Radio Technique

George M Mye 7Radomchnque ABSTRACT How use formation ob tained scanner PREFACE In AMA position frequency co ordinator District II receive requests loan scanner AMA has assigned district usually interrogate requester find out what kind troubles being investi gated usually turns out can solved mathematically rest usually think futile monitoring effort will be cause person will monitoring doesnt know what look foror iden tify usually think futile moni toring effort will because per son will monitoring doesnt know what look foror identify flurry inspiration morning put together passed around lot peo ple comments make complete ac curate possible within scope simple handbook wanted hope will find helpful What scanner can youan overview scanner radio receiver automatically sequentially tunes list preset frequencies lets listen radio transmissions dont understand significance what hear dont learn anything get scanner district frequency coordinator tendency turn go looking voice transmissions cause can understand can find voices some frequencies shouldnt find voices 72 MHz RC channels because have channels exclusively Does mean free interference really key finding interference knowing what look look kinds radio transmissions familiar sound 55-16 MHz AM 88-108 MHz FM broadcast radio because have automobile key finding interference knowing what look forand look know about 26995-27255 MHz Citi zens Band RC channels supposed free voice interference monitor 50-54 MHz Amateur fre quencies others possible hear voice Morse code slow-scan TV packet radio bursts digital data teletype and/or digital bit-streams may AM FM PM [phase-modulatedi systems single-sideband transmttters etc think familiar sound 54890 MHz TV because have set liv ing room sound TV just soundtrack movie FM sound way vertical oscillator sput ters 60 Hz horizontal oscillator squeals 1575 kHz picture signals supersonic things 72-73 MHz MRS/PRS/ RC band carry voices such mobile tele phones also pocket pagers sometimes sound like fast telephone push-button tones sometimes sound like sleigh bells even-frequency chan nels between 10 kHz away RC channels Depending scanner designed may hear some things 108-135 MHz aircraft radio band such VOR air plane radio navigation aid low BRRRBRRRBRRR accompanied Morse code incidental transmitters com puters welding machines lightning strikes highvoltage transmission lines sometimes coro na on strongly recommend use tape recorder tool ke notebook Record sounds scanner talk recorder setting up tests ad justing scanners controls point Im making lot hear Identification interpretation what hear important hearing article will help teach yourself interpret some what hear Since aural experience strongly rec ommend use tape recorder tool learn ing Use like notebook Record sounds scanner talk recorder setting up tests adjusting scanners controls could make such tape work wont thinking wont learn anything Lesson #1 sounds RC systems else failsREAD THE BOOK will tell turn scanner make its tricks Bill Hershberger has written manual interprets Japanese techno-speak sim ple English sketches control locations added manual should available AMAs scanners time published Recess read Bills manual Welcome back Now lets discover differ ence between sound AM FM FM/ PCM turning various RC sets listen ing scanner will quickly learn tell difference between simple twoor three-channel AM set complex multichannel FM/PCM RC system just listening Lesson #2 Signal strengths squelch controls have go outdoors lesson good procedure have someone walk down road operating RC transmitter listen scanner work scanners controls get best results will learn lot about squelch control af fects what hear will also learn about dropouts transmitter scanner whip antennas held vertically 13 ft transmitter moves away scanner signal will drop minimum' best once road doesnt have electric wires poles alongside sec ond time road does makes differ ence ground suspended electric wires overhead continuous metal fence nearby buried wires pipes below join sig nal transmitter scanners tenna probably wont hear anything after transmitter one-half mile away scanner Keep track signal strength S meter reading function distance transmitter Plot signal strength versus distance will also learn about dropouts transmitter scanner whip antennas held vertically will observe 13 ft transmitter moves away scanner signal will drop minimum Dropouts close transmitter noticeable between dropouts signal will peak maximum Observe variations S meter Put scanner antenna horizontal point operating RC transmitter itend onfrom about 150 ft away Note signal strength 5 meter Have person holding trans mitter slowly rotate tip-on-the-ground position vertical position watch S meter signal should rise maxi mum transmitter antenna inclined about 45 0 fall new minimum 900 vertical Have person transmitter hold ver tical high over head possible Ob serve effects S~ meter Write down S meter indications versus antenna angle few data points plot yourself curve 38 Model Aviation 70 Froehlkh Farm Rd Hkksville NY 11901 What can learn scanner Pre tend months column book Table Contents Preface What scanner can youan over view Lesson #1 sounds RC systems Lesson #2 Signal strengths squelch controls Lesson #3 sounds adjacent channels Lesson #4 Third-order intermodulation Lesson #5 Other sounds intermodulation a First orderdirect interference b 21MThe 23-channel problem c ImageThe 455-channel problem Lesson #6 much stuff really interference Commencement address .. dont understand sig nificance what hear wont learn anything have learned something about effects tenna orientations height Overall will develop some understanding dynamic range signals could fly over about 20 ft would hear dropouts caused phase cancellation relates fact radio signals travel faster air ground exact speed difference affected moisture soil phase cancellation effects cause var iable Ordinarily will show up changes ground range test distances difference tween ground range measured over freshly watered golf course compared over dry sand can significant Sensitive airplanes may glitch ie lose con trol momentarily result dropouts causes airplanes usually fly through dropouts quickly go unno