RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
Wax nostalgic about and learn from the history of early electronics. See articles
from Popular Electronics,
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Ironically, an RF Cafe visitor just within the last couple days
wrote about possibly getting his Amateur radio license in order
to permit live broadcasting of his kite-borne video camera system
(known as "Kite Aerial Video" [KAV]),
or Kite Aerial Photography [KAP]). Slow scan television SSTV
has long been a popular facet of Ham radio since prior to broadband
Internet connections; it was the only practical method available.
Older equipment was large, heavy, power hungry, and relatively
expensive, but today you can buy a much improved camera for
a few bucks that transmits real-time via an unlicensed 2.4 GHz
wireless link. That data stream can be recorded for later use
of streamed real-time to the Internet. As with so many other
things, easy availability takes some of the challenge out of
it, but the world benefits from having all kinds of way-cool
videos to watch!
Hams Go Video
Amateur TV - an exciting new hobby
By Art Zuckerman
One day, in the not-too-distant future, the average ham may
mean it literally when he asks a distant buddy, "How do you
He will mean not "How well do you hear me?" but rather "How
clearly can you read my test pattern?"
Ham TV today is admittedly a limited pastime, indulged in
by a handful of dedicated adventurers using makeshift equipment.
But at least one electronics manufacturer, the Electron Corporation
of Dallas, Texas, is determined that things will not always
be thus. Mort Zimmerman, the company's president, reasoned that
when the Federal Communications Commission set aside the 420-450
mc. band for amateur television back in 1957, it meant for the
band to be used. So he is marketing a complete ham video station.
Dave Baxter of Dallas, known in amateur circles as W5KPZ,
is using the new equipment to telecast to several other Dallas
amateurs whose TV sets are equipped with special u.h.f. converters
to receive him. And in Denver, two ham clubs are buying the
Electron Corp. gear on time, paying for it with a $6 monthly
membership assessment. The cost of the complete package at present
TV ham Dave Baxter, W5KPZ.TV, is sandwiched
between his gear. Dave works out of Dallas, Texas.
Ham TV Pioneers. Though such commercial
gear should do much to popularize ham TV, amateur television
has been with us longer than you might think. Its roots can
be traced to the earliest days of video experimentation. And
just before World War II, the Radio Corporation of America actively
encouraged amateurs to jump on the television bandwagon it was
then striving to get on the road. With the war, television went
into mothballs for five years. But when it ended, the Armed
Forces unloaded tons of surplus radar and other electronic gear.
Sophisticated version of flying spot scanner.
Older system involves putting transparency directly against
screen of TV set with raster reduced to size of transparency.
Some of the Armed Forces' surplus gear was snapped up quickly
by a few of the more enterprising radio amateurs. Many of these
hams were operating on the West Coast, where probably the greatest
concentration of video hobbyists can be found today. On clear,
bright days, small groups of these intrepid pioneers can be
seen climbing up neighboring mountains, loaded down with equipment
with which to exchange test patterns and live images.
For transmitters these hardy hams generally use modified
radar gear, though some build their own. The pickup equipment
is likely to be a primitive iconoscope camera originally built
for wartime guided bombs, a Buck Rogers type weapon tried by
the Army Air Forces toward the close of World War II.
Unfortunately, these surplus iconoscope cameras provide considerably
less than good picture quality, and they gobble up light much
too greedily. So the average member of the tiny TV ham fraternity
is more likely to content himself with transmitting slide shows.
For this he uses a setup known as a flying spot scanner.
Flying Spot Scanner. This interesting device
is actually made up of two separate items: . an ordinary TV
receiver and a photoelectric multiplier tube, such as the 931A.
Together with a video amplifier and a video transmitter, the
flying spot scanner makes a dandy gadget for televising still
transparencies. Here's how it operates.
The TV set is tuned to an unused channel, so that its screen
is lit up with the swept trace lines but shows no picture. Its
brightness control is turned up as far as possible. Next, a
slide or other transparency is placed against the face of the
picture tube, and the set is adjusted until the trace lines
just fill the part of the tube covered by the slide.
Now the photoelectric multiplier is placed right in front
of the slide. The light hitting the photocell, after going through
the transparency, is not just a blob of illumination; it is
actually the scanning action of the picture tube's electron
gun. As this light hits the photoelectric tube, it generates
a signal that is fed to the video amplifier. The video amplifier,
in turn, feeds either a monitor set, a video transmitter, or
Result: a neat reproduction of the transparency on the monitor
and on the receiving set of another ham.
