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Old Feb 21, 2012, 01:08 PM
The lunatic is on the grass
ridgewalker's Avatar
Joined Aug 2008
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Quote:
Originally Posted by markus123456 View Post
This is a so called pot antenna. It's a form of a dipole. The outer metal cylinder you refer to is one of the poles. Soldering the legs to it is a big no no. What you can to to gain some of the cable is unsoldering it and the solder the legs to the mesh that is below the cylinder.

HTH

Markus
Thank you Markus...secretspy711 and Eastcoast78...

Cylinder will be removed before soldering legs.

Before attempting,the length of the mesh shield from the connector to the top of the cylinder is 65mm,is that an acceptable length for the cloverleaf to be from the connector?

I did read....http://www.rcgroups.com/forums/showp...&postcount=936

So i'm guessing (would like some confirmation) that this cable should be long enough.

This will be a 5.8Ghz antenna.




Ridgewalker
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Old Feb 21, 2012, 01:31 PM
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Switzerland, LU, Buchrain
Joined Aug 2006
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Quote:
Originally Posted by ridgewalker View Post
Thank you Markus...secretspy711 and Eastcoast78...

Cylinder will be removed before soldering legs.

Before attempting,the length of the mesh shield from the connector to the top of the cylinder is 65mm,is that an acceptable length for the cloverleaf to be from the connector?

I did read....http://www.rcgroups.com/forums/showp...&postcount=936

So i'm guessing (would like some confirmation) that this cable should be long enough.

This will be a 5.8Ghz antenna.




Ridgewalker
6cm is safe. The wavelength is around 5.1cm which is the minimum not to be within the so called nearfield.

Markus
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Old Feb 21, 2012, 04:38 PM
Opt
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New Zealand, Auckland
Joined Oct 2010
414 Posts
I just did a quick test on my newly built cloverleaf measuring the 500 mw vtx current.
I built it for lawmate channel 8 (2510 mHz). Channel 8 drew about 40 mA more than channel 1. But so did the stock whip, and the CL drew exactly the same current as the stock whip... I guess I didnt build it quite right, but I will try it anyway and hope it is close enough!
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Old Feb 21, 2012, 05:52 PM
Nakelp
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United States, NJ, Union
Joined Sep 2004
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Cant find any link to cross hair antenna, help, help :-)
PLS
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Old Feb 21, 2012, 05:59 PM
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United States, VA, Madison Heights
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Go to FPVLab.com its on there not here.
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Old Feb 21, 2012, 06:07 PM
Nakelp
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United States, NJ, Union
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Thx, no wonder I cant find anything LOL
Thx again
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Old Feb 22, 2012, 06:34 PM
RTFM
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Antarctica
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My first 5.8ghz CL ... thx alex
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Old Feb 22, 2012, 10:32 PM
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Joined Dec 2011
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Markus or IBCrazy,
If I were to experiment with a thin film antenna of this CL design. What would be the best trace width, and would it differ for the different frequencies? And how 'sharp' a corner if I can print perfect right angles? I have some special 'fold away' requirements. I intend to keep the geometry intact.
Quote:
Originally Posted by markus123456 View Post
From looking at your pictures, I get the impression that this CL whilie not the most beautifull one I ever saw should work. What caught my atention though is how close the camera is to the antenna. From the size (hard to judge on a pciture only) it looks like your on 1280Mhz right?

You must know that CP antennas, especially when made with thicker wire and not so sharp bends are fairly wideband. So it could be that the antenna intercepts EMI that comes from the camera or more likely the other way round?

Just a thaught. You could try to find this out by takeing the components out of the plane and do ground tests with them much more seperated, eventually even by carfully packing the camera into aluminium foil.

Could you try to quantify what you expected and how it performed?

Markus
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Old Feb 23, 2012, 01:12 AM
multi rotors,foamies,car lover
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Quote:
Originally Posted by markus123456 View Post
It should be better in close range, eventually not reaching out the same (but not dramatically less). However, at that frequency (asuming you use a 500mW tx) you should get way more range with both antenna setups. So, eventually your area where you fly is very very polluted (high noise floor) or something else is not ok. CP antennas, especially helicals, pick up more signals from other frequencies than linear antennas, stuffing your receivers input stage thus lowering sensitivity by a great deal which could explain the phenomeon.

Now that I'm fully awake (tuff night behind me ) I don't think it's interference. How about flying your setup in a more rural area just to know if things are improved dramatically?

