Enhancing portable SSTV
By Del Radant, N6JZE
With the advent of the Kenwood VC H1, Visual Communicator
unit, there's been much interest in Slow Scan TV. It is now possible to
show the NCS of a Public Service event existing conditions at a portion
of an activity where additional assistance may be needed.
There was recent discussion in the San Diego section about
the possibility of supporting the American Red Cross and the California
Department of Forestry with some visual records of the extent of any destruction
during any emergency.
To prepare for this evolution, several local Amateur Radio operators purchased
the Kenwood VC H1 SlowScan Visual Communicator and the Kenwood THG71A
Dual Band Transceiver.
We demonstrated the capability of these units by showing
the various members of our local clubs what was possible using this combination.
Some of the pictures were not as clearly defined as we would have liked.
So a project was instituted to enhance the picture quality by adding a
digital source separate from the reproduction device furnished on the
VC H1. By adding a digital source with high pixel capability, we did achieve
the desireûd detail in the pictures. Here's how we accomplished
our goal of enhancing the video picture.
The digital source
The major restriction in the choice of a digital camera,
is that the camera must have a video output jack. This is necessary for
the transfer of the picture to the VC H1, to store it there and, at a
later time, send it to the distant receiving office. Most of the later
model camcorders, have a "video out" capability, so one may
view the picture from the camera on a TV screen.
The choice of the digital camera, is of one that has a
"VIDEO OUT" port. Most of the better models are so equipped.
Digital cameras hold numerous pictures, while a camcorder normally has
only one still frame available from the recorded tape (a DVD camcorder
can provide a number of pictures from the special DVD tape).
Mount construction
The combination of these devices required a supporting device
that was able to accommodate all three items and still be portable and
could be mounted on a tripod. This was accomplished by constructing an
aluminum and copper mount to hold each unit, provide convenient access
to the controls, and also offer application of power from an outside source.
I constructed several mounts for various sizes of cameras and camcorders.
Copper was chosen for the construction of supports for the
Kenwood units because it's easy to bend and shape for each item. The base
support was made from heat-treated aluminum.
The copper mounts are made from 22 gauge material. Ordinary
tin snips will cut this material quite easily. (I suggest that a trial
form be made of heavy card stock, fit it around your units and see if
it satisfies the needs, then transfer these dimensions to the copper stock.)
The basic dimensions are 5 1/4 X 2 1/4" for the transceiver and 5
1/2 X 2 1/4" for the VC H1 unit.
All the bending and forming was done using a bench vise
with a 3" jaw. A hand-operated electric drill was used to drill the
small mounting holes. A floor-mounted drill press was used to drill the
larger holes for the VC H1 plug hole in the flat aluminum stock.
The base material used is heat-treated aluminum, specifically
chosen for its rigidity. It can be flat or angle shaped, whichever is
most readily available. The dimensions are 2 1/2 X 12". The opening
for the cable plug can be made by drilling four adjacent 1/2" holes
in the chosen position and filing away the excess material. An electric
scroll saw with the proper fine tooth blade may also be used to make this
hole.
Some care must be taken when drilling the hole for the
power plug for each unit. A very small drill be used to place the hole
directly over the pin in the unit (you can see this pin through the small
drill hole). Then enlarge it 3/8" for the power plug.
Adjustments can be made to accomodate the available camera
and transceiver. The mount for the VC H1 is standard and the hole in the
base is required. Sizes of the support can be adjusted. A single slot
to admit the plug to enter from the bottom causes the transceiver to be
raised upward, hence a modification would be needed in the copper mount
construction. The hole for the insertion of the external power cable must
be made for the chosen mounting location of the unit.
The dimensions furnished for the copper stock are for a
Kenwood THG71A unit, and the Kenwood VC H1. Use a file to remove the small
molding nibs, on each side of the Ni-Cad battery case of the Kenwood TH
G71A. They prevent the unit from sliding smoothly into the support.
Other handitalkies work as well, but you must make an adapter
to plug into your chosen transceiver to feed the audio and keying circuits.
The cable for the THG71A is furnished in the package of the VC H1, and
plugs into the Kenwood transceiver (it's much easier to use the Kenwood
unit).
The short cable from the video output jack of the camera,
to the socket of the VC H1 is also a home-brew cable. When using the digital
camera, the viewing head piece on the VC H1 is removed, and the cable
plug, takes its place. The plugs and angle adapters are available from
RadioShack. Follow the detailed instructions when constructing this cable.
The plugs and adapter are tipringsleeve (TRS) devices. (Note plug size
and type, on plugin lens unit.) Ordinary audio plugs WILL NOT work, as
one uses the tip and the opposite end uses the ring. The "video out"
plug for the camera is also a tipringsleeve unit.
We also substituted nickel metal hydride (NiMH) batteries
for the furnished alkaline batteries. RadioShack has these batteries and
a spare set is now kept for the VC H1. When battery operated, it consumes
considerable current. The furnished AC Power pack is rated at 2500 MA
@ 6 volts. Charger devices for NiMH are available.
My Olympus C3030 Zoom camera uses NiMH batteries also and
it too operates on 6 volts. A home brew cable is required for each 6 volt
unit, that brings the current from a double 6 volt gel cell battery. It
is charged as a 12 volt unit but it provides power, as two separate 6
volt power sources. One cable for the camera, and one for the VC H1.
The THG71A transceiver has a Ni-Cad battery, and a additional
fully charged unit is on hand. A Kenwood PG 3J power cable may be used
if operating near an automobile, or from a deep cycle battery. With 12
volt power, they transceiver developes 5+ watts output. (DO NOT use a
Kenwood PG 3J cigarette lighter cable, as a power source for the VC H1,
as it requires 6 volt DC power.)
One of the members uses this setup with a Sony camcorder
and an Alinco Dual Band Transceiver. The picture definition with a high
pixel count camera, produces a much better photo.
Another member also uses an Olympus C3030 Zoom camera, but
chose to keep his camera in hand, so an appropriate cable was constructed,
to reach the tripod mounted VC H1 and Kenwood transceiver. You can take
many picturesg, and then transfer up to ten pictures to the storage in
the VC H1 unit for later transmission. This action frees space for other
exposures on the camera's memory chip.
The cable for the video from the camera to the VC H1 is
made from microphone cable. (Follow the drawing for the correct length
and connections, using extreme care not to fill the internal lugs with
excess solder). If thse system does not function correctly try reversing
the cable. The end for the VC H1 is using the RING, and my camera uses
the TIP. I color code the VC H1 end with red shrink tubing.
Follow the instructions in the booklets that come with
each unit. Set up an operation with your friends and practice in the operation
of all the controls. Be ready for any emergency within your area. You
can also take pictures with the digital camera and, at a later date, display
the information at a club or public event.
Software considerations
There is a Kenwood program, KCT24S, that permits a remote
unit to receive and transfer your pictures to a computer for processing
and printing. Windows 98 is required to use it.
Additional accessories are available for many cameras,
that permit the transfer of the snapshots into your own computer for printing
out the phtographs in color. Adobe PhotoShop 5.0 LE was furnished with
the Olympus Camera. Other photo processing programs are included within
Windows 98, and some programs are furnished with Hewlett Packard products.
A cable is furnished with the Olympus C3030 camera package
to view the pictures on the Smart Card in the camera on a color TV. This
feature allows you see your work and allows you to experiment with exposures
and additional features to improve your skills.
It has been a real pleasure to send photos on any VHF/UHF
repeater operation or any amateur frequency using Slow Scan TV. Join in
and share the fun!.
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