Today I changed the SAW filter on my Lawmate 1.2GHz receiver.
The lawmate receiver is nice and compact…Continue Reading
Lawmate SAW filter upgrade
![post](https://rcexplorer.se/wp-content/uploads/2012/09/spw15-2.jpg)
The Skew-Planar Wheel FPV Antenna
The The Skew-Planar Wheel antenna was brought to the FPV community by IBCrazy. Thank you for making circular polarized antennas accessible to the average FPV-flier.
Never heard about circular polarization? Read about the advantages of circular polarization here
The Skew-Planar Wheel is very alike the Cloverleaf antenna, but instead of 3 lobes it has 4, positioned at 90° apart from each other.
The Skew-Planar Wheel is best suited for the receiver, but will work pretty well as a transmitter antenna as well. It has an excellent radiation pattern and very low gain. The reverse polarization rejection pattern is much better and more uniform than the Cloverleaf, making it excellent for the receiving end. The lowest SWR possible is 1.2.
Gain: ~1dBi
Lowest SWR possible: 1.2
Directionality: Omnidirectional
Difficulty to make: High
Best suited for: Video receiver
Downsides: Hard to make, comparably fragile, big, not very aerodynamic, not possible to trim to the right frequency.
Upsides: Pretty wide band, good radiation pattern, low dBi, good reverse polarization rejection.
You need:
Stiff wire that is easy to solder.
RG316 coax cable.
(The antenna on the pictures in this guide is left hand polarized)
I use 0.8mm copper plated MIG welding wire. It’s stiff and holds its shape well. Yet it’s not to hard to work with in terms of bending and shaping and it’s really easy to solder. Therefore a good choice.
Start of by straightening the wire. Then using a wire cutter, cut 4 pieces of wire a little longer than the calculated length you got from the calculator above. Sand the ends of the wires down using sandpaper, a dremel or a file to the exact length. This technique is the best I’ve tried as trying to cut the wire to the exact right length with just a wire cutter is nearly impossible. Plus it doesn’t make a clean cut. Cutting a little longer than sanding it makes the ends nice and clean.
Now we are going to bend both ends 90° inwards creating a “U” shape with a flat bottom. The length at which you are going to bend is 1/4 wavelength from the ends of the wire, and can be calculated here:
A tip on how to get good precision and speed up the bending is to use pair of calipers. Set the caliper to the length you wish to bend but subtract half the thickness of the wire. So if you’re going to bend at 59.96mm then set the calipers at 59.56mm if you’re using a 0.8mm wire. Place a pair of pliers on the inside of the calipers measuring arm and grab the wire and bend it. Perfect results every time.
Here is one of the “U” shaped pieces. This one is a little croocked (demonstrated here by mr jelly frog). If this happens, don’t worry, simply grab both 90° bends and twist them.
Twist until the piece lies nice and flat agains the table.
Now it’s time to create the arc. The easiest way is simply using your hands and bend it to the right shape. The two tips should meet at a ~105° angle. They could not and should not meet at 90°.
Grab the wire at the 90° bends and bend them until they meet.
If you bend it a little to far the arc is going to look like the one on the right. Don’t worry we’ll fix that.
Here is the ~105° angle visible. This is what we’re aiming for.
To fix the over bent arc simply grab it between you index finger and thumb and squeeze while pulling. Be careful to make the curve as uniform and well shaped as possible.
Repeat with the other three pieces.
Now it’s time to strip the coax cable. I highly recommend using RG316 as it’s much more heat resistant than RG58. Soldering this antenna can be quite a challenge and you don’t want the coax to melt on top of everything.
I use a scalpel to remove the plastic.
Be careful not to cut to deep and damaging the shield. A tip is to bend the coax while cutting. This way you’ll notice when the plastic is cut before you’ve cut too deep and damaged the shield.
Separate the shield, by unlacing the strands, into 4 pieces and place them at 90°, twist the strands together as seen in picture. Strip the signal as close to the shield as you dare. If this part is to long it’s going to shift the frequency of the antenna. But be sure that the signal and shield can’t connect.
To simplify the soldering I made a simple jig out of food container lid. I fixated the lobes at 90° apart. Also make sure that the lobes are at 45° vertically (see video at the end of the guide for more detailed illustration). I recommend using “poster gummy” (green mass used to fixate posters to walls without using nails). It holds the lobes in place better and is easier to work with.
At this step you also decide which polarization the antenna is going to be. The picture shows a left hand polarized Skew-Planar Wheel. For right hand polarization, simply flip the elements over to the right instead.
