UK base loaded rx antenna. these are great on low wing sports models including jetts. all you need to do is drill a small hole in the the top of fuselage behind the canopy and fit the antenna vertical , there is no difference in range between this unit and the normal stock antenna wire but the anvantage is the antenna is well clear of any interferance problems such as wires / rods etc etc .

Rodney

When you say there is no difference in range between the stock antenna and the shorter one, what do you base your statements on? As an EE who has done a lot of RF work etc. it is technically not possible to have as long a range with a shorter antenna. If you do some really true tests using calibrated equipment, I think you will find that you will lose at least half your range. Fortunately, most modern receivers are good enough (sensitivity and noise rejection) to still give you reasonable performance with this loss in range. Unfortunately, this loss of range can be quite a bit worse than just losing half of it if the new impedance matching is slightly off.

victorzamora

If your plane has an antenna tube, take some baby powder and dust your antenna with it. It should then slide fairly easily down the tube. If not, and you still want to drag your antenna down your fuse and out a hole in the tail, it's not that hard to do if you follow this:

choose the hole you want, tie a nut to a string, drop the nut down the hole, tie the string to the antenna, pull string

BuschBarber

My Feedback: (2)

I have also run the antenna out through the side of the fuse and through a tube just inside the leading edge of the wing.

As far as Base Loaded Antennas go, there are many pilots with years of experience flying $5000+ turbine powered model jets with Base Loaded Antennas.

If, however, you want to get rid of the antenna routing problem, forever, get a 2.4 system.

Edwin

My Feedback: (2)

brainiax, I use about .032 music wire (why do they call it that?) to pull the antenna thru the tube. Just use a touch of CA to glue the end of the antenna to the wire. Then pull it thru and yank the wire off the ant.
Edwin

Brainiax

No problem getting the antenna through the tube. My main concern is the RF reception but it looks like its not going to be a problem, at least according to the consensus here and others I've asked about it. As long as the antenna is fully extended that it. Thanks guy's!!

freeair

firstly as an EE you must know alot about BASE LOADING of Antennas, example; do you see high range walki takies with long antennas these days ? have you noticed short TX and RX antennas on the new 2.4 gig radio sets? even though 2.4 gig has inside model antenna rx units , the tx has to have some sort of antenna which is no longer than 8 inches total. AM and FM receivers do have long antenna wires that go inside the fuselage and exit out the rear by a few inches , communication from the TX to the RX with am / fm is only picked up from whatever antenna is VISABLE [ nothing inside the fuselage ] a good quality Base Loaded Antenna that is suited to say an FM radio reciever comes in at half the total length from receiver to antenna tip, the standard length of the JR receiver wire is 1000mm and the unit i have [ quick u.k. ] when fitted up is exactly 500mm , even though the total length is really 1000mm thanks to the real base loading . i have done range checks with TX antenna down and up and have found no difference whatsoever between the two antenna set ups, i have club members that are running these in Jets and they also have no concerns. maybe we need to hear from other forum members that use this type of rx antenna. then this case can close .

Rodney

Freeair, you seem to have forgotten about "Capture Area"; base loading-properly done- helps but still does not overcome the other losses. Check out Mr. RCCam's website for some good information where tests have been done using good calibrated equipment under actual conditions. We in the RC hobby are very fortunate to have some good receiver designs available that will tolerate the compromises we make on antennas. I am not saying that they don't work, just that when we make those compromises we are sacrificing range and it is greatly reduced over that normally available. It is a simple matter of energy, for every 3DB lost, you lose half the range and most of these very short antennas have 3 to 6 DB of loss.

freeair

as i mentioned i have done both tx antenna down and up range checks and an example of the tx antenna down range check proved a decrease of only 7 foot compared to the same brand rx [ JR 10 ch PCM ] with its original antenna wire. range checks with TX antenna up only showed a loss in range of approx 15 feet , i must say this was a long walk in the paddock and i doubt i would fly a model this far away when in the air , which by rights should give even more clear range . at our club we do have altitude restrictions of 500 feet max so with well over 2000 feet of range i think i might be right.