View Poll Results: How do you orientate your transmitter's antenna?
Pointing right/ left (horizontally)
69
33.17%
Pointing vertically up
86
41.35%
Pointing downwards to ground in front of you
32
15.38%
Pointing horizontally away from you
11
5.29%
Don't care (however it came out of the case)
10
4.81%
Voters: 208. You may not vote on this poll
Transmitter antenna orientation
#26
The most important part of how to position your antennas is in the plane. If the Rxer and Txer antennas are cross-polarized, there is a 30 db signal loss. This is about a 95%+ loss of signal. You need to ensure the Txer and the Rxers antenna have a similar polarization (i.e. if the Rxer is vertically polarized, then the most effective polarization for the transmitter is vertical.) Also, vertical is better than horizontal as the ground tends to absorb horizontal signals. How do you achieve constant vertical polarization? Point the Txer's antenna straight up and the three Rxers in the fuse with each of their antennas polarized differently. That way you have at least one antenna vertically polarized at all times. In jets and Giants, this is important as we fly them way out there. In parkflyers this is not nearly as critical.
That being said, not much signal is lost at 45 degrees off from vertical. But point the antenna directly at the plane and you are presenting the Rxer's with worst possible case. By the way, I think the DX18 and for sure the DX9 has two antennas. One vertical and there is a horizontal one in the carrying handle.
Use Flight log data to determine your transmitter's coverage area. You start seeing frame losses and you know you are getting close to the limit. Use real-time telemetry with an alarm on frame losses and your planes will never fly away from you.
That being said, not much signal is lost at 45 degrees off from vertical. But point the antenna directly at the plane and you are presenting the Rxer's with worst possible case. By the way, I think the DX18 and for sure the DX9 has two antennas. One vertical and there is a horizontal one in the carrying handle.
Use Flight log data to determine your transmitter's coverage area. You start seeing frame losses and you know you are getting close to the limit. Use real-time telemetry with an alarm on frame losses and your planes will never fly away from you.
#27
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I just started using the telemetry with the DX18 and its great, with it you get live feedback of how your radio system is performing, best place to spend $56 if you ask me
#28
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I have flown Spektrum, 2 DX6, 2 DX7, and one DX 7s and only had one instance that I could trace directly to the system in all those years. Never gave any thought to antenna orientation till I got telemetry that showed me real time rssi strength. Perhaps I had been flying on the ragged edge sometimes but never lost a plane. BTW, most of my flying for the last 30 years has been with Futaba, even when I had a few Spektrum.
Whoops, lightning explained it while I were typing...
Last edited by A10FLYR; 04-21-2014 at 06:13 PM. Reason: lightning strike...
#29
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Haha, I'm happy to see your on the same page, and you beat me to getting telemetry so its only fair I get to beat you to posting about it
Last edited by lightningmcnulty; 04-21-2014 at 11:34 PM.
#30
My Feedback: (2)
Having two antennas on a transmitter makes no sense. Hooking antennas together in parallel creates a composite, screwed up radiation pattern with nulls and lobes.
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
#31
My Feedback: (2)
Having two antennas on a transmitter makes no sense. Hooking antennas together in parallel creates a composite, screwed up radiation pattern with nulls and lobes.
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
JPM,
I will make guess that the RF signal alternates between the two Tx antennas.
It is my experience that all whip antennas have a null when pointed directly at the receiver or directly away from the receiver. I used to test my range by collapsing the Tx antenna , pointing the antenna directly at the model and fly out till I got a glitch. Then I would point the antenna vertical to recover control and if necessary quickly extend the Tx antenna. On my Royal Classic radio on 72mhz the model would be be farther out than I would normally fly when I lost control.
I am currently flying Weatronic and Taranis and as A10 says it sure is comforting the have the RSSI warning via telemetry which both my radios have.
#32
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I take in consideration the doughnut shaped radiation pattern of the antenna, but even so I prefer to keep it horizontally,avoiding the twisting and bending I may inevitably do to it before and after each flight. Inside the antenna case there is a thin cable that if break by fatigue will inevitably crash your plane.
Doing this since day one.. and not a problem whatsover in 5 years of flying 2.44 Ghz, even in crowded RF enviroments.
Doing this since day one.. and not a problem whatsover in 5 years of flying 2.44 Ghz, even in crowded RF enviroments.
#33
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Also no part of me believes that many/any lockouts are caused by TX antenna orientation, I believe that most "lockouts" are caused by, in this order
1 the pilot lying to everybody to cover his/her mistake, this is by far the biggest one, its a great excuse for those who can't admit their mistakes.
