Need assistance on building a Video TX antenna

[airmcn_3]

I want to take on a project of building a high gain transmitter antenna for my 2.4 GHz video system. I want to build a flat antenna that can be incorporated into the winglet of the aircraft.

Can anybody direct me in the right direction on how to go about this process?

Thank you,

Chris

[Ron W3FJW]

That setup would be directional and would have a lot of dropout not to mention the coax loss between the Tx and antenna unless the Tx was located on the winglet also.. Only decent antenna on the plane would be a vertical antenna.

[Tomapowa]

I assume when you say flat, you mean a dipole vice a patch...? (patch styles are more directional)
A few links that should help...
http://www.wlan.freeuk.com/tech/antenna/test-dipoles.htm
http://piers.mit.edu/piersproceedings/download.php?file=cGllcnMyMDA4aGFuZ3pob3V8MUFQXzAx ODIucGRmfDA3MDkwMTAyMzU0NQ==
http://www.emo.org.tr/ekler/d188b044333b4c6_ek.pdf
http://www.agilentads.com/2_Document/polarization_diversity_dipole_antenna_Feb06_2008.p df

A few calculators that should help... (2.4Ghz = dipole total length of 2.34")
http://bfn.org/~bn589/antenna.html
http://cdxa.org/antenna_cal_diople.html

We use this similar model on our UAV...
http://www.procerusuav.com/Downloads/TechSheets/TechSheet_Dipole_Antenna.pdf

[airmcn_3]

I assume when you say flat, you mean a dipole vice a patch...? (path styles are more directional)
A few links that should help...
http://www.wlan.freeuk.com/tech/antenna/test-dipoles.htm
http://piers.mit.edu/piersproceedings/download.php?file=cGllcnMyMDA4aGFuZ3pob3V8MUFQXzAx ODIucGRmfDA3MDkwMTAyMzU0NQ==
http://www.emo.org.tr/ekler/d188b044333b4c6_ek.pdf
http://www.agilentads.com/2_Document/polarization_diversity_dipole_antenna_Feb06_2008.p df

A few calculators that should help... (2.4Ghz = dipole total length of 2.34")
http://bfn.org/~bn589/antenna.html
http://cdxa.org/antenna_cal_diople.html

We use this simlar model on our UAV...
http://www.procerusuav.com/Downloads/TechSheets/TechSheet_Dipole_Antenna.pdf


Thank you I will take a look.

Chris

[Ron W3FJW]

We use this similar model on our UAV...

And you have no signal loss off the ends of the antenna or are you using 2 of them in a diversity setup?
All things being equal the radiation pattern is a figure 8 pattern perpendicular to the dipole.

[Tomapowa]

And you have no signal loss off the ends of the antenna or are you using 2 of them in a diversity setup?
All things being equal the radiation pattern is a figure 8 pattern perpendicular to the dipole.

A dipole in a vertical orientation is pretty much nondirectional irt the horizon... this is the way you get distance (horizontally) using a dipole. Maximum antenna radiation comes from the dipole in the direction which is perpendicular to the antenna's axis. With our video link we wanted to get maximum distance/range (UAV distance is usually greater than the altitude, especially for uUAVs).

http://en.wikipedia.org/wiki/Omnidirectional
http://en.wikipedia.org/wiki/Dipole_antenna#Ideal_half-wavelength_dipole
http://www.tpub.com/content/neets/14182/css/14182_186.htm
http://www.dxzone.com/cgi-bin/dir/jump.cgi?ID=11038

http://www.tpub.com/content/neets/14182/img/14182_186_1.jpg

[Ron W3FJW]

Ok. the dipole looked like it was horizontal in the first pic & the second one just looked like something you were playing with on the workbench. After a closer look, I can see it was just a set up to take pictures. What's the CB? An RF amp?

[Tomapowa]

Ok. the dipole looked like it was horizontal in the first pic & the second one just looked like something you were playing with on the workbench. After a closer look, I can see it was just a set up to take pictures. What's the CB? An RF amp?

