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KLM, a big name in ham radio antennas, has joined the satellite game with several complete systems. Their automated tracking system a//ows you to turn your dish from bird to bird from the comfort of your living room.

W hile the experts debate the relative merits ot spherical antennas like the one shown here, hobbyists are finding new and simpler ways to build this inexpensive "8-ball" design.

KLM, a big name in ham radio antennas, has joined the satellite game with several complete systems. Their automated tracking system a//ows you to turn your dish from bird to bird from the comfort of your living room.

W hile the experts debate the relative merits ot spherical antennas like the one shown here, hobbyists are finding new and simpler ways to build this inexpensive "8-ball" design.

16 73 Magazine * November, 1981

Reador Service for tacfng pagp W4 -

Heathkit

HeamKit

Space Spinoffs for Amateur Radio the makings of a communications revolution

Partus C Barlow WA1DCP Downlink inc. 30 Park Street Putnam Cl 06260

Wes Thomas W2IKQ 606 Fifth Avenue East Northport NY 11731

Revolutionary changes in amateur radio may be on the way With the cost of backyard TVRO (television receive only) systems plummeting and the telecommunications indus try gearing up for rooftop data and video business communications, new forms of space-age amateur radio communications are becoming feasible Here are some of the mind-boggling possibilities:

• National or global two-way amateur satellite communications, 24 hours a day.

• Dramatically improved moonbounce communications, using low-cost TVRO dish antennas at microwave frequencies

• And national packet-switched microwave-linked repeater networks for voice, electronic mail, and information-bank access.

Right now, there's over 1100 MHz of amateur spectrum to work with, virtually unused (see Fig. 1). And that

1215*1300 MHz* 2300-2450 MHz 3300-3500 MHz* 5650-5925 MHz* 10-10.5 GHz* 24-24-25 GHz* 'Satellite operation permitted on part or at! of band.

73 Magazine publisher Wayne Creen W2NSD discusses the ham radio, satellite TV tie-in Ftg. 7. Practical microwave with Portus Barlow WA1DCP, president of Downlink: amateur bands.

doesn't include the 31 GHz allocated above 24 GHz, Best of all, there is great promise for low-cost equipment becoming available for the bands between 1 and 24 GHz.

What equipment, you ask? Well, consider the mountain ot gear available for 3.7-to4.2-GHz satellite TV reception Many hams have this equipment sitting in their backyards already, aimed at one of the eleven domestic {US and Canada) satellites. Hams already have played a key role in the TVRO technology that has exploded since Bob Cooper W5KHT "went public" in TV Guide. Here are some of the key developments:

• Bob Coleman K4AWB's plans for converting surplus microwave equipment.

• Oiiver Swan's revolutionary low-cost "window screen" spherical antenna, capable of capturing signals from several satellites,

• Taylor Howard WbHD's low-cost, do-it-yourself I VRO-receiver design.

• Bob Luly KAbKBU's 22-pound, 12-foot, portable umbrelia antenna,

• Steve Gibson's microcomputer-controlled antenna

• Clyde Washburn's 24-channel, tunable TVRO receiver.

The result of all this innovation: under-$4000, con-sumer-TVRO systems. For an idea of what the future might hold, see the box.

"The next logical step is to start working on low-cost uplinklng/' says Stanford University Professor Taylor

Howard. Let's take a look at how this might proceed. Right now, 1296 MHz seems to be the frontier with just a handful of pioneers using the band for EME (moonbounce). Steve Mieth W6YFK, for example, is achieving EME echo with an 18-foot TVRO-sty le parabolic antenna, 80 to 100 Watts into the feed, and a preamp with a 1-dB noise figure This sure beats those monster two-meter arrays and 1-kW rigs! Steve also has had some success on 2300 MHz with a similar setup, The 2300 band is interesting because of the dozens of companies manufacturing MDS receivers, as well as the surplus gear that is becoming available. Dxers with an eye on the 2400-MHz band may get a chance to try their hand at receiving signals from the

UoSAT satellite, scheduled for launch this fall.

Another interesting band is 3.4 to 3.5 GHz which falls right below the 3.7-to-4.2-TVRO band. We could easily adapt low-cost TVRO low-noise amplifiers and antennas for this band, to say nothing of all that surplus Ma Bell and military gear available. Combine those possibilities with the 5,65-to-5.925-GHz band, which falls just below the 6GHz uplink band. Power GaAs FETs and other transmitting devices are becoming avai [able, so we theoretically have the basis of a

What's Next?

Here's a sneak preview of what's coming in home satelflte TV. Watch for

• A $350 electronically-switched polarization device, eliminating need for mechanical rotation of the feed horn,

• An easy^to-build, complete TVRO pre-packaged kit for under $2,000.

• Microprocessor-controlled dish antennas and receivers for satellite selection and tracking and transponder scanning and selection, ail tied in with programmable VTRs full-blown amateur satellite communications system.

Consider this, again theoretically: Two Watts into the standard 12-foot-TVRO antenna is sufficient to communicate via a geostationary satellite with a 4-kHz-wide signal. For a full 36-MHz-wide video signal you'd need about five kilowatts.

That suggests some interesting possibilities. Why not lease a preemptable 4-kHz subcarrier on a commercial satellite? Think of it as a repeat er with very good range! Say, the entire US, Canada, and Mexico! To keep things under control, an encryption circuit could be built right into the transponder receiver. This would allow the common carrier {RCA, Western Union, etc) to shut out amateurs when the circuit was needed for another customer.

And what about the world of GHz and above? Hams are there experimenting, too, thanks to the commercial availability of Cunnptexers. The coming

Satellite TV net hams interested In satellite TV have been gathering on 20 meters, 14.310 MHz, starling at 1900 UTC on Sundays.

race for direct-broadcast satellite services wilf spin off some great equipment! Hams are already at 24 GHz during contests.

Taylor Howard W6HD offers some interesting thoughts about the specific developments that are in store for amateur radio He sees antenna feed design, lower cost detectors, and microwave-frequency filtering on PC boards as key areas. On the uplink side, W6HD believes we need to develop low-cost solidstate amplifiers, higrnstabil-ity multiplier chains, and inexpensive synthesisers. "The mystery is out of microwaves," Howard says, "and hams are the ones who will pioneer low-cost uplinking."B

References

Robert Cooper, "The Satellite TV Primer/' 73 Magaztne. November, 1979.

New Howard Manualt Coop's Operations Manual, Gibson Satellite Navigator; Washburn Receiver Manual, Nefson Antenna Manual, and Coop's Satellite Digest (monthly), all from STT, Box G, Arcadia OK 73007. The Home Satellite TV Bookt E, Terrence Easton, Playboy Press, February, 1982.

Satellite Channel Chart. Bimonthly guide to programming on all domestic satellites, including sports events. $15/year from WESTSAT Communications, Box 4341 Pleasanton CA 94566.

SATGuide. Monthly guide to SATCOM I programming. $36/ year from Commtek Publishing Co., Box 1700, Hailey ID 83333.

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