2 poorly maintained equipment (so many people use crashed equipment without proper inspection, spill fluid on rx's etc)
3 poorly installed equipment (bad wiring, general mistakes with connections/selection of supporting equipment)
4 poorly positioned equipment in the airplane
5 cheap equipment, its important to remember that its not impossible for that cheap steering servo you installed to cost you your plane!
this is just what I have observed, I have defiantly seen equipment failures and almost unavoidable accidents but I do think that most crashes can be accounted for by one of the above, also I know that everyone here who flys at a busy field all know that its the same people week in week out who experience "lockouts"
1 the pilot lying to everybody to cover his/her mistake, this is by far the biggest one, its a great excuse for those who can't admit their mistakes.
2 poorly maintained equipment (so many people use crashed equipment without proper inspection, spill fluid on rx's etc)
3 poorly installed equipment (bad wiring, general mistakes with connections/selection of supporting equipment)
4 poorly positioned equipment in the airplane
5 cheap equipment, its important to remember that its not impossible for that cheap steering servo you installed to cost you your plane!
this is just what I have observed, I have defiantly seen equipment failures and almost unavoidable accidents but I do think that most crashes can be accounted for by one of the above, also I know that everyone here who flys at a busy field all know that its the same people week in week out who experience "lockouts"
However, one day my DX8 alarmed on telemetry data and I noticed that I had a frame loss (far less of a problem than a hold). At that point I noticed that I was holding my transmitter pointed toward the ground (as someone else in the thread mentioned that we need to avoid doing) and even though the antenna was properly positioned, the angle I was holding my transmitter left the antenna tip pointing towards my aircraft. I thought that was interesting and tried a little test. I flew my plane a little higher - to give me plenty of recovery time - and purposefully pointed my antenna tip towards the plane and then away. I found that the only way I could induce a frame loss was by pointing the antenna tip toward the plane. It definitely makes a difference.
Paul
Last edited by SkidMan; 04-22-2014 at 07:43 AM.
#34
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A suggestion for improving the poll.
More and more transmitters are coming out with rigid dual diversity transmitter antennas. You might consider adding a "I use a transmitter with fixed dual diversity antennas."
More and more transmitters are coming out with rigid dual diversity transmitter antennas. You might consider adding a "I use a transmitter with fixed dual diversity antennas."
#35
Having two antennas on a transmitter makes no sense. Hooking antennas together in parallel creates a composite, screwed up radiation pattern with nulls and lobes.
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
Multiple antennas work on an airplane because there are mutliple receivers and a computer to decide which antenna to listen to at any particular time based on which is providing the better signal.
In order to use two transmit antennas to advantage the transmitter would need to transmit two separate signals (codes) with the airborne receivers/computer deciding which one to use. I don't think our radio systems do this.
Maybe the second antenna on the transmitter is the telemetry receive antenna?
#36
My Feedback: (2)
Yes, in order to produce circular polarization you need the antennas co-located and fed with equal signal levels offset in phase by 90 electrical degrees. That it is not the case we are discussing.
We are talking about two spatially separated antennas with a relative phase that is uncontrolled.
Sidgates may be right on with his thought of alternating between the two antennas. I think that would work. When the signal from one atnenna becomes too weak the airborne system would still receive every other frame.
We are talking about two spatially separated antennas with a relative phase that is uncontrolled.
Sidgates may be right on with his thought of alternating between the two antennas. I think that would work. When the signal from one atnenna becomes too weak the airborne system would still receive every other frame.
Last edited by JPMacG; 04-22-2014 at 12:51 PM.
#37
How do you know the two antennas are not properly phased and not positioned optimally, given the ergonomics of a typical transmitter? I am pretty sure Andy has told us the straight scoop and with my 45+ years of RF experience, I believe him. If you can show me proof of your statements, I'll consider believing you. In the meantime. I'll stick with Horizon's explanations of how their products work.
By the way, some of your other statement about how the receivers work together are also incorrect. I talked the Rxer processing out with Andy a long time ago. When using multiple Rxers, they all are listening simultaneously and each Rxer's data is processed. First one with the right checksum is executed. And, ... why would you need a third antenna for telemetry when you already have two that are perfectly set up for the given RF wavelength? All you need is a little time displacement multiplexing with priority and the antennas can work for both datastreams.
You might want to search around a bit. All this info is on this site. Just trying to help you a bit here.
By the way, some of your other statement about how the receivers work together are also incorrect. I talked the Rxer processing out with Andy a long time ago. When using multiple Rxers, they all are listening simultaneously and each Rxer's data is processed. First one with the right checksum is executed. And, ... why would you need a third antenna for telemetry when you already have two that are perfectly set up for the given RF wavelength? All you need is a little time displacement multiplexing with priority and the antennas can work for both datastreams.