The second pic you are referencing (http://www.rcgroups.com/forums/attachment.php?attachmentid=2339396) shows the dipole mounted (i.e. taped) vertically on the winglet (you can see the tip of one of the dipoles extending above the top of the winglet... with a red pc. of plastic insulation over it so we don't poke ourselves accidently. The circuitboard you referenced is manufactured by ProcerusUAV.com and I think their intention was to include some passive components to help tune/impedance-match the antenna... but after testing/tuning, they figured the passive components did not help much so they removed them, leaving it a true/blue dipole. The PCB also helps attach the dipole wires (crimped onto connectors of the PCB) and the antenna wire.

[rich smith]

Xbee docs indicate no advantage to dipole over simple whip at 2.4ghz. My own experiments found this to be true assuming the monopole has a groundplane at least an inch or so.

Coupled with RCCAMs $1 patch I don't think can be improved upon w/o going to extremes. I'd like to find out how to couple 4 of these patches into 24db super antenna.

I want to take on a project of building a high gain transmitter antenna for my 2.4 GHz video system. I want to build a flat antenna that can be incorporated into the winglet of the aircraft.

Can anybody direct me in the right direction on how to go about this process?

Thank you,

Chris

[airmcn_3]

Coupled with RCCAMs $1 patch I don't think can be improved upon w/o going to extremes. I'd like to find out how to couple 4 of these patches into 24db super antenna.


Sounds interesting, I am thinking about just simply putting my video TX in one winglet and my autopilot modem in the other, I can run the rubber antennas out the top/backside of the winglet at a slight angle.

I would be interested in hearing more on the coupling of these patch antennas.

Thanks,

Chris

[rich smith]

If you find out practical info I'd appreciate if you let me know. I understand theory of balun matching and actually opened a 24db from Super Circuits but foolishly sent it on to a client before documenting it.


Sounds interesting, I am thinking about just simply putting my video TX in one winglet and my autopilot modem in the other, I can run the rubber antennas out the top/backside of the winglet at a slight angle.

I would be interested in hearing more on the coupling of these patch antennas.

Thanks,

Chris

[Tomapowa]

Typically as you increase gain, you decrease beamwidth... typical of patch and helical antennas. These type of antennas are typically used for fixed point-to-point comms... and not too practical for moving objects such as UAVs since you need a method to constantly aim the antenna beam to the airborne transmitter/antenna. Your not talking about putting a patch style antenna on the UAV itself are you? If anything use a dipole/whip antenna on the aircraft and a patch/helix on the ground station receiver/transceiver.

I've built this helix but was not practical for our UAV ground station project:
http://www.wireless.org.au/~jhecker/helix/

[rich smith]

High gain antennas do not have to be narrow beam. Depends on how you deform or position director element. Or pointing each of the elements in the 4 antenna array off axis would allow customizing the radiation pattern.

Patch is not only practical but absolutely best solution for ground. Impractical for plane which needs omni.


Typically as you increase gain, you decrease beamwidth... typical of patch and helical antennas. These type of antennas are typically used for fixed point-to-point comms... and not too practical for moving objects such as UAVs since you need a method to constantly aim the antenna beam to the airborne transmitter/antenna. Your not talking about putting a patch style antenna on the UAV itself are you? If anything use a dipole/whip antenna on the aircraft and a patch/helix on the ground station receiver/transceiver.

