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Archive for the ‘Radio’ Category

Video Downlink for KAP

Posted by Tom Benedict on 04/12/2013

This is the third and final installment of KAP articles. In Then and Now I described the evolution of my KAP rig from my first flight to the rig I use regularly today. In A Progression of Kites I described the additions I made to my kite bag over the years, and what those kites provided for in terms of KAP. This article describes my video downlink system.

The previous two articles were written almost as a history: “First this happened, then this happened.” But over the years as I solved the various problems I ran into with my video downlink system, I wrote articles describing what I did. So the history version of this has already been written. Rather than repeat what I wrote, this article is more of a how-to for adding a video downlink system to a KAP rig.

In its very simplest design a video link is a wire that connects the video output of a camera with the video input of a display device. It’s possible to set up a KAP rig this way, but the wire would have to be long, heavy, and would be a nasty thing to have in your hand when lightning strikes. For obvious reasons, it’s preferable to send the video signal to the ground some other way: radio.

It bears mentioning at this stage that unlike a wire, leaping into the world of radio places the operator in a new situation. At this point you’re transmitting your signal in such a way that it can potentially interfere with other wireless devices. In most countries radio transmitters are regulated, and typically fall into two categories: Either the device has been declared fit for use by an untrained person or it has not. In the US this declaration comes in the form of FCC Part 15 approval. If the device has an FCC Part 15 sticker on it, you can use it without a license. If it doesn’t, you can’t. The laws in other countries will vary, but that’s how it is here.

FCC Sticker

As was pointed out to me when I started down this road a couple of years ago, if you wind up using equipment that doesn’t carry your country’s seal of approval, it’s up to you to get whatever licenses are necessary for you to stay on the right side of the law. Unfortunately most video transmitter gear requires a license. (In case you’re wondering, that’s a picture of a 2.4GHz transmitter module from an RC radio. Most RC gear is approved for unlicensed use. The manufacturers are well motivated to make sure their stuff is certified. Video manufacturers? Not so much.)

There’s another benefit to studying for and getting your radio license. The whole point of the exercise is to give you the information you need to successfully and safely experiment in the world of radio. And that’s precisely what you’re doing! You’re exploring the world of radio by setting up an amateur TV station and a receiver. Questions that you’ll need to answer will include how much power to use, what kind of antenna to use, how much radiation exposure you’ll get, etc. By virtue of studying for and receiving your amateur radio operator’s license, you’ll find the answers to these and other questions. It’s well worth it.

Back to the video link!

The next question you’re probably asking is, “But what do I have to get to make it work?” Unfortunately there’s no right answer because there’s more than one way to do it. Here are some things to consider:

Most video hardware is built to handle either NTSC, PAL, or both of these formats. When looking at your gear – camera, video transmitter, video receiver, and monitor – keep in mind which system you’re using and make sure all your hardware will handle it. I got hardware that will handle both, so I can switch the entire setup from NTSC to PAL and back without penalty.

All of this hardware will have to be powered. In the world of FPV RC aircraft, there’s an advantage to running your video system on a completely different power supply than your radio system. That way when your video system drains your batteries dry, your aircraft doesn’t suddenly fall out of the sky in an uncontrolled heap. This isn’t as big a consideration in the world of KAP since the kite will fly regardless of the state of the batteries. (A single line kite with a dead battery flies exactly the same as a single line kite with a fully charged battery. The kite really doesn’t care.) So there’s an advantage to choosing gear that can all be powered off of a single source.

Between the transmitter and the receiver you will need a pair of antennas. At their simplest an antenna is a piece of wire trimmed to a particular length (1/4 the wavelength of the transmitted signal). At their most complex they can be fairly complicated pieces of equipment that preferentially transmit and receive in a particular direction, polarize the signal in a particular way, etc. Keep in mind that the size of the antenna is always dependent on the wavelength of the transmitted signal.

And while keeping that in mind, consider that radio gear for sending and receiving video signals can be built to operate on a wide range of wavelengths. At the longer end of the spectrum (literally) you can get 900MHz hardware. At the shorter end you can get 5.8GHz hardware. In between you can find hardware built to 1.2MHz, 1.3MHz, 2.4MHz, etc. The longer your wavelength, the better the signal will penetrate solid objects and bend around corners, and the less power it will take to get a particular range. This favors longer wavelengths. Conversely, the shorter your wavelength, the smaller your antenna. This favors shorter wavelengths. And no matter what, you don’t want your video system to interfere with your RC transmitter, either at the primary frequency or at a harmonic (n * freq). So if you’re using 2.4GHz RC gear, don’t use 2.4GHz or 1.2GHz video gear.

Finally, you’ll need some form of display on which to see the image from your camera. Options for this range from fully enclosed headsets like the ones from FatShark to standalone monitors. The display you choose will depend greatly on what you’re doing.

