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Moonbounce from Arecibo Observatory
Last April hundreds of amateurs who had never had an opportunity to try operating Moonbounce finally got their chance.
Joe Taylor, K1JT, Angel Vazquez, WP3R, and Jim Breakall, WA3FET

F

or nearly half a century the world's largest and most sensitive radio telescope has been the 1000-foot reflector of the Arecibo Observatory, in Puerto Rico. O p e r a t e d b y C o r n e l l U n ive r s i t y u n d e r a cooperative agreement with the US National Science Foundation, the big dish is world famousforenablingpioneeringstudiesofthe Earth's atmosphere and ionosphere; of many objects in our solar system including planets, moons,asteroids,andcomets;andoferupting stars,cloudsofgas,pulsars,galaxiesandquasarsinmuchmoredistantpartsoftheuniverse. Hardly surprisingly, a number of permanent staff members and visiting scientific users of Arecibo are licensed radio amateurs. The three of us are among this fortunate group, each enjoying an association with the Observatory spanning more than 30 years. In 1972 Joe, K1JT, brought specialized equip-

menttoArecibothatenableddetectionofthe first known binary pulsar. He has continued to make frequent trips to Arecibo, usually accompanied by a small group of research students, throughout his professional career. Jim, WA3FET, first arrived as a summer student in 1974. He later conducted research for his PhD at Arecibo, providing new results on absolute calibration of the telescope and its high power radar transmitter, and finishing his doctorate in 1983. He has been involved since then with designing antennas for the Observatory.Angel,WP3R,joinedthetechnicalstaffasatelescopeoperatorin1977.Since then he has served as PC systems specialist and network administrator in the computer department, and most recently also as spectrum manager. Additional operators included our good friends Pedro, NP4A, and Angel, WP4G,whobroughtimportantoperatingand

technical skills and EME experience to the group,andvisitorPat,AA6EG,whorounded outtheteam. Needlesstosay,itwasgreatfunforusand other members of the Arecibo Observatory A m a t e u r R a d i o C l u b ( AOA R C ) t o p u t KP4AOontheairfor432MHzEME(EarthMoon-Earth, better known as moonbounce) over the long weekend April 16-18, 2010, using our all-time-favorite radio antenna. What a great QSO party it was! The telescope's huge forward gain, about 61 dBi at 432MHz,guaranteedthatevensmallstations could get into the game. Many hundreds of stations copied the KP4AO signal after its half-millionmileroundtriptotheMoonand back--someusingsmallhandheldYagisor evenadipole,andinatleastonecasearubber flexantenna.Thewallofstationsresponding to our CQs sounded like 20 meters during a

The 1000 foot antenna of the Arecibo Observatory.

Reprinted with permission © ARRL


The Arecibo feed-support system. The azimuth arm rotates about a central bearing; the "carriage house" (at right) and secondary reflector (inside radome, at left) move along the azimuth arm under computer control. In this way the telescope can be pointed to any direction within 20 degrees of the local zenith.

DXcontest!Evenwithskillful,well-behaved operators spread out over 15 kHz and more, wehadtoworkhardtopickcallsignsoutof the din. Wideband real-time recordings have enabledustocopyhundredsofadditionalcall signs,afterthefact.Atotalof242luckyones madeitintothelogwithcompletedtwo-way QSOs,inabout8hoursofactualoperation.

The Arecibo Antenna
Imagine a conducting sphere 1740 feet in diameter,restinginaholeinthegroundsome 157feetdeep.Cutthespherewithahorizontal plane at ground level, and remove the top portion.What'sleftisabowl-shapedreflector withtheoriginalradiusofcurvature,870feet, andadiameterof1000ft--justtheshapeand size of the Arecibo antenna. When constructionbeganin1962,mostofthenecessaryhole inthegroundwastherealready,thankstothe rugged "karst" geology of the region. The antenna's reflecting surface is made of some 39,000perforatedaluminumpanels,eachone individually adjustable, suspended from catenary cables and tied to concrete anchors in theground.Themeasuredsurfaceofthedish conformstothedesiredsphericalshapewitha root-mean-squareaccuracyof2.2mm. Unlike most other radio telescopes and large antennas built for space communica-

tion, the Arecibo reflector does not move. However,itsbeamcanbesteeredbymoving the feed antennas. The feed support system is comprised of a circular azimuth track and banana-shaped, 328 foot long azimuth arm, which rotates about a central pivot. Steering in zenith angle is accomplished by moving thefeedantennasalongatrackontheunderside of the azimuth arm. The large geodesic radome encloses secondary and tertiary reflectors and switchable feed horns to cover thefrequencyrange1-10GHz,plusanumber of lower frequencies ranging down to 327 MHz.Attheoppositeendoftheazimutharm there is a rectangular "carriage house" supporting the 96 foot line feed for 430 MHz. This feed is essentially a leaky waveguide; the rings are spaced so as to provide optimum illumination of the primary reflector. Other low-frequency feeds, for 47 MHz, for example,canalsobemountedonthecarriage house.Weusedthe430MHzlinefeedforour EMEsessions.