I've built this helix but was not practical for our UAV ground station project:
http://www.wireless.org.au/~jhecker/helix/

[Tomapowa]

High gain antennas do not have to be narrow beam. Depends on how you deform or position director element. Or pointing each of the elements in the 4 antenna array off axis would allow customizing the radiation pattern.
If you are going to deform the elements to obtain a wider beam, you are defeating the whole purpose/design of the patch, and usually in turn reduce overall gain. Patch antennas by nature are directional and are most useful when it is desired to have the operational area in one general direction as opposed to all directions (omni-directional). It is designed to radiate and/or receive RF in one general direction, increasing the antenna's effectiveness in that direction. The beam width is much wider compared with a directional Yagi antenna's beam width, therefore precise antenna aiming and device positioning isn't necessary. Most patch style antennas have a 3dB beamwidth of around 60 degrees (http://en.wikipedia.org/wiki/Patch_antenna). In the case of a flying aircraft, unless you are always flying in one spot in the sky, you will have to move the patch to obtain optimal RSSI (Received Signal Strength Indicator).

Patch is not only practical but absolutely best solution for ground. Impractical for plane which needs omni.
Best solution depends on how much $$$ you have... best solution is a high gain yagi or helical style antenna which is automatically oriented to aircraft position in real-time (using the aircraft's GPS location). Other than that, for simplicity, a simple ground dipole should do.

Some interesting reading...
http://diydrones.ning.com/forum/topics/705844:Topic:46641
http://www.articlesbase.com/communication-articles/conformal-near-omnidirectional-antenna-design-for-unmanned-aerial-vehicles-uav-718325.html
http://video.aol.com/video-detail/qut-sruav-tracking-antenna/761564830
http://www.youtube.com/watch?v=FCHgS-0TUsE&eurl=http://www.rcgroups.com/forums/showthread.php?t=943365&page=2

[Tomapowa]

...I'd like to find out how to couple 4 of these patches into 24db super antenna...

Here's an idea...
http://www.ursi.org/Proceedings/ProcGA02/papers/p1835.pdf

[airmcn_3]

If you are going to deform the elements to obtain a wider beam, you are defeating the whole purpose/design of the patch, and usually in turn reduce overall gain. Patch antennas by nature are directional and are most useful when it is desired to have the operational area in one general direction as opposed to all directions (omni-directional). It is designed to radiate and/or receive RF in one general direction, increasing the antenna's effectiveness in that direction. The beam width is much wider compared with a directional Yagi antenna's beam width, therefore precise antenna aiming and device positioning isn't necessary. Most patch style antennas have a 3dB beamwidth of around 60 degrees (http://en.wikipedia.org/wiki/Patch_antenna). In the case of a flying aircraft, unless you are always flying in one spot in the sky, you will have to move the patch to obtain optimal RSSI (Received Signal Strength Indicator).


Best solution depends on how much $$$ you have... best solution is a high gain yagi or helical style antenna which is automatically oriented to aircraft position in real-time (using the aircraft's GPS location). Other than that, for simplicity, a simple ground dipole should do.

Some interesting reading...
http://diydrones.ning.com/forum/topics/705844:Topic:46641
http://www.articlesbase.com/communication-articles/conformal-near-omnidirectional-antenna-design-for-unmanned-aerial-vehicles-uav-718325.html
http://video.aol.com/video-detail/qut-sruav-tracking-antenna/761564830
http://www.youtube.com/watch?v=FCHgS-0TUsE&eurl=http://www.rcgroups.com/forums/showthread.php?t=943365&page=2


They did a really good job on this.

[rich smith]

Tomapowa, you're a little confusing on directionality of patches:

not too practical for moving objects such as UAVs since you need a method to constantly aim the antenna beam

beam width is much wider compared with a directional Yagi antenna's beam width, therefore precise antenna aiming and device positioning isn't necessary

Too much or too little? I need the "mama bear" solution and 4x patch is it.

Gain is gain and beamwidth is beamwidth, they are not the same and can be distributed as you please. It doesn't have to be Yagi style pencil beam nor omnidirectional mono. For UAVs high gain with in between directionality.

Best solution depends on how much $$$ you have... best solution is a high gain yagi or helical

I have exactly $4. In other words 4 of MR RCCAMs Goof Proof Patches. Actually let's allow another buck for balun or matching stubs.