Regardless of whether you’re planning to build a video downlink for KAP or an FPV setup for RC aircraft, it’s really not safe to use a self-enclosed headset if you plan on operating your gear by yourself. The AMA’s safety guide for FPV specifically says you should use a spotter when flying FPV, and that they should maintain line-of-sight on the aircraft at all times. It’s really no different for KAP. If you’ve spent any amount of time flying single line kites, chances are you’ve seen them do something unexpected. If you’re watching the kite you can typically do something to recover. If you’re staring into a self-enclosed headset, you won’t notice until it’s way way too late. If you plan to use a headset for KAP, also plan to bring someone along to operate the kite. I’m a solo KAPer, so I built my system to use a monitor.

Something to look for when getting a monitor is what it does when it loses signal or encounters a glitch. Many of them switch to a blue screen. Because radio signals are almost always glitchy, this means that the monitor will spend most of its time being blue. Look for a monitor that will show static when it loses signal or encounters a glitch. Most of the ones that do will proudly tell you of this on the packaging or in the advertisement, and may even say, “Made for FPV use!” My first two monitors did the blue screen thing. Skip the pain and get a good monitor from the get-go.

Now for the real question: How do you wire all this stuff together? Fortunately the world of FPV has made these systems a lot more turnkey than they used to be. Unfortunately they’re not as turnkey as, say, plugging servos into a receiver and moving them with joysticks. Some soldering is typically required. Here’s the diagram for the system I built using Boscam 5.8GHz hardware:

FPV Wiring Diagram

I used a 3-cell LiPoly battery to power the video system, so the video transmitter is getting between 12.6V and 11.6V. The UBEC steps that down to 5V for the RC receiver and servos. I don’t use the Vcamera output on the transmitter to power the camera, and rely on the camera’s own internal battery for its power.

Keep in mind this is for a KAP system. I built out a similar system for FPV. In that case I omitted the UBEC and didn’t provide any connection between the video system and the RC system. This was in order to avoid RF interference from the airplane’s ESC, motor, and servos, and to keep the video system from draining the flight battery, as I said earlier.

When setting up your radio gear, carefully check the channels the gear can operate on to make sure the frequencies are legal in your country. Not all countries allow amateur use on all bands, and not all countries define the bands the same way. You should be able to find the frequencies used for each channel in the manual for your hardware.

When setting up the channels on mine I ran into another problem: The Boscam 5.8GHz Rx and Tx use banks of DIP switches to set the channel. Unfortunately on one of them 1 is up and 0 is down, and on the other 1 is down and 0 is up. Even worse, the setting for channel 1 on the transmitter and the setting for channel 1 on the receiver are completely different! So for those using the Boscam 5.8GHz system, this diagram appears to be correct if you are looking at the numbers on the DIP switch banks (original source):

Boscam VTx VRx Channels

Because I knew I wanted to be able to swap cameras on my KAP rig, I wired the three video/audio/ground wires to a male servo connector and built individual camera cables that ended in female servo connectors. To swap cameras, all I have to do is swap cables.

Quick aside: If you plan to do anything with any sort of servo gear – KAP, RC airplanes, robotics, whatever – get a bag of male connectors, a bag of female connectors, a spool of servo wire, and a crimp tool. Places like Servo City carry these as stock items. I have never regretted getting mine. The only regret I’ve had is that I didn’t get bigger bags of connectors! You’ll find these come in handy for more than just servos.

Ground stations vary from person to person. I built mine for KAP, so it’s small, self-contained, and can be attached to my RC transmitter.

KAP Video Ground Station Rear

I use the same ground station for FPV. It consists of the video receiver and antenna, a monitor, and a battery. The wiring is typically a little more straightforward than on the transmitter gear. Both video receiver and monitor usually come with RCA connectors, so it’s just a matter of plugging everything in. In my case, though, the RCA cables were all male! Rather than use a bunch of female/female gender changers to connect the cables together, I made all new cables. But it’s not necessary to go this far with your gear.

Once you have all your bits and have wired them together, test it thoroughly on the ground. Having a KAP video downlink fail in the field is a bummer, but it’s not the end of the world. Most of us start off either using autoKAP or aiming by looking up at the camera, so not having a video downlink isn’t a show-stopper. It’s just not fun. If you’re building out an FPV link for an RC aircraft, losing your video feed mid-flight can be a lot more disorienting and may lead to a crash. So test first. Then test again. Then, just for grins, test it again. I spent way too many KAP sessions chasing video problems to chance it these days.

Whatever route you go, remember to fly safely whether you’re flying a kite, a plane, a helicopter, or a multi-rotor. Using a video downlink of any sort means you’re taking your eyes off of your aerial platform. In the case of a kite, finding it again is just a matter of looking up the line. In the case of an airplane or helicopter, it may take you a while to pick it out of the sky. Use a spotter. And expect things to go wrong. They always do.