Equipment Setup for 432 MHz EME
Foroperatingconvenienceandtoprevent disruption to scientific programs scheduled in other parts of each day, we installed all amateur equipment at ground level, near the control room in the main electronics buildReprinted with permission © ARRL

The 430 MHz line feed.


a "CQ CQ from KP4AO, Arecibo Puerto Rico...,"andahugepile-uperupted.Fifteen SSB QSOs were made in the next few minutes; we then switched to CW and worked another74stationsbeforeourMoonwindow closed. It was disappointing not to have an amplifier ready for service on the first day, but for most of the calling stations it hardly mattered.Weweredelightedwiththetotalof 89QSOsmadewith35watts. A s s h ow n i n t h e f o l l ow i n g t a b l e , i n Saturday's Moon window we increased the QSO rate to about 40 per hour. Altogether our log shows 242 QSOs with stations in 36 DXCC entities. The accompanying waterfall image made from our recordings of our JT65B operation gives a good impression of thenumberofstationscalling.
A screen shot showing signals in a 4 kHz passband during JT65B operation. Many dozens of signals are present and easily copied.

ing. For the necessary feed line, some 1500 Semiconductor to the AOARC for scientific feet long, we used the permanently installed and educational purposes. As things worked WR2100 waveguide (0.04 dB loss per hun- out,wehadproblemswiththetubeamplifier dredfeet)normallyusedforthe2.5MW430 andwerenotreadywiththeSSPAonthefirst MHz radar transmitter. Amateurs who use day,sowerantheTS-2000barefootatabout waveguide for their microwave stations will 35 W. On April 17 we started with 350 W beamusedbythesheersizeofWR2100,with from the 3CX800 amplifier, but after an cross-sectiondimensions21в10.5inches. arc-overweswitchedtotheSSPAat500W. To obviate potential problems of mis- On the final day we used the 3CX800 again m a t c h e d l i n e a r p o l a r i z a t i o n a n g l e s , w e becauseaproblemhaddevelopedinthe50V elected to transmit and receive using right- powersupplyfortheSSPA.Murphytriedhis handcircularpolarization.Asignal'ssenseof best, but we were well supplied with spares circularityisreverseduponreflection,sothe andservicingskills. most efficient reception would use left-hand circularpolarization.However,the3dBloss On the Air! for stations using linear polarization would Notice of our scheduled operation had be of minor importance, and there would be beenpublicizedforonlyafewweeks,butthe no problems with mismatched angles. Since grapevine was so efficient that hundreds of wereceivedonlythecross-polarizedsignalin stationswerelisteningforuson432.045MHz ourownself-echoes,theywereattenuatedby atthetimeofourfirstMoonacquisition,1645 some15­20dB;however,theywerestillS9+ UTConFriday.Abrief"Hellooo...Moon!" inourreceiver. on SSB to check our echo was followed by For extra flexibility we used two Kenwood TS-2000 transceivers -- one for transmitting and one for receiving. The receive side included a GaAsFET preamplifier with noise figure 0.5 dB and equivalent noise temperature 35 K. The telescope beamwidth is only 0.15° at this frequency, less than1/3thesizeoftheMoon'sdisk. Consequently, our system noise temperature was dominated by the Moon'ssurfacetemperature,about 210K.Totalsystemnoisetemperature including receiver noise, feed line, waveguide and rotary-joint losses,andantenna"spillover"was around350K. We had two power amplifiers available -- one using a 3CX800, andtheotherasolid-stateunitbuilt Angel, WP3R, connects LMR-900 feed line to a waveguidebyF1JRDanddonatedbyFreescale to-coax transition, just outside the transmitter room.
Reprinted with permission © ARRL