This technique can also be used to produce positive images
with photographic negatives if their phase is reversed in the
Tuning up the transmitter.
Dave Baxter's station is believed to be the first installation
of commercially made (Electron Corp.) ham TV gear.
Two Typical TV Hams. Many of today's television
amateurs, as might be expected, are actually professional electronics
engineers who like to tinker with video in their spare time.
In New York, for example, two TV hams are Arnold Proner, W2OMU,
a television broadcast engineer with the National Broadcasting
Company. and Bill Ziner, W2MMY, an engineer in the research
department of the Lewyt Corpora-tion.
Working together, Arnie and Bill actually built their own
vidicon cameras and amplifier-transmitter gear from the ground
up, copying standard circuits in commercial use. The cameras
are patterned after an old RCA vidicon design used for televising
motion picture films.
For optics, Arnie Proner uses an f/1.9 50-mm. lens
from a Leica camera. "It gives a slightly telephoto effect on
the vidicon," he will tell you, "but it does a pretty good job."
Before Bill Ziner graduated to the vidicon, he had worked
out a really sweet version of the flying spot scanner. "I took
an old 35-mm. projector and rewired it, replacing the lamp with
a photoelectric multiplier tube," he relates. "So I had a perfect
slide changer setup for my transparencies. Then I simply filled
my entire TV picture tube with scanning lines and focused the
slide projector on its face. I worked out the focus by the focal
length of the projector's lens and checked it on the monitor.
Airing slides with this rig was just like putting on a regular
slide projection show, only the process was reversed."
Home-built rig of Arnold Proner, broadcast
engineer for NBC, includes rack-mounted amplifier-transmitter,
vidicon camera, and monitor. Most of the equipment is similar
to early commercial circuitry.
Vidicon Simplifies Matters. The vidicon
cameras turned the flying spot scanner into a child's toy for
Bill and Arnie. They still sent each other test patterns and
other slides in transparency form, but now they were also sending
live pickups with ease. And transmitting slides was a much easier
They did it in two ways. Either they projected the slide
on a wall and turned the vidicon camera on the projection or
they aimed a slide projector right into the vidicon camera's
lens. This would give a reverse image which was then corrected
by electronic flopping in the amplifier.
Arnie also succeeded in transmitting movies. He did this
by beaming an 8-mm. projector on a screen made of translucent
material and spotting the vidicon behind the screen. The vidicon
picked up a reverse image from the rear of the screen, and the
image was electronically flopped.
Because their gear was not fully refined, Arnie and Bill
found that they had to take turns transmitting to one another
on video. Their transmitters completely blanked out their own
receivers. But this was normal radio practice and presented
Arnie's gear once was put to a very practical use when he
and his wife couldn't corral a baby-sitter while they made a
short visit next door. Arnie trained the vidicon on his sleeping
infant and Bill did the baby-sitting electronically at a distance
of ten miles.
Rack-mounted ham TV transmitter manufactured
by Electron Corporation is small enough to sit atop a desk.
Use of slides permits the equipment to be adjusted and serviced
Commercial Equipment. Ham television is
characteristically a strictly video proposition; because hams
have radio transmitters and receivers anyway, there is no need
for TV audio circuitry. And amateur TV, as practiced by these
pioneers, is primarily a builder's hobby. There are few other
video hams within reach of their short-range equipment, and
the challenge is mainly one of seeing if they can put together
However, the Electron Corporation, a subsidiary of Ling Electronics,
Inc., hopes to change all that. Its new equipment is ready assembled,
specially designed for operation on the 420-450 mc. amateur
Field tests by the company indicate that this equipment provides
excellent reception at a distance of 18 miles. The possibilities
of relay transmission are being explored too. With a relay system,
a string of hams spaced 18 miles apart could establish a network
to cover real distance.
Electron Corp. officials are talking about the use of their
equipment to bring amateur collegiate radio into the television
picture as a non-commercial educational service. Another possibility
they envision - and one linked with their hopes for college
TV - is the purchase of converters and special antennas by the
general public for looking in on ham television.
The u.h.f. converter, incidentally, is price-tagged at $79.50,
and the receiving antenna for it costs $12.50.
Television may eventually become an important adjunct to
the ham in his traditional emergency service role. Visual coverage
of disasters could prove valuable in coordinating civil defense
activities by adding "eyes" to the "ears" of emergency radio
Kite Aerial Video
Posted May 11, 2015
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