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-   -   Spektrum & JR 2.4 Folding antennas (http://www.Wattflyer.com/forums/showthread.php?t=73511)

Wildflyer 04-07-2014 06:05 AM

Spektrum & JR 2.4 Folding antennas
 
If you fly with a Spektrum or JR 2.4 radio's with the folding antennas, please be careful with the hinge. If the hinge breaks, it would be a good idea to get the antenna replaced as soon as feasible.

My antenna hinge broke, apparently one of the short hinge pins fell out. Just why they made this way is beyond me, it could have been so much stronger, so simply, it doesn't make sense.

I was trying to be gentle with the antenna until I could fix it. On the last time I took it out, I bumped the top of the antenna a little more than I meant to and it folded around backward, I put it back it the regular position and launched.

Just after the first turn the motor shut down (AR500 Rx) and the plane went in from about 300'. Busted up but repairable.

After I got home, I was looking at the broken hinge joint in the antenna, and noticed the coax antenna wire was pinched flat, clearly shorting the inner and outer conductors together.

Luckily my LHS had a replacement antenna, so I am back in business.

kyleservicetech 04-07-2014 05:45 PM

Quote:

Originally Posted by Wildflyer (Post 944743)
If you fly with a Spektrum or JR 2.4 radio's with the folding antennas, please be careful with the hinge. If the hinge breaks, it would be a good idea to get the antenna replaced as soon as feasible.

My antenna hinge broke, apparently one of the short hinge pins fell out. Just why they made this way is beyond me, it could have been so much stronger, so simply, it doesn't make sense.

I was trying to be gentle with the antenna until I could fix it. On the last time I took it out, I bumped the top of the antenna a little more than I meant to and it folded around backward, I put it back it the regular position and launched.

Just after the first turn the motor shut down (AR500 Rx) and the plane went in from about 300'. Busted up but repairable.

After I got home, I was looking at the broken hinge joint in the antenna, and noticed the coax antenna wire was pinched flat, clearly shorting the inner and outer conductors together.

Luckily my LHS had a replacement antenna, so I am back in business.


Good information, thanks.

FYI, I stopped using the antenna of my DX8 (And DX7's for that matter) for a carrying handle a long time ago. :oops: :eek: :cool:

JetPlaneFlyer 04-07-2014 05:58 PM

I never have heard a sensible reason why they put movable hinges on these antenna. The hinge only adds two things, both bad:
  • The possibility to orientate antenna 'straight out' .
  • A physical weak point.

Seems that Spektrum at least have finally cottoned on and are putting fixed antenna on all their new models. Most other manufacturers still use hinges.

xmech2k 04-07-2014 07:18 PM

Quote:

Originally Posted by JetPlaneFlyer (Post 944783)
I never have heard a sensible reason why they put movable hinges on these antenna. The hinge only adds two things, both bad:
  • The possibility to orientate antenna 'straight out' .
  • A physical weak point.

Seems that Spektrum at least have finally cottoned on and are putting fixed antenna on all their new models. Most other manufacturers still use hinges.

I don't think it's as simple as you make it sound. I'm pretty sure they were hinged because it was only one antennae, so you could orient it properly while still being able to fit in a normal box/case. Now they have 2 antennae, so one should always be oriented properly (sideways) towards the the model. At least that's how I understand it.

JetPlaneFlyer 04-07-2014 08:19 PM

Quote:

Originally Posted by xmech2k (Post 944786)
I don't think it's as simple as you make it sound. I'm pretty sure they were hinged because it was only one antennae, so you could orient it properly while still being able to fit in a normal box/case.

It seems simple to me i have to admit.

Why not have the antenna permanently 'bent' at 90 degrees, or better, a single antenna in that orientation built into the Tx case? Why should an aerial with a hinge give better RF performance that one without the hinge which was fixed in the optimal position?

I honestly cant think of a single reason why you would ever want to have the aerial pointed straight out, so why give the option to do so? But many newbies knowing no different fly exactly that way, risking loss of signal.

rcers 04-07-2014 08:33 PM

1 Attachment(s)
This is exactly why I am so happy with the new round of fixed mast antennas on many of the new transmitters on the market. You know that is there largely for show as we adjusted for several years to short antennas.

Placing them inside the case near the top is good enough for 2.4GHz. No great reason for the antenna mast at all. In fact my brand new Futaba 10j has none. There are actually 3 TX antennas two in the top and one in the handle. More than enough - an no breakage.

