16 replies to this topic

[Mr.RC-Cam]

The popular Goof Proof Patch is an easy-to-build antenna upgrade for your video Rx. Details can be found here: http://www.rc-cam.com/gp_patch.htm.

Note: For 1.2Ghz operation, multiply ALL dimensions by 2.0. For 900Mhz, multiply by 2.67. The two sheet metal elements should be 18-20 gauge to support the increased aerial size.

Yb2normal's implementation of the 2.4Ghz Groundplane antenna for the video Tx can be found here: http://www.yb2normal.com/antenna3.html.

S51KQ's 13cm (2.4Ghz) and 23cm (1.2Ghz) Double Quad antennas for the video Rx can be found here: http://lea.hamradio....1kq/ANTENNA.HTM

Cyber-Flyer's 2.4 GHz Turnstile (crossed dipoles) Tx antenna design is described here: Turnstile Antenna.

These antennas can be used together for a serious improvement in performance. At least as compared to the stock dipoles that are supplied with most wireless video systems.

An example of a home built antenna can be seen below (GP Patch):

Attached Thumbnails

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[mklarich]

I see all these patches and ground plane antennas and personally I have tried a number of antennas in different configurations. I have a number of small patchs from 5db up to a whooping 19db patch. I even got the 24db dish/grid antenna but the best antenna I have found so far is probably one of the simplest ones to find.

It is a 15.4 dbi omni-antenna, I got mine from fleeman-anderson-bird at
http://www.fab-corp.com/I1.htm
and it is the easiest antenna I have yet to use. We did some testing about a month ago with a 1 watt 2.4 tx in an ultralight and we were able to receive P5 signal from over 20 miles away with this antenna. The transmitter in the ultralight was using the dinky little stock 2db rubber duck antenna that comes stock with the TX.

I need to play around some more and see if there is a null over the top of the antenna but I am doubting there will be much of one. This antenna is about 70 inches from tip to connector and I have had it mounted to my truck going down the highway at 70 mph with no problem.

We had posted some info about this setup before but I just wanted to drop me 2 cents again with the new forum.

Matt Klarich
AUAV
KC9AXW

[KE4UVQ]

I just visited the FAB site and read up on the antenna you have, is no wonder
it works so well, its made by Comet, Ive been praising their dual and tri band
fixed station and mobile antennas for the ham bands for years.

I use a triband 144-222-444 CX-333 at home for VHF/UHF.

[mklarich]

Yep, I forgot to mention the part about it being a comet. I have seen the exact same antenna in AES (amatuer electronic supply) for about $20 more then FAB corp plus FAB has a bunch of other great 2.4 stuff.

Matt

[PeterB]

Hi there Mr RC-CAM,

I was unable to find any details of the theory or simulation S/W that you used to design the GPP Antenna. Would you be able to share with me/us what design tools or equations you used ?

I have encountered Ansoft Designer SV and other freeware simulation tools. What did you use ?

regards
Peter

The popular Goof Proof Patch is an easy-to-build antenna upgrade for your video Rx. Details can be found here: http://www.rc-cam.com/gp_patch.htm.

[Mr.RC-Cam]

I didn't use any simulation design tools. The basic information came from microwave RF books and some data found online. And then many hours of range testing with several different receivers.

[PeterB]

Can you recommend any particular books ? Did you keep any of your design notes that we might be able to reference ?

I'd like to repeat what you did for myself in order to better appreciate the method behind designing patch antennas.

regards
Peter

I didn't use any simulation design tools. The basic information came from microwave RF books and some data found online. And then many hours of range testing with several different receivers.

[Mr.RC-Cam]

The GP Patch project was published about seven years ago (~2002). So, gathering any design notes from that era is a bit troublesome. I recall that information on patch antenna design was very hard to come by. I would imagine that this has changed and more information and design tools are probably available to you. At this point Google would be your best resource.

[W3FJW-Ron]

Cyber-Flyer's 2.4 GHz Turnstile (crossed dipoles) Tx antenna design is described here: Turnstile Antenna.

Keeping in mind that a Turnstile is a horizontally polarized antenna and there may be some cross polarization loss with a vertical omni-directional antenna if used on the ground Rx as commonly supplied. ....

[PeterB]

OK, thanks.

The theory is out there but in text books. There is nothing substantial or in depth enough on websites. One online calculator allows you to simulate an edge fed patch but won't provide the calcs/theory to convert that to a probe fed patch as per the GPP. This paper comes close with an explanation about matching the impedance but no solid theory to follow through with.

As for freeware simulation S/W. I haven't yet downloaded any but these two look promising
Ansoft Designer SV and Sonnet

As for a source of definitive and comprehensive theory, thankfully now Google allows us to search the university level text books which we can purchase if we need to (book content preview is understandably limited and misses pages).

regards
Peter

The GP Patch project was published about seven years ago (~2002). So, gathering any design notes from that era is a bit troublesome. I recall that information on patch antenna design was very hard to come by. I would imagine that this has changed and more information and design tools are probably available to you. At this point Google would be your best resource.

[W3FJW-Ron]

Here's one paper on theory & design that can be scaled to 2.4gc. There are a lot more out there with some serious searching. VHF/UHF ARRL antenna handbooks should have something on patch antennas.

http://www.cst.com/C...ns/Ar...STUDIO®

Edited by W3FJW-Ron, 26 January 2009 - 05:53 PM.