Markus
Dear Markus,
last summer i purchase from readymaderc theses antenna:http://www.readymaderc.com/store/ind...roducts_id=459

this antenna combined with fatshark and immersion rc 600mw was used for my quadcopter fpv . but since i have a crash i used my stock antenna 5.8ghz and i get better range around house and tree can you explain me why ? i don't say your 60$ antenna doesnt work but what happening if my signal decrease or out of range with the stock antenna and bluebeam ? blue screen ? thanks
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Old Feb 23, 2012, 02:13 AM
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Quote:
Originally Posted by windfou View Post
Dear Markus,
last summer i purchase from readymaderc theses antenna:http://www.readymaderc.com/store/ind...roducts_id=459

this antenna combined with fatshark and immersion rc 600mw was used for my quadcopter fpv . but since i have a crash i used my stock antenna 5.8ghz and i get better range around house and tree can you explain me why ? i don't say your 60$ antenna doesnt work but what happening if my signal decrease or out of range with the stock antenna and bluebeam ? blue screen ? thanks
Ok, these are not "my" $60 antennas I'm not Alex. I charge $20 per antenna. So much about that.

These antennas should be used with a coax extension cable. If you mount them as is, the nearby rx or tx will violate the near field of the antenna, changeing it's radiation pattern significantly.

Wether they work well or not also depends on many factors. As a matter of fact, CP antennas on 5.8G - provided the individual antenna is not defective and well built and tuned - outperform linear antennas easily. However, if an antenna is not well built, bent, defective or mistuned, performance might be very poor. Those antennas, based on the wire thickness are obviousely delicate and one must take care not to bend them. You should asume that antennas you get fullfil the other requirements (well built, no dents, tuned). If not, this is IMHO a waranty kind of situation. I can only speak for myself but I figure Alex and Hugo also take their work seriousely. If one of my customers gets a not well performing antenna, he will get a free replacement. If the plane crashes and the antenna gets dented (or get's dented while handling it) one can send me the antenna for repair at the cost of the return shipping fee provided the antenna is not totally smashed.

I suggest you contact either redymaderc or Alex about that.

Regarding the general performance of CP antennas over linear ones I can say that CP antennas have two significant advantages. Advantage number one is that they almost totally cancel out reflections. Reflections are very very common the higher the frequency is. In fact, frequencies around 5Ghz and up are often used for radar applications because they DO reflect so well. Every reflection of the signal that arrives at the receiver antenna will cause an interfrenence in the receiver leading to a disorted signal / picture. Advantage nuber two is that CP antennas almost do not depend on the positioning of the receiver and transmitter antennas compared to each other. Linear antennas HAVE to be alligned for best performance. If they are "crossed up" (in a 90 degrees angle to each other), you loose 12dB and in layman terms, that's more than 100 times less of the signal. Not so with CP antennas.

Other than this, linear antennas as well as CP antennas have to radiate (in case of the tx antenna) and receive the signal. Both do that equaly well. What I'm trying to say is that there are no "wonder antennas". There are antennas which are well adapted to a specific problem (like CP antennas for FPV where the plane banks and where we have reflections due to the frequencies used) and some which are not so well adapted (linear antennas are not good with banking and reflections). If we compare these antenna types, we must assume that such comparison is made with tuned antennas such that each antenna has a chance to truly radiate or receive. If this is not given (like it seems to be the case with the antennas you have) such a comparison is pointless.

Markus
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Old Feb 23, 2012, 02:26 AM
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Quote:
Originally Posted by readyman View Post
Markus or IBCrazy,
If I were to experiment with a thin film antenna of this CL design. What would be the best trace width, and would it differ for the different frequencies? And how 'sharp' a corner if I can print perfect right angles? I have some special 'fold away' requirements. I intend to keep the geometry intact.
Nice idea about the thin film. I belive half of the world is seeking a solution to mass produce such antennas at low costs. The problem I see with the thin film aproach is the drag such an antenna would create in the air and the obvious subsequent dynamic deformation.

Regarding your specific questions I can't tell you much as I'm lacking experiance with PCB based antennas. However, in general the thinner the wire (trace) the more narrowband the antenna will be, and the more important it becomes that it is well tuned.

If you want to take your developement seriousely, you IMHO have to invest into a vector network analyzer and go through numerous design / prototype cycles to find a good solution. Constantin A. Balanis book called "antenna theory" most likely contains information about PCB antennas along with probably any other aspect and theoretical information about antenna design.

