HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 15, 2010, 05:06 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
Mini-HowTo
Fast Patch - IBCrazy's easy DIY patch antenna

By request, here is a tutorial on how to build your own patch antenna. As you can see, it's really quite simple and almost anyone can make a good antenna with some basic soldering skills.

If you haven't made your own TX antenna yet, I recommend you build my inverted Vee antenna as in this tutorial: http://www.rcgroups.com/forums/showthread.php?t=1159968 The combination of these two antennas will suit most people's FPV requirements.

In this tutorial I will be building a dynamic patch antenna. I will discuss the basic principals governing the patch and how it works as well as how to adjust and tune it to meet your specific needs. This is different from RC Cam’s Goof Proof Patch, which is also an excellent antenna.
I am constructing this out of 26 gauge galvanized steel, but any conductive metal will work well. Thin galvanized steel (22-30 AWG) works well and can be found for $5-6 at most hardware stores. I bought mine at Lowes in a 12”X24” sheet for $6.

For the bolts and spacers I am using ¼-20 nylon bolts and 1/2 “ spacers. You can use any non conductive bolt or even wooden blocks as spacers.

I will update this thread periodically with more theory and principals later. I will also see if I can model the radiation patterns.

So without further delay, on to the tutorial

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Last edited by IBCrazy; Aug 15, 2010 at 05:17 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 15, 2010, 05:16 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
Calculations: Calculating your length and width

The ½ wavelength measurement:

The first thing you need to do is calculate your ½ wavelength for your frequency. The formula is:

½ Wave in inches = 5124/f in MHz
Or for you metric folks:
½ Wavelength in mm = 130150/f in MHz

This measurement will be the length of your active element. For my 1280 MHz patch, my element is 4-1/16” long.
The length of you element is you ½ wavelength measurement. Now we need to get the width. As the width of the antenna increases, it lowers the impedance of the antenna. However this also changes the radiation pattern. For the patch your width can be anywhere from 3/2 to 4/3 of your length. 3/2 will yield a 50 ohm impedance. 4/3 will yield 75 ohm impedance in theory, but in actuality, it still hits close to 50 ohms. In fact, you can almost make it square. The width affects the radiation pattern more than anything.

So for 50 ohms:
Width in inches = 7686/F in MHz
Or
Width in mm = 195227/f in MHz

For 75 Ohms:
Width in inches = 6832/f in MHz
OR
Width in mm = 173535/f in MHz

Which do you use? It’s up to you. You can pick any value in between those two widths and the antenna will work well. A wider panel will give you a wider beam width but reduce gain slightly. A 50 ohm antenna will have a beam of ~ 90 degrees and a 75 ohm will have a beam of ~75 degrees. Both will work well with your RX. For my 1280MHz I made mine 6 - 1/8” which will give me a wide beam width and an impedance of about 50 ohms.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Last edited by IBCrazy; Apr 04, 2011 at 12:17 PM.
Reply With Quote
Old Aug 15, 2010, 05:19 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
Calculations: Determining your height

Determining you height:

The height of the antenna is entirely up to you. It should be between 1/5" and ½” for 2.4 GHz, between 3/8" and 5/8” for 1.2-1.3 GHz and between 5/8” and 3/4” for 900 MHz.

For my 1280 MHz antenna I chose ½”. Why? Because the hardware store sold ½” nylon spacers which make this really easy

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Last edited by IBCrazy; Mar 03, 2011 at 05:23 PM.
Reply With Quote
Old Aug 15, 2010, 05:20 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
The ground panel

The Ground Panel:
The ground panel is not critical. I recommend you make it square and wider than your width by 4X you height. So for me, I made mine 8”

Simple as that

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Last edited by IBCrazy; Mar 03, 2011 at 05:24 PM.
Reply With Quote
Old Aug 15, 2010, 05:23 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
Assembly: Drilling your holes

Assembly drilling your holes:

Now that you have cut out your elements, now it is time to build your antenna. First you need to drill out a small hole in the active element where you plan to connect your coaxial line. This should be dead center width wise and the same distance from the edge as your height. So for my 1280 MHz patch, this is located at 3-1/16” from either side and ½” from the bottom.

Now you need to drill the holes for your nylon bolts. Where you place them is entirely up to you. I put mine 1” from the corners. Place your active element in the center of your ground panel and tape them together and drill them as one plate. This will ensure proper alignment. Once done, mark your active element hole and drill that such that you can pass the center element of your coaxial line through it.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Old Aug 15, 2010, 05:26 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,352 Posts
Assembly: Constructing the antenna

Assembly – Constructing the panels:

Place your spacers (you can use spacers, washers, or even wood) between your panels, pass your bolts through and secure them. Now make a small solder bead around the coaxial line holes.