Mike

Turner 04-07-2014 09:17 PM

Quote:

Originally Posted by JetPlaneFlyer (Post 944789)
...Why should an aerial with a hinge give better RF performance that one without the hinge which was fixed in the optimal position?...

It wouldn't, of course, but it would probably be more difficult to store and case. They simply thought it was a reasonable alternative. If they had had their thinking caps on they would have devised the dual diversity antenna they offer today.

kyleservicetech 04-08-2014 12:15 AM

Quote:

Originally Posted by JetPlaneFlyer (Post 944789)
It seems simple to me i have to admit.

Why not have the antenna permanently 'bent' at 90 degrees, or better, a single antenna in that orientation built into the Tx case? Why should an aerial with a hinge give better RF performance that one without the hinge which was fixed in the optimal position?

I honestly cant think of a single reason why you would ever want to have the aerial pointed straight out, so why give the option to do so? But many newbies knowing no different fly exactly that way, risking loss of signal.

I did some testing on the transmitter antenna orientation awhile back. Pointing the antenna at your receiver does cut the range by perhaps one half, depending on radio mfg and a lot of other stuff.

So, now instead of two or three miles radio range, you've got 1 1/2 miles range. :D

I'd been flying my DX7's with the antenna straight out with no notable effect. For those that would like to beef up their transmitters antenna, take a run to Harbor Freight, pick up some appropriate diameter shrink tubing, and shrink it over the transmitters hinge.

Can't do it on mine, doing so, it won't fit into the carrying case.

Wildflyer 04-08-2014 05:00 AM

I have the same problem that many have, if my antenna doesn't fold, I can't use my case. I think I screwed up and left it out of it's case, and it slid into something. My set up is a 4'x8' roll-out carpeted floor in my truck, so I probably thought it was safe. I learned my lesson.

I generally have my antenna folded at a 45 degree angle, so it is pointed straight up.

I guess that would put it about a 45 degree to my plane,considering how I hold my Tx. Maybe in a perfect world, I would be better bending it at 90 degrees.
On the other hand I have seen people holding the Tx anywhere from pointing straight up slightly below their sight line, elbows bent almost as far as they go. Then a few people with their arms straight down and the Tx pointing at the ground.
These different ways to hold a Tx are probably why they are coming up with the new dual antenna systems.

You just can't think of everything the first time, the car industry is proof of that.

PS; Many people I have met do not understand that the wire at the bend point is a coax wire. (center conductor, inside a tube, inside a layer of foil wrapped with a woven shield of wire, then covered with a plastic outer jacket) they think it is just a wire. Only the last 31 mm (I believe) is a single wire. If the spacing between the center conductor and the shield conductor, is not correct, it will screw things up.

They actually make coax as small as sewing thread.

kyleservicetech 04-08-2014 05:26 AM

1 Attachment(s)
Quote:

Originally Posted by Wildflyer (Post 944843)

PS; Many people I have met do not understand that the wire at the bend point is a coax wire. (center conductor, inside a tube, inside a layer of foil wrapped with a woven shield of wire, then covered with a plastic outer jacket) they think it is just a wire. Only the last 31 mm (I believe) is a single wire. If the spacing between the center conductor and the shield conductor, is not correct, it will screw things up.

They actually make coax as small as sewing thread.

Yeah
What really surprised me was when doing that Spectrum Analyzer bit in another thread, how much difference was made in the radio frequency radiated signal strength when placing the transmitter on a wood bench, versus holding that same transmitter in your hands.

In either case, the full range is likely well over a mile, but how that transmitter was held made a difference.

If you look at Spektrums AR600-X receiver antenna, it is definitely a very small coax cable.

The attached photo (Taken with a Canon SX20IS Camera) shows the antenna's grey outer jacket, the insulated inner copper conductor, and right at the edge between the grey outer jacket and the insulation of the inner conductor, are some very fine copper mesh strands. That coax cable is much more obvious when viewed with my 20 power binocular microscope.

(I've had this unit for several years. Very nice. http://www.ebay.com/itm/Inspection-B...item2ea19a7049)

So, this coax antenna has a inside copper antenna lead, around that is the antenna lead semi-transparent insulation, around that is the copper mesh shield, and around the shield is the grey outer jacket.

Anyone that replaces one of these antenna wires with a piece of plain copper wire might really find that the radio range is for :censor:. :oops:

JenovaCell 07-15-2014 02:37 AM

I have a Futaba 10J for sale!
 
