Go Back  RCU Forums > RC Airplanes > RC Jets
Reload this Page >

Transmitter antenna orientation

Notices
RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems
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

Old 04-21-2014, 04:21 PM
  #26  
Len Todd
 
Join Date: Jul 2012
Location: Baldwin, MI
Posts: 1,626
Likes: 0
Received 38 Likes on 34 Posts
Default

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.
Old 04-21-2014, 06:10 PM
  #27  
lightningmcnulty
My Feedback: (11)
 
Join Date: Sep 2010
Location: marina del rey, CA
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Steve Collins
OK. So if you buy into the notion that antenna pointing direction is important, how do you rationalize a transmitter, such as the Spektrum DX18, which has a rigid antenna?
The DX18 has two antennas, one is the obvious one and the other is in the handle so clearly they think polarization is important.

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
Old 04-21-2014, 06:12 PM
  #28  
A10FLYR
My Feedback: (1)
 
A10FLYR's Avatar
 
Join Date: Dec 2001
Location: Littleton, CO,
Posts: 1,639
Received 0 Likes on 0 Posts
Default

Originally Posted by Steve Collins
OK. So if you buy into the notion that antenna pointing direction is important, how do you rationalize a transmitter, such as the Spektrum DX18, which has a rigid antenna?
I don't rationalize Spektrum's rigid antenna but I do know what my rf system likes because it tells me. Antenna orientation has always been a problem. Many a plane have been lost when antenna was pointed directly a plane some distance away when landing. We still hold the radio above our heads with the antenna straight up when trying to regain control of an airplane going down out of control.

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...
Old 04-21-2014, 11:32 PM
  #29  
lightningmcnulty
My Feedback: (11)
 
Join Date: Sep 2010
Location: marina del rey, CA
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Default

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.
Old 04-22-2014, 05:42 AM
  #30  
JPMacG
My Feedback: (2)
 
Join Date: Jan 2002
Location: Ivyland, PA
Posts: 2,299
Received 1 Like on 1 Post
Default

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?
Old 04-22-2014, 06:26 AM
  #31  
sidgates
My Feedback: (2)
 
Join Date: May 2002
Location: Denver, CO
Posts: 1,425
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by JPMacG
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?
-------------------------------------------------

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.
Old 04-22-2014, 07:21 AM
  #32  
erbroens
 
erbroens's Avatar
 
Join Date: Nov 2003
Location: Curitiba, Parana, BRAZIL
Posts: 4,289
Likes: 0
Received 14 Likes on 11 Posts
Default

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.
Old 04-22-2014, 07:34 AM
  #33  
SkidMan
My Feedback: (17)
 
Join Date: Apr 2010
Location: Oviedo, FL
Posts: 349
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by lightningmcnulty
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"
I like your list. Just add poorly designed, maintained, and installed electric systems - Such as 1100 mAh 4-cell NiMh receiver packs on planes with numerous servos, high power servos, or both.

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.
Old 04-22-2014, 07:38 AM
  #34  
SkidMan
My Feedback: (17)
 
Join Date: Apr 2010
Location: Oviedo, FL
Posts: 349
Likes: 0
Received 0 Likes on 0 Posts
Default

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."
Old 04-22-2014, 12:21 PM
  #35  
Len Todd
 
Join Date: Jul 2012
Location: Baldwin, MI
Posts: 1,626
Likes: 0
Received 38 Likes on 34 Posts
Default

Originally Posted by JPMacG
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?
Actually, .. you are wrong. A horizontal and a vertical antenna phased together makes a circular polarized array. Which greatly helps overcome cross-polarization. Now, ... if the two antennas were not phased properly, then you may experience some degradation. But if they are phased properly then your statement is incorrect!
Old 04-22-2014, 12:41 PM
  #36  
JPMacG
My Feedback: (2)
 
Join Date: Jan 2002
Location: Ivyland, PA
Posts: 2,299
Received 1 Like on 1 Post
Default

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.