I am well versed in RF and microwave theory. My needs are specific: practical knowledge on coupling patches. I want to buid a $200 Super Circuits antenna for $5. I played with this model and know it's exactly what's needed for my application. No interest in yagi or helix, and as far as tracking systems, been there-done that. If you are ever able to obtain info on coupling I will be eternally grateful.

BTW thanks for those links and the PDF. I have a feeling these will come in handy for other projects.

[Tomapowa]

Gain is gain and beamwidth is beamwidth, they are not the same and can be distributed as you please.....
I am well versed in RF and microwave theory ...

Huh? Sounds like you need to read this...
http://www.aticourses.com/antennas_tutorial.htm

An excerpt:
"The gain may be expressed directly in terms of the half power beamwidth by eliminating the factor D/l . Thus,

G = h (p k / a )2

Inserting the typical values h = 0.55 and k = 70° , one obtains

G = 27,000/ (a° )2

where a° is expressed in degrees. This is a well known engineering approximation for the gain (expressed as a numeric). It shows directly how the size of the beam automatically determines the gain. Although this relation was derived specifically for a reflector antenna with a circular beam, similar relations can be obtained for other antenna types and beam shapes. The value of the numerator will be somewhat different in each case."

Granted, there are other ways to increase gain but gain and beam are certainly related!

Rich,
Which Super Circuits patch antenna do you keep referencing?... The only non-amplified high-gain (20+dB) versions I thought they sell are the parabolic/dish or yagi versions...

[rich smith]

You are of course entitled to believe whatever you like regarding power vs pattern. I base my ideas more on personal experience and controlled measurements and less on books, internet, and theory. Although no stranger to those either.

The Super Circuits antenna was $200-$300 and 20 something db. Not sure they still carry it but had 4 small patches inside and worked better than anything for tracking my UAV. Bought several for a security system client and kicking myself now for not paying more attention to the interface.



Huh? Sounds like you need to read this...
http://www.aticourses.com/antennas_tutorial.htm

An excerpt:
"The gain may be expressed directly in terms of the half power beamwidth by eliminating the factor D/l . Thus,

G = h (p k / a )2

Inserting the typical values h = 0.55 and k = 70° , one obtains

G = 27,000/ (a° )2

where a° is expressed in degrees. This is a well known engineering approximation for the gain (expressed as a numeric). It shows directly how the size of the beam automatically determines the gain. Although this relation was derived specifically for a reflector antenna with a circular beam, similar relations can be obtained for other antenna types and beam shapes. The value of the numerator will be somewhat different in each case."

Granted, there are other ways to increase gain but gain and beam are certainly related!

Rich,
Which Super Circuits patch antenna do you keep referencing?... The only non-amplified high-gain (20+dB) versions I thought they sell are the parabolic/dish or yagi versions...

[Tomapowa]

You are of course entitled to believe whatever you like regarding power vs pattern. I base my ideas more on personal experience and controlled measurements and less on books, internet, and theory. Although no stranger to those either.
Unless your tests are tainted due to improper setup, etc... your results should be indicative of that based on fundamental antenna theory. My comments are based on my own personal knowledge & experiences, and often I have to direct some to published theory/facts to get certain points across, hence the internet links I provide.

The Super Circuits antenna was $200-$300 and 20 something db. Not sure they still carry it but had 4 small patches inside and worked better than anything for tracking my UAV. Bought several for a security system client and kicking myself now for not paying more attention to the interface.
I been purchasing from them for a while now and can't remember them ever selling a thing, especially a 20+ dB model. Seeing you purchased these in the past, do you have a model#? Stacking (i.e. cylindrical form) patch antennas together is not going to increase the overall gain. All it will do is allow you to get better coverage (omni-like) but with the same gain of an individual element/patch (you might get slight gain when patch beams ,typically 60 degrees, overlap). Here's an expensive ($600+) patch array setup.. and this only has a gain of 14dB: (their 20dB model is almost $2,000!)
http://www.l-com.com/item.aspx?id=20611

[rich smith]

Tomapowa, I'm glad we both have lots of personal experience now but you are lucky to live in a universe where theory prevails. I've tried many times to immigrate to lala land but rejected due to scientific bent. :) One of the first things I learned about RF design is it don't always behave according to theory specially at high frequency. Apparently you've been more fortunate.