I'm selling a Brand New Futaba 10J if anyone is interested. Go to Craigslist and do a search for JenovaCell for more info. :)

solentlife 07-15-2014 07:51 AM

I always tend to smile at this antenna debate matter ...

I watch one guy with a tray and his Tx is only a few degrees up from horizontal. Another guy who uses a strap and his Tx is about 45 deg .... I use a strap and my Tx is often moving from 20 to 60 deg while flying.

The model is cavorting around the sky ... with it's antennae pointing in so many different directions during the flight.

How can anyone say which angle or direction an antenna should be ? We all basically look at model on ground, stand behind it ... and imagine link as that ... but that is only one orientation of the infinite number it goes through when it's flying.

For me ... I compromise, best way I can put it, with my Tx antenna canted to one side and angled about 45 deg up. My models - I lay antenna as best as possible, as clear of other parts as much as possible. I even like to drill small hole in fuselage and pass active tip out that hole and let it 'fly free' ...

So at end of day - the hinge on my antenna is used....

Interestingly ... my 9xr's have internal antenna already fitted but of course no module so far actually connects to it stock. The antenna lies at an angle up into the carrying handle ... and I believe it's a Dipole version similar to what FlySky use on their Rx's, except 9xr's doesn't have the red plastic sleeve.

Nigel

Turner 07-15-2014 02:12 PM

Quote:

Originally Posted by solentlife (Post 953107)
...How can anyone say which angle or direction an antenna should be?..

I hear you but it is a known fact that the transmitted signal is strongest off the side of the antenna and weakest straight off the tip. The Rx antenna picks up best on the side and least directly in line with the tip. Multiple Rx antenna when properly arranged increase reception reliability.

If the Z axis is the Tx antenna you want to keep the aircraft within the donut. With my Spektrum I point the antenna straight up while flying and don't fly directly overhead. This has proven reliable. I have forgotten to fold it on one occasion and lost control at about 400 ft distance at 50-60 ft up. The antenna was pointing directly at the plane. Reorienting the antenna restored control.

http://gallery.military.ir/albums/us...ed-512x384.png

solentlife 07-15-2014 03:58 PM

Quote:

Originally Posted by Turner (Post 953149)
I hear you but it is a known fact that the transmitted signal is strongest off the side of the antenna and weakest straight off the tip. The Rx antenna picks up best on the side and least directly in line with the tip. Multiple Rx antenna when properly arranged increase reception reliability.

If the Z axis is the Tx antenna you want to keep the aircraft within the donut. With my Spektrum I point the antenna straight up while flying and don't fly directly overhead. This has proven reliable. I have forgotten to fold it on one occasion and lost control at about 400 ft distance at 50-60 ft up. The antenna was pointing directly at the plane. Reorienting the antenna restored control.


I know I will regret this ... but if I had such happen - I would be seriously questioning my set-up ... 400ft is in my book not much more than range check distance at significantly reduced output ...

If I was 50- 60ft up and I lost control - I think I'd be hard pushed to move antenna in time to avoid the smash !

Anyway - we know about the orientation and best signal aspects ... but what I am saying is that models fly in 3 dimension and we also move while holding out Tx's ...

I sat for ages trying to come to a compromise angle / orientation for my Tx .. and best I could arrive at was 45 deg to left and 45 deg up.... basically if Tx is laid flat - my antenna was 45 deg from straight and pointing at 10:30 ... based on side propogation forward and up.
My models are both single antenna park 1000m and dual antenna 2km range jobs ... I orient them to be as best and clear as possible.

Nigel

Turner 07-15-2014 06:05 PM

Quote:

Originally Posted by solentlife (Post 953159)
I know I will regret this ... but if I had such happen - I would be seriously questioning my set-up ... 400ft is in my book not much more than range check distance at significantly reduced output ...

If I was 50- 60ft up and I lost control - I think I'd be hard pushed to move antenna in time to avoid the smash!..

You are not taking into account the particular environment I was flying in. Might easily been more than 400. It is just an estimate. My system was fine. Flew much greater distances before and after with antenna pointing straight up.

Losing control doesn't mean an instant crash. Was flying level on base leg at the time. Started to turn onto final and nothing. The plane continued on its course. I looked at my radio and realized the problem. Quickly turned the radio 90˚ and control was restored. Just in time as it was heading into a line of trees.

kyleservicetech 07-15-2014 07:06 PM

Quote:

Originally Posted by Turner (Post 953149)
I hear you but it is a known fact that the transmitted signal is strongest off the side of the antenna and weakest straight off the tip. The Rx antenna picks up best on the side and least directly in line with the tip. Multiple Rx antenna when properly arranged increase reception reliability.