Last edited by JPMacG; 04-22-2014 at 12:51 PM.
Old 04-22-2014, 01:07 PM
  #37  
Len Todd
 
Join Date: Jul 2012
Location: Baldwin, MI
Posts: 1,626
Likes: 0
Received 38 Likes on 34 Posts
Default

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.
Old 04-22-2014, 02:55 PM
  #38  
JPMacG
My Feedback: (2)
 
Join Date: Jan 2002
Location: Ivyland, PA
Posts: 2,299
Received 1 Like on 1 Post
Default

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
Old 04-22-2014, 07:17 PM
  #39  
lightningmcnulty
My Feedback: (11)
 
Join Date: Sep 2010
Location: marina del rey, CA
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Default

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
Old 04-22-2014, 08:25 PM
  #40  
Justflying1
 
Join Date: Apr 2011
Location: Melbourne, AUSTRALIA
Posts: 860
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by lightningmcnulty
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
+1 I don't have an idea also but I can tell you I have thrust in my DX18 and JR 11 X no matter what anyone else say. I set than up according to there recommendations as they are the experts, I do all the appropriate checks, and never had a problem.

Last edited by Justflying1; 04-22-2014 at 08:28 PM.
Old 04-23-2014, 02:40 AM
  #41  
Hinckley Bill
My Feedback: (569)
 
Join Date: Jun 2002
Location: Illinos
Posts: 898
Likes: 0
Received 9 Likes on 8 Posts
Default

Originally Posted by F-16 viperman
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!
Just about spewed out my first morning cup of coffee on reading this.........where's the ACME MFG Company when you need it eh?
Old 04-24-2014, 08:18 AM
  #42  
Jeti USA
Senior Member
 
Join Date: Jun 2013
Location: , FL
Posts: 423
Likes: 0
Received 0 Likes on 0 Posts
Default

I guess I do not care, I have 4x fully integrated antennas and 2x Independent RF modules.
All angles are covered on my Jeti DS-16

Zb

Old 04-24-2014, 09:37 AM
  #43  
lightningmcnulty
My Feedback: (11)
 
Join Date: Sep 2010
Location: marina del rey, CA
Posts: 199
Likes: 0
Received 0 Likes on 0 Posts
Default

I want one of these pretty bad, I just can't bring myself to make the jump from the 18
Old 04-24-2014, 10:50 AM
  #44  
Ron101
My Feedback: (22)
 
Ron101's Avatar
 
Join Date: Aug 2004
Location: Brentwood, CA
Posts: 1,833
Likes: 0
Received 3 Likes on 3 Posts
Default

Futaba shows either 90 degrees vertical or 90 degree horizontal with the tip of the antenna being the weakest...
so just don't point it at the plane

I do 90 degrees to the left horizontal and my telemetry system is mounted on my controller with it's antenna to the right
Attached Files
Old 06-05-2014, 10:12 AM
  #45  
civi
Junior Member
 
Join Date: Jun 2014
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Default

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.
Old 06-05-2014, 11:14 AM
  #46  
jetster81
Senior Member
 
Join Date: Feb 2011
Location: london, UNITED KINGDOM
Posts: 864
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by civi
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.
Quite a sweeping statement for a first post, let us know how you get on.
Old 06-05-2014, 07:52 PM
  #47  
Len Todd
 
Join Date: Jul 2012
Location: Baldwin, MI
Posts: 1,626
Likes: 0
Received 38 Likes on 34 Posts
Default

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.
Old 06-06-2014, 02:57 AM
  #48  
Craig B.
Thread Starter
 
Join Date: Dec 2002
Location: PERTH, AUSTRALIA
Posts: 1,413
Likes: 0
Received 5 Likes on 5 Posts
Default

Originally Posted by civi
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.
...yeah just a few glaring errors in that statement...
Old 06-06-2014, 03:41 AM
  #49  
gooseF22
 
gooseF22's Avatar
 
Join Date: Aug 2006
Location: Fort Wayne, IN
Posts: 2,603
Received 2 Likes on 2 Posts
Default

Lightning, go see David "LAjetguy", he can show you a couple first hand.. he lives in SoCal.. if you want to check out the Jeti Tx..
Old 06-06-2014, 07:00 AM
  #50  
szhsfghu
Junior Member
 
Join Date: Jun 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

guys, how do I add to/ edit the poll options?

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.