You might want to search around a bit. All this info is on this site. Just trying to help you a bit here.
#38
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Len,
I am sorry if I have angered you. Please don't take my postings as a personal attack. That was certainly not my intent.
In order to produce a circularly polarized radiation pattern over a wide beamwidth the two linear antennas would need to lie in the same plane within a tenth of an inch or so. If the two antennas are offset more then they could still produce CP, but their CP axial ratio would fall off rapidly as one moved off axis, quickly deteriorating back to linear. This is because of the change in path length from the rx antenna to each of the linear tx components.
I design antennas for a living so I have seen quite a bit in my 36 years of antenna design. But I have been wrong before, so I apologize if I am. Can you please provide a link to Andy's statement saying they are circularly polarized?
And yes, you are right, I have been sloppy with my terminology in my previous posts. I talked of signals becoming weak, but the true indicator of a good signal is the checksum. Checksum errors tend to occur on the weaker signal, but there no doubt are exceptions.
I don't know why the designers might use a separate antenna for telemetry rather than multiplexing the main antenna. Perhaps to reduce cost? Or to reduce insertion loss? Or to improve reliability? It was just a guess.
Anyway, I am drifting way off topic. I suggest we continue this discussion by PM if you care to.
73,
w2anz
I am sorry if I have angered you. Please don't take my postings as a personal attack. That was certainly not my intent.
In order to produce a circularly polarized radiation pattern over a wide beamwidth the two linear antennas would need to lie in the same plane within a tenth of an inch or so. If the two antennas are offset more then they could still produce CP, but their CP axial ratio would fall off rapidly as one moved off axis, quickly deteriorating back to linear. This is because of the change in path length from the rx antenna to each of the linear tx components.
I design antennas for a living so I have seen quite a bit in my 36 years of antenna design. But I have been wrong before, so I apologize if I am. Can you please provide a link to Andy's statement saying they are circularly polarized?
And yes, you are right, I have been sloppy with my terminology in my previous posts. I talked of signals becoming weak, but the true indicator of a good signal is the checksum. Checksum errors tend to occur on the weaker signal, but there no doubt are exceptions.
I don't know why the designers might use a separate antenna for telemetry rather than multiplexing the main antenna. Perhaps to reduce cost? Or to reduce insertion loss? Or to improve reliability? It was just a guess.
Anyway, I am drifting way off topic. I suggest we continue this discussion by PM if you care to.
73,
w2anz
#39
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I have no idea why the DX18 has 2 antennas but I did read that they both are used for regular purposes and to provide diversity. I have no idea what this means but i'm willing to bet my jets that spektrum have some idea of what they are doing in this arena.
I suggest that comments like this are backed up with hard technical data before you get everyone who flys with an 18 worried about their systems
I suggest that comments like this are backed up with hard technical data before you get everyone who flys with an 18 worried about their systems
#40
I have no idea why the DX18 has 2 antennas but I did read that they both are used for regular purposes and to provide diversity. I have no idea what this means but i'm willing to bet my jets that spektrum have some idea of what they are doing in this arena.
I suggest that comments like this are backed up with hard technical data before you get everyone who flys with an 18 worried about their systems
I suggest that comments like this are backed up with hard technical data before you get everyone who flys with an 18 worried about their systems
Last edited by Justflying1; 04-22-2014 at 08:28 PM.
#41
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Point the antenna sraight at Your head. That way if You lose signal due to pointing antenna straight at the model, its best to put the TX on the ground and pull out the umbrella like the coyote does just before the big rock lands on Him. LOL Seriously, point the antenna at Your head!
#45
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I think the orientation of the antenna is not a big issues as transmitter and receiver are not fixed and moreover the antennas are the Omni directional antennas and radiate equally in all directions so the receiver will capture the signal as far as it is the coverage area of transmitter.
#46
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I think the orientation of the antenna is not a big issues as transmitter and receiver are not fixed and moreover the antennas are the Omni directional antennas and radiate equally in all directions so the receiver will capture the signal as far as it is the coverage area of transmitter.
#47
Cross polarized antennas lose ~30 db of the available signal. That equates to an ~ 98% signal loss. While a vertical antenna may be omni-directional, a horizontal antenna is not. You may want to read up a bit on RF propagation. It may just save you a plane or two and a lot of $s. And, ... all it takes is a little reading.
#48
Thread Starter
I think the orientation of the antenna is not a big issues as transmitter and receiver are not fixed and moreover the antennas are the Omni directional antennas and radiate equally in all directions so the receiver will capture the signal as far as it is the coverage area of transmitter.