[PeterB]

That article is a glorified advertisement for the CST MICROWAVE STUDIO product.

It presents little theory, no equations and nothing about matching the impedance to 50ohms by using a probe fed rather than the standard edge fed patch design that it presents.

Sorry to say but there is just NOT a lot out there for free !!

regards
Peter

Here's one paper on theory & design that can be scaled to 2.4gc. There are a lot more out there with some serious searching. VHF/UHF ARRL antenna handbooks should have something on patch antennas.

http://www.cst.com/C...ns/Ar...STUDIO®

[Mr.RC-Cam]

It presents little theory, no equations ...

Along with library visits, similar online published works were used in the GP Patch design efforts. I also bought several modern antenna books from arrl. No single publication had satisfying information, not even close. But collectively, the little bits and pieces, from dozens of sources, helped out.

I spent several weeks searching out the info I needed. Honestly, I am surprised that finding the information is still just as tough today. Especially considering that Internet search engines were a bit rusty back then. Had I known, I might have attempted to write a design guide. Too late for that!

Here's another online publication that might help fill in some blanks (or maybe not). The web is full of this stuff, just waiting to be sifted for gold:
http://www.orbanmicr...ch_Antennas.pdf

Sorry to say but there is just NOT a lot out there for free !!

Be careful, because you often get what you pay for.

[W3FJW-Ron]

It presents little theory, no equations and nothing about matching the impedance to 50ohms by using a probe fed rather than the standard edge fed patch design that it presents.

Sorry. I had no problem understanding it and getting out of it what was needed to move it to 2.4gc or any reasonable frequency.. I sometimes forget that some who post in this forum are not necessarily familiar with basics. There are antenna simulation programs out there but they all require that one comes up with a design first in order to calculate the electrical properties such as impedance, radiation pattern, etc..
The first paragraph of Mr RCs last post is probably the only way in lieu of taking a few lower level college courses in RF Engineering that you'll be able to understand the theory of antennas as applied to microwave frequencies.
There are sites out there that deal with microwave antenna theory and design but not at a basic theory level and require at least registration if not a monthly or yearly stipend to access.. Most are University/College web sites.

Mr RC: I'm sure you're familiar with Lee Ciebeks antenna site with his antenna design & theory. His designs & materials seems to have been taken over/aquired by AntenaX & all seem (didn't spend too much time there) to be only available in CD form for dollars now.

[PeterB]

Thanks again. Yes I already listed that article in my previous post.

I loved the way that article elucidated graphically for me the concept of exactly why the impedance changes as you move the probe from one edge of the patch to the other. Check out the figures under the heading Impedance Matching, and the associated text:

"From the magnitude of the current and the voltage, we can conclude the impedance is minimum
(theoretically zero ohms) in the middle of the patch and maximum (typically around 200 ohms, but
depending on the Q of the leaky cavity) near the edges. Put differently, there is a point where the
impedance is 50 ohms somewhere along the "resonant length" (x) axis of the element."

regards
Peter

[PeterB]

Hi Ron,
I had no problems being able to apply it either ! My point was that I had to trust the design had been done right rather than be able to verify the design myself with equations they (didn't) give me. Perhaps if I simulated it myself in the S/W they are advertising I could have done that too.

My main thrust in this thread has been my need to go back to first principles using theory and equations to convince myself that any design I come across has a solid grounding in theory (and/or simulation as appears to be the case here).

I agree with that 1st paragraph too and I might need to embark on that path to satisfy myself.

regards
Peter

Sorry. I had no problem understanding it and getting out of it what was needed to move it to 2.4gc or any reasonable frequency.. I sometimes forget that some who post in this forum are not necessarily familiar with basics. There are antenna simulation programs out there but they all require that one comes up with a design first in order to calculate the electrical properties such as impedance, radiation pattern, etc..
The first paragraph of Mr RCs last post is probably the only way in lieu of taking a few lower level college courses in RF Engineering that you'll be able to understand the theory of antennas as applied to microwave frequencies.
There are sites out there that deal with microwave antenna theory and design but not at a basic theory level and require at least registration if not a monthly or yearly stipend to access.. Most are University/College web sites.

Mr RC: I'm sure you're familiar with Lee Ciebeks antenna site with his antenna design & theory. His designs & materials seems to have been taken over/aquired by AntenaX & all seem (didn't spend too much time there) to be only available in CD form for dollars now.

[Mr.RC-Cam]

I already listed that article in my previous post.

Oops, sorry for the duplicate. I should have checked out your links more carefully. That site seems to have some data that could be helpful to you. From my quick browse, it certainly seemed better than the typical online stuff available in 2002.

In a practical sense, I think you will ultimately find that the information you collect will guide you to a basic design, but will probably not offer all the math to support the principles used. Plus, like many things RF, some of the design details will be up to your network analyzer and perhaps some tedious experimentation.

I really don't have any good tips to offer, other than to get comfortable because you will travel a long journey on your way to patch antenna nirvana. Once you get there, be sure to write a Patch Antenna Book for Dummies. Looks like we could use that!