– Tom


Posted in Electronics, Engineering, Kite Aerial Photography, Radio, RC Airplanes | Leave a Comment »

New KAP Ground Station

Posted by Tom Benedict on 27/05/2013

Earlier I mentioned I’d picked up a 7″ Feelworld LCD monitor to rebuild my KAP video downlink. I finally got around to building the ground station to go around it.

KAP Video Ground Station

The heart of it is that 7″ Feelworld LCD. These are meant for wireless video, so they don’t switch to blue screen when the signal glitches, or assume the signal format has changed, and try to automatically re-negotiate PAL vs. NTSC. Those settings are manually done, and if you get static in your signal, you get static on your screen.

The larger size is also easy to see without wearing my glasses. I’m far-sighted, and old enough now that my near vision requires me to use glasses to read. Even using my phone without glasses can be troublesome. My older monitor was nice and compact, but difficult to see without putting on glasses. Unfortunately, once I put them on everything beyond about thirty feet goes blurry. This means I can’t see my kite with my glasses on, and couldn’t read that tiny monitor with them off. But the larger screen on this monitor is easy for me to see, with or without glasses. Problem solved.

I wanted the whole ground unit to be a single compact brick I could mount to my KAP transmitter, stick on a tripod, hand to someone, etc. It required some modifications, but they worked out well.

KAP Video Ground Station Rear

The monitor had a 75mm VESA mount on the back, to allow it to be used with VESA accessories. I made a backer plate for the monitor to house all the stuff I wanted to use with it, and popped four holes on 75mm centers so it could be bolted straight to the back of the monitor without modifying anything. The backer plate houses the 5.8GHz receiver – and doubles as a heat sink for it, and also contains the battery and the main power switch.

The battery is a 2.65mAh 3S LiPoly that was designed for use in an RC transmitter. It’s a 1C battery, so it can only source 2.65A. But the current draw on the monitor and video receiver are so low, I’m not even close to this value. It should provide plenty of juice for a full day of KAP, and charges in about 20 minutes.

I was on the fence about adding the power switch until I tried plugging in the battery and mounting it to my KAP transmitter. Bleah! Talk about awkward. The switch took less than half an hour to pop in, and makes it way more convenient to use.

KAP Video Ground Station Battery Compartment

The battery is held in place with nylon webbing stitched to industrial strength Velcro. The entire battery compartment is lined with fuzzy Velcro for cushioning, and the strap extends almost the entire length of the battery. Plenty of grip to keep things in place in the field. I added a finger tab at the end to make it easy to pull off to get the battery out for charging. (Never ever charge a LiPoly battery in the device!)

KAP Video Ground Station Bottom

In addition to the VESA mount, the monitor also included a 1/4″-20 threaded hole for mounting to a tripod, and a T-slot for mounting to some other rail system. The T-slot worked great on the mounting arm I’d already stuck on my KAP transmitter, so that’s the one I chose to use. But I left the 1/4″-20 socket exposed as well in case I want to mount it to a tripod for easy-chair KAP.

All in all the ground station has worked out great. The reception is far better than with the old system, and since the video doesn’t glitch every time there’s static in the signal, the usable range is huge – far larger than I really need for a KAP video downlink.

Which takes me to the other reason I wanted this to be a removable, stand-alone handheld system: It’s pretty trivial to get a second video transmitter and stick it in an RC airplane. Aaaaah! More fun!

– Tom

Posted in Engineering, Kite Aerial Photography, Radio, RC Airplanes | 1 Comment »

Scary, Smart, Loud ‘n Clear – My Weekend

Posted by Tom Benedict on 20/08/2012

Sorry, no good machining stories or photography stories from the weekend. I did start drawing up the main halyard winch from our Pacific Catamaran in the hopes of building a new one, but it also looks like I can press the old one back into service with a little work. And I brought my KAP gear to the beach on Sunday, but didn’t put a camera up. Still, the weekend wasn’t without story material:


Saturday morning, we decided to pick up all the toys in the yard, clean up the porch, basically de-redneck. (No, my Jeep is not up on blocks yet, but that’s another story from the weekend.) My son grabbed all the slippers and crocs from the back porch and took them inside to clean. Why he brought them inside to clean in the bathtub instead of using the hose outside, I’ll never know. But he did. And somehow I wound up having to clean the tub, not him. (Go figure…)

About halfway through, the screaming started. Loud screaming. Screaming with purpose! That could mean only one of two things. I tore off running for the bathroom. “What happened?!” I yelled.

I saw a brown widow spider!” my son replied.

I took two things away from this: One, there was a brown widow in my bathroom – my son knows full well what they look like. Second, he saw it, but wasn’t bit by it. WHEW!