Strip your coaxial line and flare out the shield. Strip the insulation off of the top of the center element. Now pass your cable through the backside of the ground panel. Solder the shield to the ground panel and the center element to the active panel.

No go out and try it! The best results will be achieved when the edge of your active element is about ½ wavelength off of the ground. Experiment with this height to achieve best results.

Good luck and have fun! Feel free to post questions and your results.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Old Aug 15, 2010, 05:56 PM
Registered User
Joined Mar 2001
2,624 Posts
Still learning here. What is the purpose of a patch antenna? I regret I never took the time to learn much about electronics. At age 50+ and working to learn about FPV, I may be at a bit of a disadvantage.

Tony
t-turley is offline Find More Posts by t-turley
Reply With Quote
Old Aug 15, 2010, 06:21 PM
Praying for better weather
Coyote64's Avatar
Joined Dec 2007
4,138 Posts
This will teach you loads, very long but shows you the principles of how different antenna works

Antennas 101 - Polarization, Diversity & Gain Patterns (27 min 56 sec)
Coyote64 is offline Find More Posts by Coyote64
Reply With Quote
Old Aug 15, 2010, 07:14 PM
Registered User
Joined Mar 2001
2,624 Posts
Thanks C.

Tony
t-turley is offline Find More Posts by t-turley
Reply With Quote
Old Aug 15, 2010, 08:49 PM
Registered User
Benicia, CA
Joined Jan 2010
26 Posts
Quote:
Originally Posted by IBCrazy View Post
The best results will be achieved when the edge of your active element is about ½ wavelength off of the ground.
I think there was another thread which someone posted this suggestion, quoting you as the source. Is it that the ground acts like another reflector? is this only with patch types? Will it still be a general improvement if the terrain is such that the LOS might be slightly less at the ground instead on on a tripod?
jmg3234 is offline Find More Posts by jmg3234
Reply With Quote
Old Aug 15, 2010, 10:49 PM
Registered User
Ånge Sweden
Joined Dec 2006
133 Posts
I bought a patch antenna that I tried yesterday and it,s crap, itsa 1,2-1,3Ghz patch from rceletronica, my standard wip is alot better.. dont know y?
Unpoor is offline Find More Posts by Unpoor
Reply With Quote
Old Aug 15, 2010, 11:03 PM
The Fixer
Martin Y's Avatar
Canada, ON, Milton
Joined Jan 2009
3,705 Posts
Quote:
Originally Posted by Unpoor View Post
I bought a patch antenna that I tried yesterday and it,s crap, itsa 1,2-1,3Ghz patch from rceletronica, my standard wip is alot better.. dont know y?
What type of connector? Sma or rp-sma? If you have a multimeter test the connector from the pin to ground. Should be infinite resistance
Martin Y is offline Find More Posts by Martin Y
RCG Plus Member
Latest blog entry: Flyfly Fox Glider
Reply With Quote
Old Aug 15, 2010, 11:25 PM
Flying FPV from the lab.
aaron_gx's Avatar
Canada, AB, Lethbridge
Joined Jun 2008
2,090 Posts
Quote:
Originally Posted by Unpoor View Post
I bought a patch antenna that I tried yesterday and it,s crap, itsa 1,2-1,3Ghz patch from rceletronica, my standard wip is alot better.. dont know y?
1000's of reasons. could be the center pin on the connector, the element might be damaged, etc etc...

you are aware that patch antennas are directional? Polarization is important unless you have a circular polarized patch antenna.
aaron_gx is offline Find More Posts by aaron_gx
Reply With Quote
Old Aug 16, 2010, 02:09 AM
Registered User
Alcyon13's Avatar
France
Joined May 2010
537 Posts
Wow thanks IBcrazy !
I'll do it soon, just need to find a galvanized steel.

All my antennas will be from IBcrazy, do you have some stickers ??
Alcyon13 is offline Find More Posts by Alcyon13
Reply With Quote
Old Aug 16, 2010, 02:38 AM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
14,508 Posts
Any changes if using raw PCB board instead ?
renatoa is online now Find More Posts by renatoa
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Patch antenna connector wrong Kmart FPV Talk 12 Aug 11, 2010 12:12 PM
Discussion Patch Antenna Questions dmastax1x FPV Talk 4 Aug 02, 2010 08:25 PM
Discussion Where's the best spot for my patch antenna? mrleenagle FPV Talk 3 Feb 01, 2010 10:12 PM
Discussion DIY Patch Antenna - 900mHz - how to? hurleybt FPV Talk 3 Jun 19, 2009 05:21 PM
It's Cheap, Easy and Fast - It's a blue flying triangle. jastown Parkflyers 3 Jul 30, 2001 04:38 PM