Our disgreement, now and few weeks back, stems not from lack of theoretical knowledge but more from failure to understand my comments. I'll try again: power is generally fixed for a give aperture but can be distributed as you see fit. Directional or omni or in between. For example a wide pattern at low field density or narrow beam at higher density can be achieved for the same size antenns depending on type and shape. Simple physics.

I found that patch lowest in cost and easiest to build (only 2 components) so settled on it over other designs. You are implying they cannot be coupled which conflicts with what I've seen in commercial products. What did you find inside your antenna?


Unless your tests are tainted due to improper setup, etc... your results should be indicative of that based on fundamental antenna theory.

[Tomapowa]

HI Rich,
You really need to read this...
http://www.microwaves101.com/encyclopedia/Navy%20handbook/3.1%20Antennas.pdf

Sorry but I'm still a little confused on your comments... you state the obvious (narrowed beam=increased directivity) but what does this have to do with gain? When you say "power" do you mean gain? As you change aperature, beamwidth obviously changes thus affecting gain... isn't it really that basic? If not then I guess the Navy needs to update the books I was taught with (such as the one above in the link). That's why you will notice that most narrow beam (i.e. yagi/helical) antennas they sell have higher gain than that of dipoles and patches. You don't get something (high gain) for nothing... (especially for antennas of the same size/space requirement)

I never implied that patch antennas could not be "ganged". I've designed microstrip antennas in the past and have also messed with microstrip array antennas typically used for missiles. It's not a straight forward design process but it can be done if diligent. Patch arrays are readily available and are extensively used by communication co's for 360 degree coverage. The link I provided in the previously post shows you one ... but costs a few thousand. Can you show me a cheaper ($200 or so) patch antenna array with adequate gain without amplification? I've never seen one, hence I never purchased one to tear apart and reverse-engineer.

I think I make my point clear by providing substatianting info/links... and we can continue to disagree with each other... that's ok.

The main subject of this post was which type of antenna the poster could use on his airborne aircraft, not the ground station. By now he should know that the proper config is a dipole mounted vertically. As for the ground station antenna, I say use what ever you want that works to your satisfaction. But as with most serious UAV projects I've worked, your UAV is not always in front of you, thus a fixed position patch is not the proper solution.

[rich smith]

Thanks again for the links, I read it and learned a few things but nothing that would help with practical construction of current goal. May prove useful in the future for other projects.

Only Super Circuits lead ATM is flyer from the floor of our car. Lists $129 18db patch (ANT-PVX-18DB) which sound similar but not exactly what I recall. It must have some advantage over 6db RCCAM design but obviously not amplified like a similar looking $699 unit on same page (ANT-24-26). Didn't see any that cost thousands but this is an old flyer. Don't have current catalog or abilty to browse the site. Size of both appear to be exactly 4x RCCAMs one so maybe it is mine.

In any case I'm looking for easy to build solution to extend 2.4ghz range w/reasonable pattern and that was it.


HI Rich,
You really need to read this...
http://www.microwaves101.com/encyclopedia/Navy%20handbook/3.1%20Antennas.pdf

Sorry but I'm still a little confused on your comments... you state the obvious (narrowed beam=increased directivity) but what does this have to do with gain? When you say "power" do you mean gain? As you change aperature, beamwidth obviously changes thus affecting gain... isn't it really that basic? If not then I guess the Navy needs to update the books I was taught with (such as the one above in the link). That's why you will notice that most narrow beam (i.e. yagi/helical) antennas they sell have higher gain than that of dipoles and patches. You don't get something (high gain) for nothing... (especially for antennas of the same size/space requirement)

I never implied that patch antennas could not be "ganged". I've designed microstrip antennas in the past and have also messed with microstrip array antennas typically used for missiles. It's not a straight forward design process but it can be done if diligent. Patch arrays are readily available and are extensively used by communication co's for 360 degree coverage. The link I provided in the previously post shows you one ... but costs a few thousand. Can you show me a cheaper ($200 or so) patch antenna array with adequate gain without amplification? I've never seen one, hence I never purchased one to tear apart and reverse-engineer.

