ATV Hard Hat Cam

ATV Hard Hat Cam
P. C. Electronics 2522 Paxson Lane Arcadia CA 91007-8537 USA
Tel: 1-626-447-4565 m-th 8am-5:30pm pst (UTC - 8) Tom (W6ORG) & Mary Ann (WB6YSS)
Web site: http://www.hamtv.com
©2011
Email: ATVinfo @ hamtv.com
ATV Hard Hat Cam
There are many emergency service applications where the on site commanders must
remain in an emergency operations vehicle but would love to see what others are seeing.
This is especially true when decisions must be made quickly and cannot wait for a voice
description or interpretation. The Hard Hat Cam is ideal for transmitting to a portable
repeater back to an emergency operations center. A picture is worth a thousand words.
Videolynx
434
This application note describes how to build into a hard hat a 50-100 milliwatt 434 MHz battery
operated ATV transmitter and color camera. Snow free line of sight DX from the hard hat to a 8 dBd omni
or 5 element beam is about 1/2 mile. Both the Videolynx ATV transmitter and CG-35a mini color camera
are powered by two 9V alkaline batteries in parallel which can give over 10 hours of continuous operation.
One should note, however, that drilling any holes in an approved hard hat cancels the OSHA certification,
and reduces the amount of impact protection if you will be using it in a dangerous area. An alternative
would be to package the transmitter in an aluminum box and clip it to the hard hat.
I purchased a plastic hard hat at Home Depot because I could not find a metal one. Metal would make
a much better ground plane, but instead, I glued two 1.5x13 inch strips of aluminum foil in the shape of an
X inside the plastic hard hat after drilling.
A 3/8 diameter hole is drilled in the top center for the antenna UG-1094 BNC chassis connector.
Solder the coax braid directly to the top of the BNC shell. Next drill 1/8” diameter holes for the 9 Volt
battery holders with one 3” to the rear of the BNC and the other 2” to the front. I
used 4-40x3/8 screws with the nut and lock washer on the outside of the hard hat
to mount the battery holders. 1/16” holes are drilled for the slide switch
approximately 1.5” forward and to one side from the BNC.
Drilling for the CG35a mini color camera is a little more involved. A hole
must be drilled in both the camera bracket and hat with a .312 dia. drill so that the
cable plug can be fed through from inside the hat. Drill 1/8” holes for the two
camera bracket mounting holes, mount the bracket using two 4-40x3/8 screws,
lock washers and nuts, then drill out the bracket and hat thus insuring good
alignment of the holes. Remove the bracket. Remove the connectors on the
camera cable.
Next, cut two 1.5x13” strips of aluminum foil and glue to the hat inside and
centered on the antenna jack hole. Let it completely dry then cut the holes free
with an Exact-O knife.
Make a 1” wide sheet aluminum or brass bracket for the Videolynx transmitter
by first drilling a 3/8” diameter hole centered and 1/2” from one end. Make a
right angle bend 1” from the drilled end. Loosely mount the bracket on the BNC
jack. Then place the Videolynx against the bracket with the leads pointing toward
the BNC and bend the metal tight around the transmitter module.
Mount the power slide switch, battery holders, and camera. Connect the camera
red power cable and Videolynx power leads to each side of the dpdt slide switch
on one end. Connect both of the 9V battery clip leads (3 if using the Z70A
transmitter) to the respective center lugs - red +9 V on one side, black or ground
on the other. Rather than splice the yellow video coax I put a RCA plug on the
cable and plugged into the Videolynx video jack. The line audio cable is only
used with the Z70A transmitter. Use a good resonant 50 Ohm antenna plugged
into the BNC jack such as the Diamond RH519 available from us. You can also
take the hard hat off and plug in a small beam like the OAL 5L-70cm to more
than double the distance for fixed portable applications.
BNC jack(s) - UG-1094, www.mpja.com
Parts list and sources:
RCA Plug(s) - Radio Shack 274-339
Videolynx 434 transmitter - P. C. Electronics $99 or
DPDT slide switch -Radio Shack 275-403
Videolynx Z70A transmitter with sound - P. C. Electronics $149
W6ORG
9V battery clips - Radio Shack 270-324
CG-35a mini color camera - P. C. Electronics $89
©8/2011
9V battery holders - Radio Shack 270-326
Diamond RH519 whip antenna - Your favorite ham store
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