I know FPV is just underway but I thought posting this in advance might give Fr

[G+_Kellen Razzano]

I know FPV is just underway but I thought posting this in advance might give Fr. Robert Ballecer, SJ??? some ideas to discuss on future episodes. I've been flying RC planes and quads for years so this isn't something new to me; however FPV is. Over the the last year I've been experimenting quite a bit.

 

One challenge that most people will face is limited range when it comes to video signal. A skew-planar or cloverleaf antenna is great for signal integrity however these antennae have an extremely low gain; generally ~1.5dBi, which is lower than even a standard ~2dBi omnidirectional. Paired with a typical entry-level 200mW vTx you'll soon be yearning for longer video range.

 

Here is the $4 solution, and it's glorious. I recently made a 5.8GHz helical directional antenna. I've seen reviews with varying levels of success with using off-the-shelf versions but I believe that's mostly due to quality of materials and attention to accuracy (or lack thereof). It's an antenna -- accuracy is imperative.

* The coil is 10AWG solid-core copper wire that you can buy at most hardware stores for <$1/ft.

* The reflector is a simple copper-clad unprinted circuit board.

* You'll need either a reverse-mount PCB SMA or SMA pigtail (in my case an RP-SMA). Note polarity and gender.

* The frame is 3D-printed and there are many .STLs that you can find on popular sites for free, find one with a regular paper template too for wrapping your coil. (Be sure to match RHCP or LHCP to that of your current video transmitters.)

 

Print out a paper template and wrap it around a 5/8" dowel and then wrap your wire following the lines on the template. This is important as the distance between coils dictates the wavelength and frequency it'll be tuned to. The number of turns (coils) dictate the final gain of the antenna. 5.8GHz can be between 3-turns~12-turns max. Each incremental turn increases the gain but proportionately narrows the band of 'view'. So there's a give and take here and finding a balanced sweet spot is key. You can find detailed specs about this online.

 

I decided to make a 7-turn antenna. I had to pre-drill bigger guide holes (take note of their angles) to accommodate my 10AWG wire. Applying a tiny drop of oil lubricant to each hole will make your life so much easier when feeding and twisting the coil into the frame. Start from the top (tip) and work your way down to the bottom (base), applying a screw-like motion. It's probably easier if you do not glue your frame assembly beforehand, as I did . Continue threading the coil down until its approx 1mm away from the reflector base. Now mark your reflector right below the end tip of the wire. Carefully drill a hole(s) matching the diameter of your pigtail connector and insert. Pull back the shielding shroud and gather it into 2 sections on opposite sides and twist it up tightly. Snip it down to maybe 1mm-2mm to keep it short and then use pliers to smash it flat (you want it flat against the reflector and low to keep it away from the coil). Expose a very small amount of the shielded pigtail tip and line everything up for a dry fitting; adjust as needed. Once you're good break out the soldering iron and tin your pigtail shroud, pigtail tip, wire tip, and 2 spots on your reflector next to the hole. Line it all up and solder the shroud in place, keeping it flat and low, then solder tip to tip. I applied an adhesive-backed zip tie mount on the back of the reflector and zip tied the pigtail to prevent stress or yanking on it. I then used some clear silicone (or hot glue) applied around the backside of the hole and on top of my soldered spots just to protect things. You're now ready to test.

 

I first tested this in my office by having a friend walk the quad around far away and behind obstructions while I monitored from my headset --- WOW! The improvement is beyond words. My previous cloverleaf would begin breaking up and showing heavy static almost immediately once behind a wall and would lose signal once around a corner. Using this helical I was able to see the entire time as he walked around many walls and turned multiple corners across the entire office floor. Occasionally there would be light static but I could still easily see.

 

I encourage people to make one for yourself. My add-on project is now to make an antenna tracker and multi-antenna diversity system on the cheap using arduinos and other small boards. ?

[G+_Jason Marsh]

That looks really nice, but that ProTrack looks sick!!! Somebody drank the whole bottle of awesome sauce when they built that.

[G+_Kellen Razzano]

Wayne Hobbins No, not until now. It seems pretty cool from what I can see. It's basically an EZ-AntennaTracker that uses RSSI instead of GPS, which is appealing.

My idea I mentioned is somewhat similar however it also automatically switches between different antennae. For instance, it might use the directional antenna during distant flight then switch over to a circular-polarized during close-range approach and landings. The idea is to of course use RSSI instead of GPS and to have a simple development board(s) handle all the logic.