While researching video systems for a recent project, I stumbled across something I had completely forgotten about Amateur TV systems.

Amateur TV is limited to those who hold a Technician Class or higher amateur radio license.  If you don't have a license yet, I highly recommend getting one.  ATV comes in several different frequencies; 70cm (420-450 MHz), 33cm (902-928 MHz), 23cm (1240-1300 MHz), and 13cm (2390-2450 MHz).  This gives you a wide range of frequencies to choose from to avoid RF interference.

I used the 434 ATV transmitter from www.hamtv.com, which runs about 99$.  This can be received on any TV that can receive analog cable signals via channel 59.  My receiving system consisted of a 5-element Yagi antenna tuned to 434Mhz connected to an old VCR outputting to a small LCD monitor (the older VCR had better reception than a newer hybrid TV).  I tried to use a USB TV Tuner at first, but I could not get a signal unless the transmitter was very close (they have very weak pre-amplifiers) and there was a buffering delay of about 2-3 seconds.  Not good for FPV.

My range for the 100mW system ended up to be approximately 2500 feet.  Next time I will get the 5 Watt version for another $100 that will give me much more range and will allow me to drop the VCR from the setup and just use a cheap portable LCD TV.  Maybe if I am really ambitious, I will even pump the power to 20 watts with an amp.

Overall I was pleased with the system I had slapped together on a tight budget.  The transmitter module was easy to use and, thanks to the circuitry being potted, even survived a 70 mph crash into the desert floor.

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Lately, I've been interested in using 802.11 (WiFi) for command and telemetry links. When we flew at the AUVSI competition, our XBee link faded on us. While this was primarily an antenna problem (the ground station was looking at the end of the XBee's 1/4 wave whip), the restrictions on ISM band devices make these kinds of problems really hard to fix. I think Ham WiFi link would be more reliable and easier to deal with.
Is aeronautical mobile permitted on ATV??

Guess it is looking at this

http://www.eham.net/articles/10144
Each audio channel has a max speed of 2400 baud maybe 4800 and may drop some data from noise hits.
As you see, yes, it's permitted. Radio control is also permitted (generally in the 50 MHz allocation for that), and there's precedent for doing command and telemetry links with AMSAT. I'm not sure how these precedents might apply to UAV's yet, but unencrypted 802.11 is certainly permitted for mobile, so I'm sure something can be worked out. The key issue is that generally Ham transmissions can't be in a private format or encrypted.
I found this....
http://www.flytron.com/simpleosd.htm
It uses the audio ch. of the TV signal.
You could use anything that transmits audio as long as you have a receiver to convert back to audio.
Then use the PC display.
The bonas is the OSD !
Earl
WOW!

Glad I found you guys.
I am tooling up to run a 440 tlm/video downlink.
Do you think I can push at least 2400 baud through a TV sub-carrier?

John
Wonder if anyone has hardware and/or software up and running and/or would just like to share ideas?

My RC up link is 72 MHz …current model
Pitch and yaw on right stick…current model
Throttle on CH6 knob…current model
Pan & tilt on left stick… prior model

CH5 three position switch Adrupilot 2.6 mode control…on test bed, GPS lock and all servos move in correct direction.

Video TX is Z70A (HAMTV.com)…not powered up yet
ATMega328 Ground station…kit built, not powered up yet
74HC4046 Telemetry modem…Up and running at 9600 baud but probably way to fast for the Z70A audio channel.

Wayne,
I am new to this forum and so glad I found your thread and certainly don’t want to step on toes or hijack a thread and don’t know if this is the place to share a couple free ‘two-thumbs-up’ test equipment downloads. One, a soundcard oscilloscope / spectrum analyzer / signal generator, the other a USB stand alone dot-exe file (no dills) smart terminal with RX, TX, file storage, baud rates out the kazoo, more…Plays real nice with ArduPilot.

John
Hi John, like Kip sez to Uncle Rico about time travel, 'Easy'! Flytron has a 4 page developer's manual detailing ASK (audio shift keying). The TV audio subcarrier has a bandwidth of 125 KHz. -KI6OYR-
Nate, good luck on your test! One word of warning, there are a couple of tests in the FCC's repertoire that are weighted heavily in the regulations area (i.e. rote memory) so don't take it for granted that it'll be a pushover. I passed the commercial exam and don't think I could have just walked in to the amateur exam and passed without going to a 2-day seminar given by the Navy Post Graduate School Ham Club in Monterey. -KI6OYR-
Hi Wayne, you brought up a very interesting idea re: your previous ham TV repeaters. Ham UAS/V'ers could take advantage of existing or new repeaters for video telemetry AND control uplink purposes and totally get rid of the current hi power requirements for long distances! I can't handle that VUVU noise either after listening to jet turbine whine all day!
KI6OYR,

Thanks for the advice! I've got a good "Elmer" to help me when I get stuck.The ARRL License Manual is very good, nice short topics, easy to digest,and if you don't quite understand something you don't have to read through 100 pages to find the answer! Anyway I'll be sure to spend extra time on the FCC regs!!

Nathaniel
Hi Mike, ARRL has a heap of frequency and emission guidelines that organize the bands (which is a good thing) and of course band edge constraints and allowed modulation methods but the whole idea of amateur radio is to encourage experimentation and 'DIY'! I have some ham buddies that are actually afraid to tweak their own equipment for fear of committing an FCC violation. My point here is to not discourage anyone interested in getting a ham license because of a perceived regulatory quagmire.

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