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Wayne Green II WGE Center Peterborough NH 03458

Born: 1922 Class: Advanced

Hamsats_

Amateur Radio Via Satellite

Andy MacAMster WA5ZIB 14714 Knight sway Drive Houston TX 77033

Satellite Operation Today

A decade ago. few would have relieved the day would comc when there would be so many operational amateur radio satellites that one could be above a station's horizon almost continuously Today we have 13. It you count the Russian space station Mlr> with its 145,55 MHz packet BBS. we have 14 With multiple transponders on most of the spacecraft satellite chasers have many options ranging from HF to microwave activity

Although some might consider the HF transponders on RS-12 and RS-13 for relatively short-range con I acts, others have round them to be a medium for worldwide communication. Using Ihe Mode K transponder on RS-12 {uplink 21 210-21 250 MHz. downlink 29.410-29 4SO MHz), overlhe-honzon DX is possible when skip condrtron^ permit it A complete frequency chart tor RS-12/13 is m the May 1991 'Ham-sats,*H

For the UHF and microwave enthusiast, the Mode S transponder on AMSAT-OSCAR-13 (uplink 435,603435.639 MHz downlink 2400 7112400.664 MHz) has provided many opportunities io work with 2 a GHz equipment and make worldwide contacts via, satellite.

Mosi satellite chasers preler Mode A {2 meters up and 10 meters down) via RS-10/11 or Mode B (70cm up and 2 meters down) via A-O-13 Or A-O-IO. While RS-10/11 is in a low-earth orbit (several hundred miles high}. A-O-13 and A-CmD are in highly eilrpticaJ orbits, traveling oui past 20,000 miles at apogee, the orbit's fanhest point from the earth Even though the elliptical orbit satellites have gain antennas and high power transponders, ground stations will need quality aniennas and expensive equipment for easy contacts The RS-iO/11 station is usually less complex but the satellite's coverage is also less, due to ihe lower orbit.

Since the launch earlier (his year of RS-14, also known as RADIO-M1, RUDAK-2 or AMSAT-OSCAR-21, hams have had a Mode B Iransponder in low-earth orbil requiring only omni antennas like ground planes for consistent contacts via satelliie The May 1991 "Hamsats" also had a frequency chart for this hamsat.

Simple Earth Stations

Getting active via satellite can be easy. To wor+t RS10 Mode A. all that is required is a good 10 meter receiver with a dipofe and a 2 meter Transmitter capable of CW or SSB with an omnidirectional antenna

Some FM ngs are capable of CW

uplink by keying the microphone push-to-talk switch but many will exhibit excessive chirp with this method, tt's worth a try An alternative is a used, multirrKXie 2 meier rig. One can usually be found for a few hundred dollars at a swapfesi Inexpensive older rigs to look for include the Kenwood TS-700A. Ihe Yaesu FT-480R and the ICOM IC-251. A simple quarter-wave ground plane antenna for 2 meters can be purchased or made from coat hangers and a SO-239 connector The L akeview Co model GP-10-2 by WD4BUM is a very nice ground ptane thai can ne quickly assembled ior easy portable operation Another good choice would be the MAX System ground plane antenna from Cellular Security Group.

On a recent tnp out west 1 used a Lake view antenna for many successful contacts via RS-10 My uplink power was about 10 watts through 20 feet of RG-8 coax, For the downlink, I stretched a dipole made from hook-up wire between two trees. The feedline was a short run of RG-58 to a Uniden HR-251G. Although a sm.ill MOSFET preamplifier was available, it was not necessary for most contacts A 12 volt power supply powereo the radios, but a battery would have done the job as welt.

Operation via ihe Mode B linear transponder on A-O-21 proved to be just as easy as A on RS-10. Ten watts to the 440 MHz version of the Lakeview ground plane proved sufficient for quality contacts whenever the satellite was above the horizon. A GaAsFET preampJilier was employed for the 2 meter downlink It wasn't necessary, but it helped during times when the satellite was low in ihe sky

Although I didn't try ii during the western trip, mobile operation should do very well on A-O-21 A smgle quarter-wave whip ior 2 meters could be used for both 70cm uplink and 2 meter downlink. A dipiexer would be needed, but they have become very common in recent years due to the popularity of dual-band mobile operation through FM repeaters. For those interested in building their own, the September 1969 issue of Nam Radio presented a very simple, easy-to-build diplaxer in the Ham Notebook" column

The success of A-O-21 activity with nothing more than ground plane antennas was inspiring. AMSAT-OSCAR-13 was oriented to provide excellent signals after apogee (when the satellite is closer) rather than during 1 had been able to hear conversations in ihe passband with the ground plane and preampr so i tned the 70cmuplink. Signals were so weak 1 could barely hear my own CW, but ¡1 was there Afler several attempts at contacts, a very patienl W06EPV came back with an answer to my call. Ten watts to a ground plane is not much for contact via a satellite 15,000 miles away, but ii will work under optimum condi-lions, and if the operator on the olher end has a good system and an excellent ear.

Other Simple Systems

It's not necessary to see how small an antenna system can be and stiN work for satellite activity. A lew hams have put their stations n backpacks and used shoulder-mounted beams to make contacts via the high-orbit ham-sat s Others have had simple, yet effective. stations an boats, and several have tried mobile satellite work. Field Day is another opportunity for innovative installations.

The idea is to use available equipment to make contacts via satellite, and add system improvements for more serious efforts as time and money allow. An omnidirectional antenna on 2 meters can be the beginning of a home satellite system with the inclusion ol atmosl any 10 meter rig and antenna, For that matter, the simple 2 meter home antenna could be immediately put to good use making contacts with U5MIR-1, the packet BBS on Mir (145.55 MHz FM simplex) Similarly, sfgnals from DOVE-OSCAR-17 and UoSAT-OSCAR-11 can be monitored wilh simple systems tuned to 145-825 MHz FM.

The addition of at least one beam antenna with azimuth and elevalion control marks the beginning of serious satellite activity Expensive computer-con ti oiled rotators are not necessary. Jack KA5DNP. author of "The Field Day Special—ihe Ray Gun' " in the June !990 issue of 73. doesn't use rotators at all, and has DXCC via satellite. Older TV rotators provides excellent service if you need remote control or who wish to pursue fast-moving, low-orbit birds. HI

Pftofo 8 Typical Field Day satellite antenna system for 2m and 70cm
Photc A. WA5ZIB and WA5WOD wtth portable station in central Texas

THE ANTENNA EXPERIMENTER'S GUIDE

200 pages 120 .. MraUExr^ includes matana; not pf >»viausly pubEisfied. Budding RF tea equipment. antennae and AlUma QpfirnizFig ana modoSng. Computar measurementr & modeling i

Price $15, P A I* $2 mirfict mall, U dr mill. Cash or VJsj 37 The Rldlfiga, E iid Pre^on, Wust Su*MX BM16 2TW, U K Tal 011 7V&BCM

circle 92 on reaper service card

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