I think I make my point clear by providing substatianting info/links... and we can continue to disagree with each other... that's ok.

The main subject of this post was which type of antenna the poster could use on his airborne aircraft, not the ground station. By now he should know that the proper config is a dipole mounted vertically. As for the ground station antenna, I say use what ever you want that works to your satisfaction. But as with most serious UAV projects I've worked, your UAV is not always in front of you, thus a fixed position patch is not the proper solution.

[Tomapowa]

Rich,
So I understand you correctly, are you looking to design/purchase a single plane multi-patch antenna (where all patches are on same plane) or an antenna that has 4 patch antennas in a 360 degree pattern? (like this (http://www.l-com.com/product_images/detail/lg_HK2420-090NF.JPG)) I'm trying to visualize what you are looking for... the ones you mentioned (Supercircuits) appear single plane (multi patch or not)... Are you looking for better gain or better coverage?

[rich smith]

Actually something in between. As you mentioned a Yagi is too tight and certainly not 360. 4 on a pole, adjustable depending on mood, maybe.

For long distance all aligned, for local loitering spread out. Most of the time slightly off center generally pointed toward the plane. Or where I think it might be.

As far as purchase, if you find one for $5 shipped I'm all in! :)

Cost and ease of constuction overriding factors.

Rich,
So I understand you correctly, are you looking to design/purchase a single plane multi-patch antenna (where all patches are on same plane) or an antenna that has 4 patch antennas in a 360 degree pattern? (like this (http://www.l-com.com/product_images/detail/lg_HK2420-090NF.JPG)) I'm trying to visualize what you are looking for... the ones you mentioned (Supercircuits) appear single plane (multi patch or not)... Are you looking for better gain or better coverage?

[mjsas]

The Tx antenna is only half the system, the gain of the Rx antenna is just as important. You might consider putting all the effort into the Rx antenna and just use a mono pole or even a simple piece of wire antenna for the Tx.

[Tomapowa]

The Tx antenna is only half the system, the gain of the Rx antenna is just as important. You might consider putting all the effort into the Rx antenna and just use a mono pole or even a simple piece of wire antenna for the Tx.
That's sort of the discussion we have been having here... recommending a simple omni-directional dipole for the RF transmitter (since UAV always moving with varying attitude) and higher gain ground station antenna for the receiver (ground station).

The ground station's antenna "style" depends on a few factors such as distance between tranceivers/antenna, frequency, obstructions, bandwidth, etc... Hobbiest style UAVs tend to be smaller and usually are close in proximity (iaw FAA and AMA, these should be flown under 400' and have visual/control at all times) so a patch style high gain antenna should work great (3dB beam is around 60-70 degrees for most patches). As long as your model/transceiver is within that beam, you should have adequate reception. With larger/commercial UAV, these tend to be flown beyond visual/manual control (i.e. greater distances and locations) so a higher-gain antenna (helical or yagi) would be required... but since they have narrower beams, they will need to be positioned towards the vicinity of the UAV/transceiver as it moves about.

BTW, they do sell single plane patch antennas with much wider beams than 50-60 degress (actually, some are supposedly 360 degree!) but of course, with much lower gains.
http://www.superpass.com/MIMO-24.html

Rich, If I (or any one at that) determined how to build a $5 antenna with $200-300 worth of performance... do you really think the design/fabrication would get posted here? :eek: If anything, I'd start my own antenna business! :)