Solder the legs to the shield first. Be sure to get it properly soldered. Pre-tin the wire and wrap the shield around the wire. Use extra solder flux if you have any.
The trickiest part of the whole thing is to solder the 4 legs to the signal wire. I usually bend the lobes so that they align perfectly without having any strain on them while soldering. This eliminates the risk of one “plonking” off while soldering. An other technique is to use “helping hands” to hold the wires in place. Just make sure to pre-tin all wires and get a good solid solder joint. This is the part that’s most likely to break on this antenna and if it’s a cold solder joint, it’s going to break really easy.
All soldered up.
Now is a good time to check your angles now. The 90°, the 45° and when looking straight from above the top there should be a ~17° separation between the legs thats soldered to the feed-point and the legs soldered to the shield. (See video at the end.)
I added some hotglue to support the solder joints so that they don’t fatigue or break as easily. Beware that hotglue will shift the resonance frequency slightly. But in my opinion, it’s a small price to pay for added durability.
It’s hard to photograph properly but the top of one lobe and the bottom of the next are ~17° apart. (See video as well)
Here is a video showing the geometry of the Skew-Planar Wheel antenna by Jayzy74
Observe that this video shows a right hand polarized antenna, while the previous pictures in this guide are of the left hand polarized version.
The key to success when making FPV antennas is to be meticulous. The more accurate you can make the antenna the better it will perform. Take your time and don’t rush things. This antenna is well worth the effort.
![post](https://rcexplorer.se/wp-content/uploads/2012/09/cl13-21.jpg)
The Cloverleaf FPV Antenna
The Cloverleaf antenna was brought to the FPV community by IBCrazy. Thank you for making circular polarized antennas accessible to the average FPV-flier.
Never heard about circular polarization? Read about the advantages of circular polarization here
The Cloverleaf is a closed-loop antenna, meaning that the signal and ground wires are connected. Measuring between signal and ground with a multimeter would read a short circuit. However it works great as an antenna. The cloverleaf has 3 lobes at 120° apart from each other in the horizontal plane and angled 45° in the vertical plane. It may look funky, but it’s an excellent transmitter antenna. In fact its one of the best FPV video transmitter antennas out there at the moment.
The Cloverleaf is best suited for the transmitter, and almost exclusively used for this purpose. It has an excellent radiation pattern and very low gain. It’s also possible to achieve a perfect 1.0 SWR, making it very efficient. It is not the ideal antenna to use on the receiver though. The reverse polarization rejection pattern is very erratic and varies between -8 and 19dBi. Therefore there are better antennas to choose for the receiver. This doesn’t matter for transmitting signals though, only for receiving them.
Gain: 1.2dBi
Lowest SWR possible: 1.0
Directionality: Omnidirectional
Difficulty to make: High
Best suited for: Video transmitter only
Downsides: Hard to make, comparably fragile, big, not very aerodynamic, not possible to trim to the right frequency.
Upsides: Possible to achieve SWR of 1.0, pretty wide band, good radiation pattern, low dBi
You need:
Stiff wire that is easy to solder.
RG316 coax cable.
(The antenna on the pictures in this guide is left hand polarized)
I use 0.8mm copper plated MIG welding wire. It’s stiff and holds its shape well. Yet it’s not to hard to work with in terms of bending and shaping and it’s really easy to solder. Therefore a good choice.
Start of by straightening the wire. Then using a wire cutter, cut 3 pieces of wire a little longer than the calculated length you got from the calculator above. Sand the ends of the wires down using sandpaper, a dremel or a file to the exact length. This technique is the best I’ve tried as trying to cut the wire to the exact right length with just a wire cutter is nearly impossible. Plus it doesn’t make a clean cut. Cutting a little longer than sanding it makes the ends nice and clean.
Now we are going to bend both ends 90° inwards creating a “U” shape with a flat bottom. The length at which you are going to bend is 1/4 wavelength from the ends of the wire, and can be calculated here:
The three “U” shaped pieces
A tip on how to get good precision and speed up the bending is to use pair of calipers. Set the caliper to the length you wish to bend but subtract half the thickness of the wire. So if you’re going to bend at 59.96mm then set the calipers at 59.56mm if you’re using a 0.8mm wire. Place a pair of pliers on the inside of the calipers measuring arm and grab the wire and bend it. Perfect results every time.
Now it’s time to create the arc. The easiest way is simply using your hands and bend it to the right shape. The two tips should meet at a ~105° angle. They could not and should not meet at 90°.