In case you’re not familiar with brown widows, they’re quite similar to black widows. Their bite packs only a slightly less mighty wallop than the bite of a black widow. For a kid his size, it would’ve meant an ER visit at the very least. And yeah, the place where we live is rife with them. Normally when we encounter a stray animal in the house, we stick it in a container and take it somewhere safe for the animal to be released. But I draw the line on centipedes and brown widows. My younger daughter teared up when I flushed it, but down it went. I breathed a sigh of relief. So did my son.


Some months back the left side mirror on my Jeep fell off. The pivot had rusted through, and it just flopped off on the ground one day. There was no way to put it back together, so I ordered a new pair of mirrors off an online Jeep parts retailer. The new mirrors came in a few days, and… there were no instructions. I looked through my repair manual. No help there, either.

From what I could see, they screwed in from the inside of the door. ??! The inside? How the heck was I supposed to do that? I looked at the door, but didn’t see any real way to get at the screws. So I tossed the mirrors in the back of my Jeep and learned to drive with two out of three mirrors. For the record, no, this isn’t safe. And no, it’s not smart. And actually, I’m pretty sure I could’ve been pulled over for it. But my options were starting to look like removing the door panels, taking out the windows, and then drilling through the inside of the door since there was no other way to get at the screw heads. I figured I could wait on it until my next safety inspection.

Which, of course, came due in August. Oh wait! It’s August! And just in time, my car blew a turn signal bulb, lost most of its brake fluid, and came due for an oil change. It really does hate me. I swear it does. But I love it anyway. So Rydra and I drove to NAPA and picked up stuff for an oil change, air filter change, a new set of bulbs, and brake fluid. When we got home she said, “You need to replace that mirror if you want to pass inspection.”

“Yeah, I have them right here.” I showed her where they’d been living in my car for the last few months.

“Why haven’t you put them on?” she asked.

I went into the whole song and dance about how I’d have to take my doors apart, maybe drill into them, etc. I sounded like a total whiner, I’m sure. She stared at me through all of this, then proceeded to show me how the covers snap on and off of the things so you can get at the screw heads really easily, because they’re on the outside of the door where a sensible person would put them. What I had been struggling with for months, she figured out in under ten seconds. >sigh<

(Now do you see why I get frustrated when we can’t find any women applying for our telescope engineer positions!)

She graciously helped me install my new mirrors, and stood by while I topped off the brake fluid. “Why was your fluid low?” she asked.

“I don’t know,” I replied.

As she walked inside she said, “I’d look for a leak if I was you.”

I looked under the car. Brake fluid was oozing out of my left rear brake. >sigh< One more repair on the list: rebuilding the rear brakes.

Loud ‘n Clear

After the whole “let’s work on the Jeep!” fiasco, we headed down to the beach. I love going there. It helps that Hapuna Beach, one of the top ten rated beaches in the world, is less than fifteen minutes from our house. I also just never run out of stuff to do there. From swimming to boogie boarding to diving off the rocks, it’s a great place to go. Of course half the time I do none of those things because I’m doing something else. Reading a book, flying a kite, doing kite aerial photography, it’s all fair game.

Hapuna A650 July, 2011

This time I brought my KAP gear, but I brought something else as well: a shortwave radio. I’ve had one for ten years or so. But ever since getting my ham license, it’s been something of a tease. “Here! You can listen, but you can’t taaaaalk! Hahahaha!” Yeah, whatever. But until I have my General license and an HF rig to use, it’s as close to the longer bands as I’m going to get. Like the song goes, it’s not having what you want, it’s wanting what you’ve got. So rather than stress it, I’ve been having fun with it.

But a radio is nothing without an antenna. And often it’s the antenna that makes the real difference, not the radio. So some months back I started looking into what I could do to improve the reach of my shortwave. The idea is pretty simple: Run three wires in parallel, each of a different length, and connect them all at one end. Make the lengths right, and you have a multi-band antenna. I got the idea from this site. (Yes, yes, the site calls for four wires. I only had three-conductor wire on hand, so I lost one of the bands. It’s still pretty darned cool!) But rather than hang this from a tree or a post, as in the article, I suspended it from a kite line. A ground wire running down into the wet sand let me use the beach and ocean as my ground plane.

The antenna went together in an afternoon, and was easily rolled onto an old kite line spool I had lying around. And that’s where it sat for a long, long time. We had stopped going to the beach for a while, so I didn’t have reason to pull it out. This time, I was pulling it out!

The antenna weighed less than my DSLR KAP rig, so I knew the kite would lift it. Once it was airborne, I clipped the antenna on and let line out to hoist it up. Every ten feet or so I had another clip so the kite line would support the antenna for its full length. When the entire antenna was up, I tied off the kite line and set the ground spike in the sand. Then I plugged the antenna into my radio and turned it on.


I had no idea the radio waves were that jammed. I picked up China easily, then picked up several Australian stations. Next was a whole set from South America (though my Spanish is too poor to figure out which ones). Next was Japan. These were all incredibly clear. It didn’t even qualify as DX the signal strength was so high. I thought I heard one that was either German or Dutch, but I couldn’t be sure. Just to make sure the antenna was actually doing something, I unplugged it. (It’s a receiver, so no chance of a blown output amplifier stage.) Dead silence. I plugged it back in, and WHAM! Everything was back.

