Video KAP for Licensed Hams

Dennis Foster, Commerce, Oklahoma, USA       June 7, 2002

Ham ATV Tx with Camera and Battery [Ed- Below are excerpts of 3 emails from Dennis Foster. The video transmitter that Dennis uses is the MFJ-8704 Micro ATV Transmitter from MFJ Enterprises. It operates at 433.97 MHz with 50-100 mW of power. A Ham Radio License is required to use the transmitter. I am not sure of the make of the video camera that Dennis is using. Dennis' old email address no longer works so I hope that he will see this article and give us an update and fill in some of the gaps. ]

August 11, 2001
I got my new little ATV transmitter today and tested it out at work tonight. I must say I am very pleased with it all. I used a simple antenna made from a wire 6.75 inches long [17.15cm] and found the range to be very good!

I have attached a photo of the complete system, tiny camera and all. It all will operate off a 9 volt battery. The camera will run in excess of 8 hours on one battery. Haven't figured the current drain on the transmitter yet but it will probably go much longer than the average flight would last.

If the wind blows here tomorrow, I will fly and test it all out. I get an excellent picture just using a cheap 5 inch TV with the slide rule type tuning. The signal is just below channel 14 on UHF! The paperwork with the transmitter states 1/2 mile range with simple antennas, up to 8 miles with yagi type antennas! There should be no need for high gain antennas as I see it now! ha!

September 2, 2001
I have completed some testing of the little video system and I have problems to resolve with it. Most, if not all, I probably created myself by the type equipment I am using for KAP.

First of all, the ATV transmitter works perfect and the range is really unknown from the kite as the signal is much stronger than needed to provide noise free pictures at the receiving end. TV signals are an amplitude modulated type signal, i.e., AM and the R/C equipment I am using at the present time, is also AM instead of FM! This presented some problems with the KAP rig going bonkers when it was all turned on due to intermodulation problems of the TV signal getting into the R/C receiver. The oscillator in the little camera caused as many, if not more, problems as the ATV transmitter. I resolved all that by rearranging and shortening the leads and also by installing ferrite cores on all leads, wrapping the leads around the cores to stop the travel of RF on the wire. Once that was resolved, I noticed that the R/C transmitter itself would cause interference on the little TV I was using to monitor the video!

What I finally ended up doing for the time being was to turn the camera till I was aimed where I wanted, I then turned the [RC] transmitter off, and took a good look at what the camera was looking at and went from there. I think going to a modern FM rig will eliminate 100% of these man-made problems and will know for sure as soon as I get the new equipment in from Tower Hobbies. I will let you know the results of that then.

The other problem that I didn't anticipate was the sensitivity of the little camera! It was complete overdriven by outside, ambient light. It is of course a very good low light camera but that is not what I was wanting. I have resolved this by remembering that, all camcorders have the same problem and get around this by using internal filtering. I had an old camera that I bought at a thrift store for $1.91, to rob the viewfinder out of. I took it apart and sure enough, there were two filters in front of the Vidicon imager. One seemed to do nothing in front of the camera and the other one solved the over-driving of the imager. I have yet to try it since the "fix" but if the winds hold today, I will fly just the video and see how it looks.

My complete KAP rig with video and batteries, complete, weighs in and 1lb and 13.9 ounces [822g]. That is using two 9 volt batteries, one each for the camera and transmitter. I can run both of them off one battery and save some more weight if needed. I have also discovered that it would be much more convenient to package all this video stuff in a container of its own and attach it below the rig so it can be removed easily and not always on there as there might be times when I wouldn't want or need to use it, therefore eliminating the extra baggage! I plan on doing this before I do much more flying with it.

Back to the camera, the problem is that it is overdriven by it's extreme sensitivity to the infrared spectrum of light. The filter needed is one that will block, or , restrict infrared from entering the lens. This can be tested by holding the filter in front of the camera, watching your monitor and then, taking a TV remote control, aiming it at the camera and looking for the blinking of the light in the monitor! I am not sure that the filter I used is the best one as the imager in the old camera was a Vidicon, not a CCD (charged coupled device) which is probably more sensitive. It works though and will let me continue with the experiments. If you would like, When I finish all the tests, using the FM system, filter, etc. I'll write a short article listing all the parts, pieces etc. problems encountered and what to do to make it all work properly!

Later On September 2, 2001
Well, after much frustration I got the camera airborne today. The winds are the pits here most of the time to make the Flowform 16 useful! I will save it for the hurricane/tornado seasons when the wind is adequate! ha! I finally took the camera equipment off the rig to lighten the load, and, attached it with tape and rubber bands about 100 feet down the line from the kite. The filter seems to have done a nice job in preventing the camera from washing out. It is very bright outside today which is a good test for it. The monitor was hard to see unless I put it inside my little truck in the shade but the picture was great!