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Discussion: Antenna position

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Discussion: Antenna position

Old 06-25-2020, 01:56 PM
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CARS II
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Default Discussion: Antenna position

Last week I flew my foamy model Bixler for the first time, during the maiden flight I experience a signal lost for about 5 seconds ( the ESC has a fail safe mode, motor to idle ) I was able to regain control by running to it ( it was very low and closed by ) also by lifting the radio above my head, all has been good since then ( some 20 flights by now ) the one thing I noticed and moved right after regaining control was the antenna possition, it was leaning towards me, I moved it forward to a 45 possition where I normally fly my airplanes, I concluded that the receiver was not getting a strong signal from the radio ( very low to the ground, antenna in a position for the weakest signal transmition )

This event has me thinking if I'm not taking advantage of the strongest antenna position available, I fly Futaba, I have an elbow on my antenna and fly with the antenna pointing forward on a 45 possition, I've seen others positioning the antenna on their radios to a horizontal possition, I wonder if I should be doing the same to get the best possible signal strength for my jets when I fly them.

Please post your opinions or suggestions.

I found this video, I can assure you, the author is not me ( I'm a more handsome guy ) but we both bear the same name, I've heard of him before via a vendor, I supposed he is somewhat known in the small aircraft community.

He got me when he mentioned that the wire inside the antenna body could break after so many times of been moved by rotating the anntena to the storage possition which is sideways.


Tks.

Last edited by CARS II; 06-25-2020 at 02:27 PM.
Old 06-25-2020, 05:36 PM
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jsnipes
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You never want the tip of the antenna pointed at your plane. So, the answer may be different for everyone, depending on their body position/movement while flying. E.g. if antenna is horizontal with the tip pointed to the left and you always stand perpendicular to the field with it, then when your plane is on the left side of the field the tip is pointing at it or could possibly point at it. But If you turn your body to each side as the plane flies by then the side of the antenna is always toward the plane. So it depends.

Tx’s with two antennas or four antennas in them do not suffer from this issue and eliminate this risk in most cases.

Rx antenna position in the plane is another topic altogether, though very critical as well.

My 0.02 ....

JS
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Old 06-25-2020, 05:58 PM
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From an RF perspective: Cross-polarized antennas reduce the signal strength ~ 96%. That is why one should have multiple Rxers in any plane one value. Use at least three Rxers/antenna systems with each antenna system oriented differently such that one Rxer's antenna is always polarized the same as the Txer. Also, if you have the Txer's antenna parallel to the electrical ground, you can kiss ~ 50% of that 4% goodbye. Do not allow any Rxer's antenna to be close to wiring or carbon materials. Do not allow Rxer antennas to be in parallel with wiring. Couple inches away and have the antennas at an angle to the wiring. Current quality TXers have at least two antennas with different orientations to help overcome cross-polarization, etc...

From an equipment perspective, some of the Futaba Rxers have a history of such failures. I do not recall the model #(s) and the nature of the issue. But there was a lot of discussion going on about that..
Old 06-25-2020, 06:42 PM
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Carlos,

Never point the antenna 45 up. You will have your plane in the cone of silence that radiates from the tip of your antenna. I have seen most Futaba users point their antenna 45 degrees DOWN or completely sideways
I personally feel this is a huge outage of Futaba. Spektrum and Jeti have two antennas at 90 from eachother, so you basically eliminate the cone of silence. Not sure if newer Futabas or JR have multiple antennas
Old 06-25-2020, 07:19 PM
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Thank you for all of your recommendations.

Jaime, I will have pay attention at how I stand when I fly my airplanes next time, I do know for a fact that some times I do a bit of a dance, I don't follow the airplane like some guys I've seen, I just swing back and forth

As far as set up, I do my best to keep any wires away from the receiver itself and specially the antennas, always fix them at 90 angle, so that is cover.

Jack, I hear what you are saying regarding the cone of silence. I'm looking at my future new radio and the 16chl Futaba is looking good to me, I will find out if it has two antennas.

Starting tomorrow I will be flying with the radio antenna sideways.

Thanks again guys.

Last edited by CARS II; 06-25-2020 at 07:24 PM.
Old 06-26-2020, 02:32 AM
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bodywerks
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Spektrum transmitters, the new ones at least, don't have a swivel antenna and don't have any problems. Why? Because the TX actually has two antennas in it at right angles to each other - one in the handle and one in the classic antenna location. with 2.4ghz, signal path diversity is key. I believe Jeti and Powerbox share this feature(dual tx antennas), whereas I believe Multiplex, JR, and Futaba still only have one.
I also don't fly futaba or any other radio without the ability to locate receiver antennas wherever I want them while also having the receiver module exactly where I want it at the same time(unless you also buy a $500+ powerbox system or equivelent and extra receivers).