We had to leave well before I was done scanning all the bands my antenna gave me. I didn’t even take notes on which stations I’d picked up. There were just too many. I’ll be more systematic next time. I swear.

When I got home, I did some poking around just to see what it would take to do this with an HF transceiver. As it turns out, not much. Since this was a receive-only antenna, I got away with using very lightweight wire. But MFJ makes a multi-band center-fed dipole that looks like it would hang from a kite line, too. The antenna is rated for 1500W of transmitter power. I doubt I could find an HF rig that would fit in a backpack that could even come close to that. So the antenna problem is solved.

Just more incentive to hit the books and get my General license. Meanwhile, I’ve got something new to do at the beach on the weekends.

– Tom

Posted in Engineering, Hawaii, Kite, Kite Aerial Photography, Radio | 5 Comments »

Life’s a Beach

Posted by Tom Benedict on 22/02/2012

I didn’t get to pull out my 4×5 camera this past weekend. By Friday afternoon it was pretty clear I’d caught a cold. So I spent most of the weekend indoors wishing I could be outdoors. By Sunday afternoon, however, I was ready to risk anything to get out of the house. So we went to the beach. I came prepared!

Most of the time when I go to the beach I’ll either pack my KAP gear or I’ll pack a book and a beach chair. This time I brought my KAP gear, all my kites, a two-line kite (a Jon Trennepohl Widow), the full-spectrum Canon XT I have on loan, my shortwave radio, a long-wire antenna, and my book. But no beach chair. I figured if I needed to sit down, I could just flop on the sand.

The wind was perfect. So while everyone else was taking off their sandals to get in the water or setting up their chairs to read by the seaside, I was muttering under my breath about not wasting good wind and trying to get everything set up in the shortest amount of time possible. Up went the 6′ rokkaku, out came the rig and transmitter! I got my T2i airborne with the video down-link, and got down to business.

Blue Umbrellas

The wind was a little stiffer than I liked, but other than that conditions were perfect. The sky was a little hazy, but not so much that I didn’t get good shadows. The video link worked like a charm. I was able to compose a number of photographs that I knew I’d like when I got home. I exposed 39 frames — a far cry from the hundreds I typically do when not using a viewfinder. Of those only a couple were real tossers. It was a matter of choosing the best rather than choosing not-the-worst.

Sand Play

I brought my T2i down and switched to the full-spectrum Canon XT. I stuck my Hoya R72 filter on the end of the lens and did some IR KAP.

Hapuna Prince Resort in the IR with Kohala

I was really pleased to see how well the IR cut through the haze in the air. This is typical of IR photography, but it’s neat to see it when it happens. In the distant background you can see individual clumps of trees on Kohala Mountain showing up brightly in the near-IR.

The Canon XT doesn’t have live view, so I can’t use the video down-link with it. I was a little surprised to see one of my carefully composed T2i photos and one of the blind-aimed XT photos were almost identical in terms of composition! So I put them together as a visible/IR diptych:

Visible and IR

The card in the XT is fairly small (512MB?) and I had it set to make RAW files, so I knew I couldn’t take too many pictures before the card filled up. Eventually it was time to land the camera and pack the KAP gear away. Then out came the shortwave radio!

Two weeks ago I brought my kites to the local radio club meeting as a sort of show-and-tell. Mostly it was to get the gears turning to see what the club members came up with. A number of people were interested in doing some QRP DX using a longwire vertical. Someone else had the idea of sending up a pair of handhelds, set up as a cross-band repeater. The ideas bounced around faster than I could keep track of them! By the time we left, everyone was making “Hmmm!” noises. It was a fun meeting.

For my part, I wanted to see how a long wire antenna would work out. I don’t have my General license yet, so I can’t transmit on the HF bands. But I can listen! I’ve had battery powered shortwave for the last ten years or so that goes out to 120m. When I bought it I also picked up a 10m antenna. Not ideal for the longer wavelengths, but decent for the shorter ones and better than nothing. Just for grins I tied the antenna to my kite line and ran it up. I couldn’t develop enough height to be too worried about static buildup, so I just plugged it straight in.

And boy did it work! I picked up transmissions from Japan, China, and Australia. I got some others I couldn’t identify, but already that sounded pretty cool. I tried some of the longer bands, but the short antenna just couldn’t pull them in. Besides, I didn’t have a decent ground plane, so I knew I wasn’t getting everything out of it that I could. I packed everything away and started making plans for setting up a quarter wave ground plane antenna that would get me out to 120m. Only this time I’ll add a static discharge resistor!