If the Z axis is the Tx antenna you want to keep the aircraft within the donut. With my Spektrum I point the antenna straight up while flying and don't fly directly overhead. This has proven reliable. I have forgotten to fold it on one occasion and lost control at about 400 ft distance at 50-60 ft up. The antenna was pointing directly at the plane. Reorienting the antenna restored control.

]

Yeah
I did some testing on the transmitter antenna orientation with a Spectrum Analyzer.
http://www.wattflyer.com/forums/showthread.php?t=72719

As expected, aiming your transmitter antenna at your model does cut range significantly. Depending on transmitter Mfg, from maybe 2 miles something on the order of a few thousand feet.

Again, depending on transmitter and receiver mfg.

Just ran this test again on my Spektrum DX8 transmitter. With my Spektrum Analyzer at 100 feet from the transmitter, the Analyzer measured -58 dB with the transmitter laying flat with its antenna vertical. And, the Analyzer measured -74dB with the transmitter laying flat with the antenna pointed directly at the Analyzer. So, I set up a distance where my Analyzer showed -55 dB with the transmitter antenna vertical, then aimed the transmitter antenna at the Analyzer and walked closer to the transmitter to get the same -55 dB. That resulted in going from 50 paces from the transmitter to 7 paces to match signal strengths. Just moving 10 degrees away from the direction the transmitter antenna was pointing made a very significant change, nearly matching when the transmitter antenna was vertical.

That is a 16 dB loss in signal strength. Can someone in wattflyer provide information on how much a 16 dB signal reduction affects signal range mathematically?

That would be good info for all of us!

solentlife 07-15-2014 07:06 PM

Quote:

Originally Posted by Turner (Post 953185)
You are not taking into account the particular environment I was flying in. Might easily been more than 400. It is just an estimate. My system was fine. Flew much greater distances before and after with antenna pointing straight up.

Losing control doesn't mean an instant crash. Was flying level on base leg at the time. Started to turn onto final and nothing. The plane continued on its course. I looked at my radio and realized the problem. Quickly turned the radio 90˚ and control was restored. Just in time as it was heading into a line of trees.

Fair enough ...

It's the stating heights / distances etc. that in fact are extremely hard to do ... and be accurate. Ask any ships officer about it ... he looks out the bridge window and asked to estimate distance ... very hard to do unless you have a reference item to gauge it against.

So I assume you must have had last command failsafe then and not the usual shut throttle on loss of signal ?

;)

Nigel

solentlife 07-15-2014 07:10 PM

Quote:

Originally Posted by kyleservicetech (Post 953191)
Yeah
I did some testing on the transmitter antenna orientation with a Spectrum Analyzer.
http://www.wattflyer.com/forums/showthread.php?t=72719

As expected, aiming your transmitter antenna at your model does cut range significantly. Depending on transmitter Mfg, from maybe 2 miles something like a half mile.

Again, depending on transmitter and receiver mfg.

Denny ... 1/2 mile is 2640ft ... not 400 !

AND most people do not fly more than 1/2 mile anyway from central spot. More than that and you have problems orientating the model ...

Lets be honest !!

Nigel

kyleservicetech 07-15-2014 07:44 PM

Quote:

Originally Posted by solentlife (Post 953193)
Denny ... 1/2 mile is 2640ft ... not 400 !

AND most people do not fly more than 1/2 mile anyway from central spot. More than that and you have problems orientating the model ...

Lets be honest !!

Nigel


Hi Nigel
Yeah, I changed it to a few thousand feet.

FYI, I've got a 65 inch wingspan model that I took up to 970 feet high last year with one of those "How High Is It?" gadgets. At that altitude, the orientation of that model was pure guesswork. And, I've got 20-20 vision. :D

For those worried, our field is many many miles from the nearest airport.

Turner 07-15-2014 08:12 PM

Quote:

Originally Posted by solentlife (Post 953192)
So I assume you must have had last command failsafe then and not the usual shut throttle on loss of signal?

The DX5e and AR500 I was using at the time only drives the throttle channel to preset failsafe, low throttle in my case. Other channels receive no commands with loss of signal. So, since I was descending at low throttle preparing to land the only thing noticed was that it was not responding to my stick inputs.


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