Last edited by bodywerks; 06-26-2020 at 02:46 AM.
Old 06-26-2020, 03:27 AM
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This just happened to me. Check this out:

18 SZA Transmitter Antenna Orientation
Old 06-26-2020, 04:40 AM
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See post #2.

Glad that you did not lose your plane!

This is a link to a pretty good and relevant article. https://www.rchelicopterfun.com/rc-antenna.html

Key takeaways from article relative to this discussion ..


(I would have swapped the red and green to show the tip of the antenna as red, but you get the point.)

In short, our RF link will be:
  • Strongest when both the Radio & Receiver antennas are parallel to each other.
  • Weaker when they are perpendicular to each other.
  • Very weak when pointed ends on, directly at each other.

Originally Posted by MaJ. Woody View Post
This just happened to me. Check this out:

18 SZA Transmitter Antenna Orientation
Old 06-26-2020, 04:49 AM
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jsnipes
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My understanding is that Jeti DS-16 has 4 antennas (2 horizontal and 2 vertical) and Jeti DS-24 has 5 (2 horizontal, 2 vertical, plus the 900 MHz antenna).

From the Jeti website ...
  • Dual-Band 2.4GHz & 900MHz, triple redundant with five (5) integrated antennas.

Originally Posted by bodywerks View Post
Because the TX actually has two antennas in it at right angles to each other - one in the handle and one in the classic antenna location. with 2.4ghz, signal path diversity is key. I believe Jeti and Powerbox share this feature(dual tx antennas), whereas I believe Multiplex, JR, and Futaba still only have one.
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Old 06-26-2020, 06:59 AM
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CARS II
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Out of curiosity I crack open my radio to check on the antenna, looks good and here is how I secure the antennas on all my installs.


Last edited by CARS II; 06-26-2020 at 07:52 AM.
Old 06-26-2020, 09:28 AM
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Bob_B
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The antenna next to the tanks is a bad Idea
Old 06-26-2020, 11:08 AM
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CARS II
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Well guys, the very thing that I was trying to avoid just happened, on my second flight today I had a fail safe shutdown, I could hear the engine spooling down, then nothing....the Boomer was in an excellent position for a runway landing, it made it just fine to the runway.

I was flying with the antenna on a horizontal position for the first time ever and I got into the failsafe, flying with the antenna in the semi-vertical position has never given me any problems.

Never, ever before any of my receivers have gone into failsafe mode, I will be testing the radio with my foamy then with one of my small nitro gas airplanes, if I loose one of those, no biggie.

Last edited by CARS II; 06-26-2020 at 04:43 PM.
Old 06-26-2020, 11:17 AM
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Time to pack up and go home with a one piece airplane

Old 06-26-2020, 11:30 AM
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Originally Posted by Bob_B View Post
The antenna next to the tanks is a bad Idea
Why? I don't have any set up like that but I've heard not to install them alongside wiring, near a pump, not on carbon, keep them 90 degrees to each other, etc - not having one up against a plastic fuel tank never came up. Will a full tank block signal?
Old 06-26-2020, 12:37 PM
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Agreed with Auburn02, I have flown the Boomer easily over 20hrs with two different engines and never had a signal lost problem.
Old 06-26-2020, 12:38 PM
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CARS II
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Just completed 5 flights on my Bixler without a hitch, it may no be a jet but it flew without any problems.

Last edited by CARS II; 06-26-2020 at 02:25 PM.
Old 06-26-2020, 01:17 PM
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jsnipes
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Glad that you were able to get back to the field and have no damage! Was the jet on the same side of the field as the antenna was pointed to when your failsafe occurred?

Back when I had a Tx with just one antenna like that I always did it straight up (90 degrees bent, like you have in the photo with the Bixler) ... not 45 deg and not horizontal. My thinking was that with the tilt of the Tx as I was holding it, the antenna tip was pointed back over my head with it in the straight up position. So the tip could never be pointed at the plane.

I also tend to turn my body toward the jet when its on either side of the field. I’ve always been very conscious about where the antenna tip is pointed.

That was just my personal preference back then. I’m sure if you ask 10 people you’ll get 10 different answers.