As I was packing my radio away and landing the rokkaku, I realized the wind was picking up as the sun got lower rather than the other way around. The normal pattern is to have the wind drop off at sunset. Aaaah, but we weren’t having normal weather! (If it’s any indicator, Mauna Kea and Mauna Loa had a snowstorm Saturday night.) So I pulled out the two-line kite.

I fly our Widow, but really it’s my wife’s kite. I’m more of a single-line guy. She saw me throw it in my kite bag when we were packing for the beach, but didn’t say anything. As we were driving down I asked if she’d be interested in flying it. She looked a little pained, but shook her head. Ever since her brain surgery, she’s had a hard time adjusting to the loss of her stereo vision. She explained that she was worried she wouldn’t be able to fly it with one eye. I thought otherwise, but I held my tongue.

Once the Widow was airborne, though, I had to see her try. It was good clean wind, the sand was clear for most of the window, and I could see her watching out of the corner of her eye. So I waved to her and gestured for her to come over. She stepped in, took the handles, and flew it just as she always had.

Back In Command

Eventually she had a hard landing in the sand that busted a spar. I didn’t care. A busted spar can’t hold a candle to the look on her face. It was great to see her at the controls again.

As the evening drew to a close I put up the PFK Nighthawk that Pierre Lesage and Heidy Baumgartner gave me when they visited Hawaii about a  year ago. The wind was really too light for it to do any lifting, but you just can’t beat the wind range on that kite. Pierre has used one to fly a camera in 45 knot wind. I was flying mine in less than five knots. On a whim I decided to re-create a photograph I’d made during Worldwide KAP Week 2009.

PFK Fine Guidance System

I’ll get out with my 4×5 next weekend. For now life’s pretty good.

– Tom

Posted in Kite, Kite Aerial Photography, Photography, Radio | Leave a Comment »

A Second and A First

Posted by Tom Benedict on 11/02/2012

I got out again at lunch today and flew my video assisted KAP rig for the second time. But before I did that I flew my first IR-converted camera.

The camera is a full-spectrum modified Canon Rebel XT. The conversion was done by a guy at work who did the conversion for the CFHT Cloudcams. (The camera I used is actually a backup cloudcam.) The conversion involved removing the camera’s IR blocking filter from the front of its detector, and replacing it with a piece of BK7 glass. This lets infrared light reach the camera’s detector, but still maintains the same optical depth so that the autofocus hardware in the camera still works.

The flight itself went great. It flew exactly like an unconverted camera, except I couldn’t use my video down-link with it. The camera predates live view on the Canon DSLRs. So it was back to aiming by eye. I came away with some keepers, so I’m pleased.

CFHT Headquarters in the Near IR

The flight took place near the headquarters of the Canada-France-Hawaii Telescope Corporation where I work, which is the subject of the photo. No, it’s not snowing here. That’s grass on the ground.

The camera focuses like a champ, but the exposures aren’t quite on. My guess is the exposure sensors have a different response to infrared light than the focal plane detector. For this flight I metered manually, but I think a better approach in the future would be to figure out what the exposure offset is and just dial it in with exposure compensation.

Once the IR camera was safely landed and put away, I stuck my T2i on the rig and plugged in all the video hardware. The wind was stronger than during my first flight, so no surprise landings. But it was also more turbulent. So getting the compositions I was after was harder. Still, it worked out well. Here’s the visible light version of the above photograph from a slightly different vantage point:

CFHT Headquarters

I wanted to get the whole building in the frame without the foreground building intruding, but the wind wasn’t cooperating. Still, this was a nice tight composition. Except for normal RAW processing, this is straight off the camera. No cropping, no rotating, no nothing. I am super super pleased with how well this video downlink setup is working out.

Several years ago when I first flew over CFHT HQ, I did some directly-down photos of the indoor garden and the lanai area. They were completely blind-aimed. For some of them I couldn’t see the building at all, and was going entirely by feel. I got lucky and got some good images. So I tried to do the same with this setup, where I could compose them at will.

The first, the indoor garden, worked out quite well:

Complex Rooflines

Except for a little horizontal perspective control tilt to get my horizontals horizontal, I didn’t do much of anything to this photo. It really was rotated that straight from the get-go. Ok, ok, to be fair the wind was really cooperating for this one. I had plenty of time to half-press and focus, do the final composition, and trip the shutter. Not so for the lanai:

CFHT Lanai

I really wanted this one to be as well-aligned as the previous photo, but the wind was not as cooperative. By the time I’d walked in to position to make this one, the kite was bucking around and the rig was swinging. I could get the focus and composition, but not rotation. Two out of three. If I rotated, the tilting of the rig meant I wouldn’t always get the full courtyard in the shot. I did the best I could and walked away with some good photos. As with the full building photo, this one is almost straight off the camera. Just normal RAW processing. No cropping, no rotation.