SSB CW JT65 Total Friday 15 74 0 89 Saturday 75 31 0 106 Sunday 16 17 14 47 Totals 106 122 14 242 As had been planned and announced in advance, an hour of Sunday's window was allocated to the slower but extremely sensitive digital mode, JT65B. It was impossible to work more than a tiny fraction of the stations that were calling. We tried to pick out someoftheweakerdecodablesignals,making a total of 14 QSOs in our final hour of Moontime. Even with reasonably good signals in both directions, it is not possible in any modetorunanEMEpileupattheQSOrates sometimes achieved by top contesters or DXpeditioners.Aninevitable5seconddelay (twicetheround-triptraveltimetotheMoon, at the speed of light) occurs between each station's standby and the first echoes heard from a QSO partner. Moreover, we wanted torespecttheminimal-QSOstandardsgenerallyusedintheEMEworld,which include full exchange of both call signs,asignalreport,andacknowledgments. We provided live video and audio streaming of the whole operation, and many viewers were a m u s e d b y t h e s c r e e c h e s f r o m tropical birds inadvertently sharing our transmitter room, as well as plenty of human noises from lookers-on.Wehopethesedistractions have not caused a significant numberoferrorsinloggingthestationsworked.

Soapbox Comments
Wecouldtellmanymorestories aboutthegoings-onatArecibo,but in many ways the most interesting ones will be told by operators at the other ends of our EME paths. Herearesomeselected(andlightly