Here is the ~105° angle visible. Be careful to make the curve as uniform and well shaped as possible.
Repeat with the two other wires as well.
Now it’s time to strip the coax cable. I highly recommend using RG316 as it’s much more heat resistant than RG58. Soldering this antenna can be quite a challenge and you don’t want the coax to melt on top of everything. Separate the shield into 3 pieces and place them at 120°. Strip the signal as close to the shield as you dare. If this part is to long it’s going to shift the frequency of the antenna. But be sure that the signal and shield can’t connect.
To simplify the soldering I made a simple jig out of food container lid. I simply taped down the lobes at 120° apart. Also make sure that the lobes are at 45° vertically (see video at the end of the guide for more detailed illustration). I recommend using “poster gummy” (green mass used to fixate posters to walls without using nails). It holds the lobes in place better and is easier to work with, but I didn’t have any at home at the time of this build. Notice the hole in the bottom. That is where the coax cable is fed through and soldered in place.
At this step you also decide which polarization the antenna is going to be. The picture shows a left hand polarized clover. For right hand polarization, simply flip the elements over to the right instead.
Solder the legs to the shield first. Be sure to get it properly soldered. Pre-tin both the wire and the shield. Use extra solder flux if you have any.
The trickiest part of the whole thing is to solder the 3 legs to the signal wire. I usually bend the lobes so that they align perfectly without having any strain on them while soldering. This eliminates the risk of one “plonking” off while soldering. An other technique is to use “helping hands” to hold the wires in place. Just make sure to pre-tin all wires and get a good solid solder joint. This is the part that’s most likely to break on this antenna and if it’s a cold solder joint, it’s going to break really easy.
Check all your angles now. The 120°, the 45° and when looking straight from above the top there should be a 10° separation between the legs thats soldered to the feed-point and the legs soldered to the shield. (See video at the end.)
I added some hotglue to support the solder joints so that they don’t fatigue or break as easy. Beware that hotglue will shift the resonance frequency slightly. But in my opinion, it’s a small price to pay for added durability.
Really neat looking antenna. People will think you know what you’re doing if you use on of these.
This antenna was measured to 1.05 SWR which made me really happy.
It’s hard to photograph properly but the top of one lobe and the bottom of the next are 10° apart. (See video instead!)
Here is a video showing the geometry of the Cloverleaf antenna by Jayzy74
Observe that this video shows a right hand polarized antenna, while the previous pictures in this guide are of the left hand polarized version.
The key to success when making FPV antennas is to be meticulous. The more accurate you can make the antenna the better it will perform. Take your time and don’t rush things. This antenna is well worth the effort.
Cloverleaf antenna guide
Here is the first circular polarized antenna guide in the series, the Cloverleaf. Currently one of the best transmitter antennas out there the Cloverleaf is the natural choice for your FPV platform. Read the guide, build the antenna and be amazed.
Chat log from 28/8 -11
Another great chat guys. I really enoy catching up with all of you from time to time and help out anyone in need.
Here is the chat log for everyone that couldn’t make it.
Will announce next chat ASAPContinue Reading
Flying High
- Airframe: Tricopter V2.5
- Stabilization unit: KK
- RC TX: Hitec Aurora 9 2.4GHz AFHSS
- RC RX: Hitec Optima 9
- Camera: GoPro Hero HD set at 720p 60FPS
- Video TX: 1.3GHz 300mW, Cloverleaf antenna
- Video RX: 2 x 1.3GHz Lawmate
- Video RX 1 antenna: Skewplanar wheel
- Video RX 1 antenna: Helical
- Diversity controller: Eagletree Eagle Eyes
New video! – “Flying High”
Two days of editing and many days of shooting has produced these results:
Trivia:
The video was filmed in California, Florida, Ohio and the middle of Sweden. Which is by far the furthest distance per scene I’ve filmed so far.Continue Reading
Working on a new video
Hey guys! Just wanted to let you know that I’m editing a new video. It’s planned to be released this week. Here is a teaser shot:
I’m also working on the new antenna tutorials. Stay tuned!
Chat log from 21/8-11
Great chat yesterday guys! Thanks for dropping by and chatting a bit.
Here is the chat log for everyone that couldn’t make it.Continue Reading
MiniQuad update #7
After flying the MiniQuad for a while I decided to increase the prop size. But then I ran into some trouble, the carbon tubes twisted under heavy load. To fix this and also make it more impact resistant, I added a carbon square frame.