Right after tripping the shutter on this one, the wind dropped. Kite and camera started coming down a little too fast for comfort. When I set up I knew that might happen, so I used too much kite for the wind. After the wind dropped I was glad I’d made that call. It was a bit of a mad dash to bring in line and land the camera safely, but everything made it down without a scratch. Camera went back in the camera bag, KAP rig and radio went back in the KAP bag, and the kite went back in the kite bag. With ten minutes left in my lunch hour, time to go back to work.

All in all I’m liking this video down-link more and more. It’s a good direction for my KAP to go. But as I hinted at in my last post, there are some changes I’d like to make to my gear. I spent the last of my earnings from my last Getty sale picking up the hardware I need to get all this done, so it’s not a question of if. It’s a question of when:

  • I’m adding a new switch to my radio. Flipping the switch will power on all the ground-side video gear (receiver and monitor), and simultaneously trip one of the servo channels on the KAP rig. On the KAP rig I’m installing a relay switch that will power on the video transmitter power when the switch on the ground radio is flipped. So flipping this single switch off will power off all the video gear on the ground and in the air. And flipping it on will power everything up.
  • I also picked up a boost power supply. It pegs at 9.5V, but I might swap it out for a 12V unit at some point. The idea is I can feed it 6V (or anything else between 1.5V and 9.5V) and it’ll output a nicely regulated 9.5Vdc. Add a line filter to get rid of the harmonics from the switching power supply on the boost board, and I can power my video gear off of the rig’s battery.
  • Finally, I ordered some reverse polarity SMA plugs with coax tails on them. I’m planning to make a 5.8GHz cloverleaf antenna for my video transmitter and a 5.8GHz skew planar wheel antenna for the video receiver. These are circularly polarized antennas, so they should reject a lot of the linearly polarized interference from other 5.8GHz devices. They also offer some modest gain, which should make for a stronger signal overall.

Yup, I’ve caught the bug. Now I just need a weekend with good weather and clean wind to fly in. Here’s hoping it’s the one that starts tomorrow!

– Tom

Posted in Electronics, Kite Aerial Photography, Photography, Radio | 1 Comment »

My HAM Shack

Posted by Tom Benedict on 16/01/2012

While trying to set up a video downlink on my kite aerial photography rig, I wound up studying for and getting my HAM license. I’ve set the video link aside for the moment, but I’m already studying for the General license and eyeing used HF gear on Ebay and with the local club.

Meanwhile I picked up a small dual-band handheld transceiver so I could start to play.

My HAM Shack - January 2012

It’s a Baofeng UV-3R Mark II with a Nagoya NA-666 antenna on it. (Antenna of the beast!)

I haven’t joined in a conversation yet, but I’ve been using it to listen to the local traffic and hear what I can hear. To a seasoned HAM this may sound odd, but keep in mind I’m a wallflower at parties. I tend to stand around until I find a place I can sit down and listen. Eventually I’ll socialize, and eventually I’ll even become outgoing. But beginnings are hard. It’ll take some time.

I’m still getting a feel for the layout of the local repeaters. There are some good lists, even some maps, but they don’t always jive. I programmed in a bunch of them, and spent some time just scanning through them. At one point I picked up a very clear conversation while driving from Kailua-Kona to Waimea. The UV-3R doesn’t let you store text names for stored memory channels, so all I knew was the frequency, not which one it was. I figured it was some repeater up on Hualalai, and that I’d lose it as I drove further from Kona. Instead it stayed clear the entire time! It wasn’t until I got home that I learned it was a repeater on Maui, the next island over in the chain, about 65 miles away.

For an inexpensive little radio, the UV-3R isn’t too bad!

Ok, to be fair there’s some stuff I wish I had on it. It doesn’t have a keypad or any way to generate DTMF tones. So no autopatch from the local repeater, and no controlling anything remotely. That’s fine. Right now I have nothing to control, and I do carry a cell phone. It also doesn’t have any way to limit the frequency range or the memory range during scanning. Also fine by me. There are only 21 repeaters in range, so it’s not a huge list. (Though after picking up that repeater on Maui, I think I need to expand my list!) It’s got dual watch, but no real dual listen. Not a huge deal, but it’d be nice.

One feature I really wish this radio had, and that I will look for in my next one, is to be able to listen to the avionics frequencies. In particular I’d like to be able to pick up the local tower traffic when I’m out flying my kites so I can tell if I’m causing problems for anyone.

And when the day comes that I do pick up a second radio, the UV-3R will make a nice backup. Meanwhile, it’s my entire station.

– Tom

Posted in Radio | 2 Comments »


Posted by Tom Benedict on 26/12/2011

I took the examination for a Technician class radio license on the 14th, and passed with only two wrong answers. Yaaaay! But until my name appeared in the FCC ULS database, nothing was official. I checked this morning, and there my name was. W00t! I have a call sign! WH6DWL  Or Whiskey Hotel 6 Delta Whiskey Lima. (Hey, can’t beat a call sign that means you get a double whiskey!)

