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Joe · January 5th 07, 02:46 AM posted to rec.radio.amateur.homebrew

wrote:
Joe wrote:
Hi Folks,

I just found this group. Not sure if this is the right place to ask,
but here goes:

I am presently a student studying for my MSc in Applied Physics. Next
semester I have a course in Electronics which is going to require me to
do a project. Now I have worked with radio control vehicles before
(ROV's), but this time, I wanted to build a vehicle and have it be semi
autonomous, ie with a microcontroller. Along with that, I will need a
fairly long range (say, 1 mile) video transmitter to put "eyes" on the
vehicle. I have worked with the short range, commercially available
wireless video cameras that use the pinhole camera and have a range of
about 300 feet unobstructed. I was wondering if anyone on this forum
knows of a kit that I could purchase to build one myself (I may be
mistaken, but an assembled unit probably costs a lot more). If this is
not the right forum, pls let me know that too. Links, ideas, etc are
welcomed.

TIA,

Joe
KB1KVI
(kilo bravo1 kilo victor India)

Joe,

Before suggesting anything it would be helpful to know a little bit
more about the requirements. Are you considering analog or digital TV
transmission? What frame rate is required? How many horizontal lines?
B/W or color? Are you planning on using amateur radio or unlicensed
frequency bands? How long are the transmissions? Any size/weight
constraints?

There are many tradeoffs to be considered. For example if you are
sending digital pictures, the frame rate, vertical and horizontal
resolution, and color depth will dictate the data rate in bits/second.
Based on a given data rate there will now be tradeoffs in terms of
frequency band, power, bandwidth, SNR, antenna size, power supply
requirements etc.

We also need to know if you are considering building something at the
component level or whether you are trying to use off-the-shelf modules.

Sounds like a fun project - Roger

Hello Roger,

Whew! Well, I am glad you asked. I would like to use the KISS
principle, if you know what I mean. I will try to answer in the order
you asked: Analog TV, actually, I would like to use my own TV, like
maybe cable channel 59 (I know we have some video bandwidth around
there, 70cm) at least for the initial close to home testing. However,
there is a possibility (remember, this is still a work in progress)
that I will want to monitor the video from my vehicle in a field type
test situation, in which case I have a couple of smaller color monitors
that run on 12V and use RCA phone jacks, so I would need a receiver box
to plug into the monitor. Definitely color TV and I thought that ,
given the range requirement of about a mile, I would need to use the
amateur band. If not, that's fine too. Length of transmissions, now I
hadn't thought about that one. I was planning on sending him on his
way, as I said, semi autonomously (with a microcontroller taking care
of all the things like not bumping into anything, going off cliffs, or
ending up in the drink), and then send a command (possibly DTMF thru
walkie talkie) to switch on the video and start monitoring where he
(well, it) was located and what he was seeing. The size, weight and
power constraints: It is to be an all terrain type vehicle, right now I
am planning on using a steel platform (actually, one of those radio
flyer wagons) which weighs about 10 lbs unloaded. I would estimate that
after adding the motors and wheels (big wheels, like maybe 12-14 inch
diameter), 12V deep cycle battery (about another 40 to 60 lbs), I may
be able to accomodate another 5 lbs or so for the camera, and
transmitter, and possibly another separate power supply (battery) for
the camera since I will be using a 6V (4.5AH) battery to power the
microcontroller and associated electronics, sensors and whatnot. I
would rather have the 12V battery powering the DC motors that will be
propelling him forward (they will probably be pulling 3-5 Amps each).
So there will also probably be inductive 'noise' from the motors as
well, but I believe I can shield most of that, if necessary. I always
prefer to use off the shelf items, but I can do some soldering and
putting kits together also. I guess to summarize, it is very flexible
in this stage, as I haven't gotten the motors or wheels together yet, I
am still planning all this and trying to cover all my bases so that I
can have something working possibly by the early summer when semester
ends. I have done this before, but on a much smaller scale and limited
only to ROV's using off the shelf radio control non amateur band. I
realize there will have to be tradeoffs, e.g., I may have to go with
black and white instead of color, I may not need a mile range for the
video transmission,etc. I think TV resolution is 480 lines. That would
be ideal. I guess I am wondering what is out there for me to choose
from and then tailor make this part of the project based on my budget
and what is available. Also, I may not necessarily be line of sight
when I will be needing the video (in a field test situation). I really
don't know about transmission times.

Oh yes, it's going to be fun..It already is :--]]]

Joe
KB1KVI
(kilo bravo1 kilo victor India)