HTH

Markus
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Old Feb 23, 2012, 07:18 AM
I need a bigger shed..
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Australia, TAS, Launceston
Joined Nov 2011
1,498 Posts
Got my bixler mostly setup I will be flying LOS with others watching/recording on the laptop until I have CP antennas
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Old Feb 23, 2012, 12:11 PM
multi rotors,foamies,car lover
windfou's Avatar
Joined Dec 2008
1,462 Posts
Quote:
Originally Posted by markus123456 View Post
Ok, these are not "my" $60 antennas I'm not Alex. I charge $20 per antenna. So much about that.

These antennas should be used with a coax extension cable. If you mount them as is, the nearby rx or tx will violate the near field of the antenna, changeing it's radiation pattern significantly.

Wether they work well or not also depends on many factors. As a matter of fact, CP antennas on 5.8G - provided the individual antenna is not defective and well built and tuned - outperform linear antennas easily. However, if an antenna is not well built, bent, defective or mistuned, performance might be very poor. Those antennas, based on the wire thickness are obviousely delicate and one must take care not to bend them. You should asume that antennas you get fullfil the other requirements (well built, no dents, tuned). If not, this is IMHO a waranty kind of situation. I can only speak for myself but I figure Alex and Hugo also take their work seriousely. If one of my customers gets a not well performing antenna, he will get a free replacement. If the plane crashes and the antenna gets dented (or get's dented while handling it) one can send me the antenna for repair at the cost of the return shipping fee provided the antenna is not totally smashed.

I suggest you contact either redymaderc or Alex about that.

Regarding the general performance of CP antennas over linear ones I can say that CP antennas have two significant advantages. Advantage number one is that they almost totally cancel out reflections. Reflections are very very common the higher the frequency is. In fact, frequencies around 5Ghz and up are often used for radar applications because they DO reflect so well. Every reflection of the signal that arrives at the receiver antenna will cause an interfrenence in the receiver leading to a disorted signal / picture. Advantage nuber two is that CP antennas almost do not depend on the positioning of the receiver and transmitter antennas compared to each other. Linear antennas HAVE to be alligned for best performance. If they are "crossed up" (in a 90 degrees angle to each other), you loose 12dB and in layman terms, that's more than 100 times less of the signal. Not so with CP antennas.

Other than this, linear antennas as well as CP antennas have to radiate (in case of the tx antenna) and receive the signal. Both do that equaly well. What I'm trying to say is that there are no "wonder antennas". There are antennas which are well adapted to a specific problem (like CP antennas for FPV where the plane banks and where we have reflections due to the frequencies used) and some which are not so well adapted (linear antennas are not good with banking and reflections). If we compare these antenna types, we must assume that such comparison is made with tuned antennas such that each antenna has a chance to truly radiate or receive. If this is not given (like it seems to be the case with the antennas you have) such a comparison is pointless.

Markus
ok so depend the side i turn the aicraft i can lose lot of signal with my linear stock antenna but the cp antenna the patern is diferent and you lose less signal and not need to turn my head to reach the siganl ok thanks i want a set from you please pm me
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Old Feb 23, 2012, 12:45 PM
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Thanks Marcus,
Has anyone experimented with 1/2 wave or 1/4 wave versions of the CL design? If a flyer just wants the omnidirectionality attributes but does not need to fly into the next country. This in order to scale down the physical size.
I've searched this thread but nothing comes up.

Quote:
Originally Posted by readyman View Post
Markus or IBCrazy,
If I were to experiment with a thin film antenna of this CL design. What would be the best trace width, and would it differ for the different frequencies? And how 'sharp' a corner if I can print perfect right angles? I have some special 'fold away' requirements. I intend to keep the geometry intact.
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Old Feb 23, 2012, 01:27 PM
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Switzerland, LU, Buchrain
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Quote:
Originally Posted by readyman View Post
Thanks Marcus,
Has anyone experimented with 1/2 wave or 1/4 wave versions of the CL design? If a flyer just wants the omnidirectionality attributes but does not need to fly into the next country. This in order to scale down the physical size.
I've searched this thread but nothing comes up.
That's not possible. If you make the lobes to be 1/2 or 1/4 of the wavelenght, you actually end up with double (1/2 size) or four times (1/4 size) of the resonant frequency.

Markus
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