So at long last I’m legal to power up the 5.8GHz video transmitter I bought over a month ago to use on my KAP rig. I’m also legal to purchase and use a UHF/VHF dual band radio. I hope to have the video transmitter working later this week. The HAM radio will have to wait a little while.

Meanwhile I’m studying for my General class license so I can play in HF space as well. (I wound up picking up the license manual from one of the VEs who administered the exam for my Technician class licensee before I even left the testing session!) After looking at the prices on HF gear, even used HF gear, it’s just as well the General class license will take me a while. I figure I’ll be licensed long before I can afford the toys.

I hope to make more HAM related posts to my blog in the future. Meanwhile I have a viewfinder to wire up, and call sign labels to attach to the transmitter!

– Tom

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Closer to a Viewfinder

Posted by Tom Benedict on 29/11/2011

I’m very very close to having a viewfinder for my KAP gear.


5.8GHz KAP Gear

The 5.8GHz gear arrived, and sure enough there was no FCC ID sticker on the transmitter. This just gave me more incentive to study for my radio license!

I also noticed the 900MHz gear I had built out also didn’t have an FCC ID sticker. So I can’t use it, either. Not until I have a license, anyway. Since the plan is to change over to 5.8GHz and since I can’t use the 900MHz gear anyway, I went ahead and pulled it out and boxed it up. While I’m waiting for the license exam, I plan to package the new gear and get it mounted to my transmitter.

The photo gives you a sense of scale for the stuff. It’s tiny! The video receiver is smaller than my monitor. If I can find all the right bits at Radio Shack, I’m considering mounting it to the back of the monitor, with all the cable connections housed in a little electronics enclosure next to it. This should keep everything neat and clean. Any time you use equipment in the field, “neat and clean” takes on more importance than just looking good. It means I’m less likely to snag something when I shove the radio into my bag. It means fewer sessions lost to disconnected cables or dirty connections. It means less chance of snagging my hand on a wire when I really do need to put the thing down and tend to the kite! “Neat and clean” is a good thing.

I’m excited about trying this out in the field. Even if I don’t wind up using it long term, it’s a good experiment.

– Tom

Posted in Electronics, Engineering, Kite Aerial Photography, Radio | Leave a Comment »

“Ya gettin’ deep, man!”

Posted by Tom Benedict on 23/11/2011

There’s a frame from one of my favorite comics as a kid, Snarf Quest, where the main character, Snarf, realizes he’s in way way over his head. There’s a great picture of him with hand to head saying, “Ya gettin’ deep, man!”

After I realized my 900MHz video system would never do what I wanted in the air, I bought a 5.8GHz 200mW system from Hobby King that would. All the reviews I read both on and off of the Hobby King website confirmed it really did have about a 1km range. Wow! Perfect! It’s almost too good to be true!

Sure ’nuff, it was. Questions came up in the KAP forums, and finally I was asked directly by a fellow KAPer: “Do you have a ham radio license?” Er… no.

To be fair, by the time that question was put to me directly, I’d already realized I couldn’t use this without a license and had already begun to remedy the situation. I ordered the ARRL Amateur Radio Handbook, found out who the local VEC is, found the local radio club, and talked to one of the members about getting licensed. I want to do this right!

And a good thing, too. Requiring a ham radio license in order to use high powered radio gear isn’t unreasonable. The whole point of the licensing system is to make sure the people using this gear know what they’re doing and will act responsibly with it. No bad thing! But even better, the studying necessary to pass the licensing exam has answered soooo many questions I’ve had about radio, I’m asking myself why I didn’t do this sooner! Radio direction finding for locating a stratospheric balloon package? Answered. How to get telemetry from a balloon payload? Answered. How to do video from a KAP rig? Answered. What bands can I use inside the US? Answered. Can I hand my gear to another KAPer to use while I’m there? Answered. Can I give someone else my gear to take home with them and use, knowing they don’t have a license? Yeah, answered. Sometimes Google is your friend. Sometimes it helps to have all the information packed into one extremely dense book that you can read cover-to-cover. This is one where the book wins.

At the same time, though, I do find myself with head in hands thinking, “Ya gettin’ deep, man!” Back when I was an undergraduate, as we were filing out of the final exam for our Stellar Atmospheres course, one of my classmates turned to me and said, “I just wanted to look through a freaking telescope, man!” Amen, brotha. I just wanted to see what my camera was seeing when it’s on the kite.

But I can’t complain. Knowledge is like candy. It tastes great, but it can be overwhelming when you try to swallow too much. It’s an utter high when you’re sucking it down, and the crash at the end can be a killer. Occasionally you get some gawdawful bit like an orange strawberry nougat, but most of it is pretty darned sweet. Reading about radio technology? Pretty darned sweet if you ask me. One more week and I think I’ll be ready to take the exam.

– Tom

Posted in Radio | 2 Comments »