Flying turbine jets made me re-think my equipment and setups ... way less worried about losing a jet than hurting someone or damaging property. Of course, I don’t want to lose a jet either! LOL! I’ve been flying turbines since 2003 and my equipment has evolved. The best way to not hurt anyone or property is to always have control of the jet. My goal is to put as much safety factor between the jet and the ground as possible, but also without an overly complicated setup. The Jeti DS-24 really checks all those marks for me from a triple redundancy standpoint, multiple antennas in Tx and jet, along with other reliability related features. I particularly like being able to log all of my receiver antenna data (antenna strength, and Q) and review after each flight. I can look for anything out of the ordinary in about 10 seconds and even overlay the data onto Google Earth to see if there is a pattern to any signal related anomalies if I want to.

I’m not starting a brand war here ... there are a number of perfectly capable systems out there. To each their own. I’m just saying that for me I have a Tx system that I use for foamies and the like and I have another system that I use for turbine jets and other high performance aircraft where maintaining control is at a premium priority.

JS

Originally Posted by CARS II View Post
Well guys, the very thing that I was trying to avoid just happened, on my second flight today I had a fail safe shutdown, I could hear the engine spooling down, then nothing....the Boomer was in an excellent position for a runway landing, it made just fine to the runway.

I was flying with the antenna on a horizontal position for the first time ever and I got into the failsafe, flying with the antenna in the semi-vertical position has never given me any problems.

Never, ever before any of my receivers has gone into failsafe mode, I will be testing the radio with my foamy then with one of my small nitro gas airplanes, if I loose one of those, no biggie.

Last edited by jsnipes; 06-26-2020 at 01:28 PM.
Old 06-26-2020, 02:36 PM
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JS

Yes it was, the airplane was at the 2 o'clock position high when it went into failsafe, the antenna pointing to the right.

I also use a 7clh Futaba for my simple and inexpensive models, the Jeti DS is one if the radios I'm considering as a replacement for my 10chl Futaba but I also like the 16SZA Futaba for my next radio and all my receivers will work with it.

Last edited by CARS II; 06-26-2020 at 04:37 PM.
Old 06-26-2020, 03:04 PM
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Antennas radiate on the sides. There are dead zones in the direcetion it points...like a donut hole. I flew with the antenna parallel to the runway with my previous radios. Jeti now.
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Old 06-26-2020, 05:22 PM
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Originally Posted by CARS II View Post
JS

Yes it was, the airplane was at the 2 o'clock position high when it went into failsafe, the antenna pointing to the right.

I also use a 7clh Futaba for my simple and inexpensive models, the Jeti DS is one if the radios I'm considering as a replacement for my 10chl Futaba but I also like the 16SZA Futaba for my next radio and all my receivers will work with it.
If you saw my thread in the Futaba support forum, you know that this exactly where my jet was when I got locked out and had a failsafe shutdown. I am going to be pointing my antenna bent in the down position. The way I hold the radio, this should give me a good radiating signal across the entire flight line. Bent over 90 degrees or tilted 45 degrees will leave my plane with no signal at the extreme edges of the runway left or right. Pointing down or straight up so that the tip is basically aimed at my forehead it's really the only way to go I guess.I'll be flying my giant scale Hellcat this weekend so I'm going to test an antenna position out on that but granted that thing doesn't get nearly as far away as the jet does.
Old 06-26-2020, 06:30 PM
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CARS II
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I did but will go over the entire thread tonight, yeah! I'm with you on the antenna position on Futaba radios.

Please keep me informed of your findings, I will also be flying my P47 tomorrow and will try the antenna pointing down and will report my results here.

Tks.

Last edited by CARS II; 06-26-2020 at 06:32 PM.
Old 06-26-2020, 06:55 PM
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According to Bill ( Futaba product support ) he also has experienced the right side low signal thing on the Futtaba equipment.

This is from that thread.
I'd say that is an improvement for sure. But the biggest thing is to NEVER point the TX antenna at the model. I've seen so many problems with the off the right side thing. Even bit me a few times. I like down towards the ground or straight up. Strongest signal is off the sides and that is what you want the model to "see".
Old 06-26-2020, 07:40 PM
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When I fly I usually have the radio this way.

Old 06-26-2020, 07:42 PM
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After reading some of the threads, I will start using the radio this way, since I can't point it donward on this radio.
Old 06-26-2020, 07:45 PM
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And this a no, no for this radio, belly not included

I'm also extending the strap down to have more room to move the hands over the radio to reach the switches.

Last edited by CARS II; 06-26-2020 at 07:48 PM.

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