JoeTaylorisanARRLmemberfirstlicensedasKN2ITPin 1954,andhassinceheldcall signsK2ITP,WA1LXQ, Persistence paid off...25 W1HFV,VK2BJXandK1JT. elements and a 100 W brick HewasProfessorofAstronomy amplifier was enough for a attheUniversityof QSO. -- WB2SIH. Nice to Massachusettsfrom1969to listentotheKP4AOSSBsig1981andsincethenProfessor n a l w i t h a s i m p l e s t a t i o n : ofPhysicsatPrinceton University.Hewasawardedthe 1 2 - e l e m e n t Ya g i , 0 . 5 d B NobelPrizeinPhysicsin1993 LNA, homebrew converter fordiscoveryofthefirstorbitandSDRreceiver.Honest55 ingpulsar.HechasesDXfrom to 57 signals. An awesome 160metersthroughthemicroexperience!--PY3FF.Very wavebands.Joecanbe impressive on JT65B! Was reachedat272HartleyAve, sendingeveryperiod,butmy Princeton,NJ08540,or flea power of 50 W and a k1jt@arrl.net. AngelM.Vazquez,WP3R,is 16-elementYagididn'tcutit. anARRLmemberwhowas -- E51WL. Tried for hours borninArecibo,PR,butraised onSSBandCWwithoutsucinBrooklyn,NYfromtheageof cess; was very surprised to The tired but happy operators are (left to right) WA3FET, K1JT, WP4G in 2untilhegraduatedfrom make it with the tremendous front of WP3R, and NP4A. AA6EG was behind the camera. CUNYwithanAssociate pile up when you went to degreeinElectrical JT65! Huge signals here on Engineering.Heachieveda mysingle28-elementYagi.I FirstClassRadiotelephone suspect after this weekend more stations Cushcraft719Bona6footstepladder,50feet FCClicenseandworkedoneyearforWNYC will be encouraged to have a go at 70 cm o f L M R 4 0 0 . C o p i e d o n S S B , C W, a n d asaRadioEngineer;in1977hemovedto EME.--G4ZFJ.Icalledforafewminutes JT65B. -- NJьU. Thanks for my first EME PuertoRicoandtookapositionattheArecibo soon after your Moonrise, not really expect- QSO in over 30 years! -- KьTV. Feeling Observatory.Positionstherehaveincluded TelescopeOperator,SeniorTelescopeOperator, ingto beheardthrough thepile.Afterabout proud of being a ham! Using a 10-element SpectrumManager,PCSystemsAdmin,RFI tenminutes--loandbehold!--theoperator Yagi and an FT-817, I desperately tried to ManagerandHeadofOperations.Youcan came back with "W4RBO 59." I almost fell contactKP4AOinJT65B,butdidn'tsucceed. reachAngelatHC3Box53995,Arecibo,PR out of my chair. -- W4RBO. A 21-element Nevertheless I felt like Jodie Foster in the 00612,orangel@naic.edu. ARRLmemberJimBreakall,WA3FET,was Tonna with az/el pointed manually, SWR movieContact!--LY2SS.Useda3-element 2.5:1,20metersofcoax,FT-817,nopreamp. Yagionwoodenpicnicbenchinbackgarden, firstlicensedasWN3FETin1965.Hereceived S i g n a l wa s fa n t a s t i c , p e a k i n g u p t o S 3 . pointedroughlytowardstheMoon,withpre- BSandMSdegreesfromPennStateUniversity --HB9DRI.SetupontheNewJerseyshore amp and about 20 meters of good quality andaPhDinElectricalEngineeringand AppliedPhysicsfromCaseWesternReserve. withasingle12elementYagionaphototri- coax to an ICOM R9000. Good copy in HeworkedattheLawrenceLivermoreNational pod, 15 feet of RG-8 into an FT-847. You JT65B mode on Sunday! -- Chris (SWL Laboratory,mainlyondevelopmentofthe were Q5 throughout on CW. -- W2KV. in UK). Great fun listening to the fantastic NumericalElectromagneticsCode(NEC)used F i f t e e n s t u d e n t s bu i l t 4 - a n d 8 - e l e m e n t signal and the pileup of stations calling. tothisdayforantennamodeling,andtaughtat Yagis, all 1 meter or less in length. With the -- SM2CEW. KP4AO peaked 57 on side- theNavalPostgraduateSchoolinMonterey, help of an 18 K preamp, copied your 35 W band; perfect copy, hardly a word missed. CA.PresentlyheisProfessorofElectrical CW signal on every one! Then worked you U s e d a n 8 - e l e m e n t Ya g i , b o o m l e n g t h EngineeringatPennStateandworksmainlyon e a s i l y u s i n g o u r 1 6 в 1 0 - e l e m e n t a r r a y. 0.8 meters, with one of my own LNAs, antennas,notablyfeeddesignsforthe1000foot Arecibodish.Heisafrequentspeakeratthe -- WD5AGO. Very strong signals! Made 0.3 dB NF and 27 dB gain -- G4DDK. AntennaForumattheDaytonHamvention,and c o n t a c t i n S S B a n d a l s o m y d a u g h t e r, O S C A R 1 0 - c l a s s s t a t i o n w i t h 4 3 6 C P 3 0 hasbuilttwomajorcontestsuperstations, S W 8 NAC ( 1 2 y e a r s o l d ) m a d e a n S S B antenna, 150 W through 110 feet of Andrew K3CRandKC3R,nearPennState,andWP3R, QSO.--SV8CS.FT736RandMirage100W FSJ4-50B.SolidcopyonCWandJT65B.My onhisfarminPuertoRiconearthebigdish. brick,KLM432C18circularlypolarizedsat- first EME QSO on 70 cm, and hopefully not HissonisJimmyBreakall,W3FET,whogothis elliteantenna.Allmodescopiedhere,butwe thelast.--W1ICW.Nicetostillfindathrill licenseattheageof9.Youcanreachhimat 225ElectricalEngineeringEast,PennState couldn'tbustthepileups.--K7IP.OSCAR after30yearsofhamradio!--9H1GB. University,UniversityPark,PA16802orat 13 station, IC-7000, and home-design cross jimb@psu.edu. Acknowledgments Yagiwith13+13elements,15metersof9913 PhotosoftheAreciboantennaand Many people at the Arecibo Observatory coax. RST 419 in CW mode, JT65B tones thefeed-supportsystemarecourtesyofthe clearly audible in speaker. -- LU8YD. Too worked hard to make this event successful. NAIC--AreciboObservatory,afacility badyoudidn'thaveamonthofMoontimeto We especially wish to thank Israel Cabrera, oftheNationalScienceFoundation. work all the stations calling! -- NY2NY. KP4LCL, who loaned his TS-2000; Alfredo RemainingphotosarebyWP3R,K8YUM FT-857 and 100 W brick, single 11-element Santoni,whogavegenerouslyofhistimeand andWP4G. WA5VJB cheap Yagi on tripod, no preamp. engineering skills; Dana Whitlow, K8YUM, Solid copy all day on Sunday at ­11db on who made the wideband recordings; Mike JT65B.--W6OUU.I'msurethatthanksto N o l a n , O b s e r va t o r y S i t e D i r e c t o r, w h o this event EME will see a big increase of granted us the necessary telescope time, and a c t iv i t y in th e fu tu re on CW an d JT 65. Pat Barthelow, AA6EG, who made the iniM a n y n ew s t a t i o n s h av e t a s t e d b l o o d ! tial inquiry and suggested possible dates of --CT1HZE.FT736Rbarefoot,nopreamp, operation.

edited) comments that we receivedaftertheevent...

Reprinted with permission © ARRL