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 tying 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 read me?"
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
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 is $2895.
TV ham Dave Baxter, W5KPZ.TV, is sandwiched between his gear.
Dave works out of Dallas, Texas.
Sophisticated version of flying spot scanner. Older system involves
putting transparency directly against screen of TV set with raster reduced to size
Tuning up the transmitter. Dave Baxter's station is believed
to be the first installation of commercially made (Electron Corp.) ham TV gear.
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.
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 both.
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 video amplifier.
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.
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 easily.
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 Corporation.
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."
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 project.
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.
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 workable rigs.
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 television band.
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 communications.
Kite Aerial Video
Posted February 2, 2022 (updated from original post on 5/11/2015)
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