ticed Helicopters other hand might unlucky try hover dropout region should tell something about hovering along altitude some distance transmit ter PCM helps overcome dropouts .. pair transmitters 23 channels apart might affect wideband SC455 air regard what RC channels on #3 sounds adjacent channels Set scanner 72680 MHz set up transmit ter RC44 shouldnt hear anything unless RC transmitter too close Move RC transmitter slowly 3 ft away 100 ft away Note signal changes scan ner has wideband/narrow-band switch once switch position note results What hearing similar what receiver hears adjacent MRS/PRS channelwhich transmitters located between 10 kHz away RC channels Note 5 meter reacts Scan 7200 through 7300 MHz may observe strong signal can heard three channels sequence eg PR5375 72540 MHz RC38 72550 MHz PR5385 72560 MHz wideband transmitter leaking onto adjacent channels 10 kHz awayadjacent channel interference defi nition Lesson #4 Third-order intermodulation easy since 31M signals generated RC transmitters always exactly centered RC channels can always heard scanner Put scanner 72590 MHz RC4O leave Set up operating RC44 transmit ter 100 ft away scanner Have another club member stand about 3 ft RC44 transmitter turn RC42 transmitter should hearing 31M RC4O Scan slowly 7200 7300 MHz looking other signals should find 31M 72650 727 10 MHz Note loud record signal strength 5 units Stop scanner see 31M sound goes away transmitters turned off have transmitter available chan nel 31M put transmitter op eration see far away can taken before 31M can heard learning about relative signal strengths Turn several transmittersthree four five six moreat same time sequence Space 30 ft apart line per pendicular line scanner Scan World S t best sellfl9 Spark lgfltt0O Systemi V Oiasen Byron 0riuhds TEtG Mfg uid kM Aircraft Sqiply tar its outstuuhlg ralility Complete single cylinder system including throttlecoupled spark advance kit spark spark plug lead25 plug battery pack charger 900 sh elded Much huger onpue lie Easy huid stals-no kickback 1-12D90 RPM rabble hUe 0% nore power tear strokers om histabtion avielile Slielded spat pleg lead mel 9W ph cover Lower waded FummyenpiesUitmp2&4stroke siqeaidtwhicyhders zolpouhictsavddale Smut cob gawk phiw dieldal pha lead B Ihckw kits avale B&P Associates Gives Total Flight Line FREEDOM battery needs call write B&P Associates PO Box 22054 Waco TX 76702-2054 817662-5587 new electric starter battery pack cuts cord has always tied starter power panel Discover freedom being able start plane wherever added safety less wire get caught prop charge hefty 4 Amp/hour pack will take through weekend flying power enough spare dont stop have Ni-Cads virtually size imaginable cut experimenter free design whatever takes make yours best setup field August 1989 39 72 73 MHz smallest available steps squelch control turned way down CCW helps AM transmitters FM transmitters PCM trans mitters mix sounds differ ent doesnt now should able tell what transmitter types making up intermodulation package just listening get ting education Now turn off transmitters except two Put butt-to-butt Scan 7200 7300 MHz Notice anything familiar Two transmit ters butt-to-butt sound like bunch transmit ters physically separated dont Thats call arrangement Flight Line Simulation test setup rule 31M Any two transmitters will generate 31M frequency midway between operating frequencies far above below frequencies separated frequency Somebody has access spectrum ana lyzer will tell 31M signals about 30 dB below transmitter signalwhich true Other people familiar properties RC receivers will tell interference oc curs spurious signal received 15 22 dB below received control transmitter signal Note means weak signal interferes control strong signal difference signal strengths 8 15 dB margin safety 3lM interferenceall things being equal studies signal strengths dropouts will have convinced things never equal Signal strength drops rapidly distance control transmitter increases drop Outs lower transmitters usual signal 15 dB easily demonstrated changes relative antenna positionsas have seen yourself should able have opinion about what people tell some 31M examples 1 RC30 RC4O will generate 31M RC2O RC35 RC5O 2 TV4 sound carrier 7175 MHz RCl3 can produce 31M RC28 other TV4 combinations like RCl8 RC38 RC23 RC48 RC28 dumps 31M both RCl3 RC58 strength TV4 signal determines whether resulting 31M will bother anybody have access Kraft synthesizer transmitter can easily check situation Out Remem ber write down signal strength 5 un its will use information Lesson #6 suspect channels RCl3 18 20 21 23 28 38 48 58 presence strong S 4 signal measured flight line Note RCl3 RC2l will new considerations 1991 dont have strong TV4 signal area may have something else like TV5 microwave beams Microwave beams very narrow likely affect plane particular spots sky may able hear scanner tow ers easy spot tiny dishes pointing parallel ground can take list frequencies work out combinations own based what find have evaluate whether 31M signals strong enough con sidered interference Lesson #6 somewhat limited assessment fact scanner ground doesnt hear much does airplane receiver air Lesson #5 Other sounds intermodulation First easy Turn two RC4O trans mitters same channel same time Set scanner channel listen first transmitter both should hear super heterodyne whistle among other things come second transmitter Thats First Order Intermodulation Pretty loud isnt can hear scanner happens b Now difficult problem interferences generated inside receivers cant hear because scanner receiver differ ent RC receiver have find some thing apply some reasoning some math ematics earn pay DFC lesson must have pencil paper page 10 Membership Manual ad dition scanner tape recorder 21M 23rd-channel problem rule 21M Take operating fre quency transmitter add subtract TRAINERFOAMAIREMONARCH SPAN 10$IA 095 SPAN 74SPAN 10 WEIGHT 2 lbs WEIGHT 65-75 lbs $O95 WEIGHT 2 lbs $164 POWER 0 00$IAgs POWER 0POWER 0 cc 3 4 CHANNEL4CHu1-IFOUR CHANNELFOUR CHANNEL CALL OR WRITE FOR FREE INFOART 1 NEODESHA KS 66757 ON SAC KITS AND QUADRA PRICES,./-Ij316 325-2821 FREE SHIPPING ON KIT ORDERVISA / MASTERCARD ACCEPTED 40 Model Aviation OPSorYS parts close 1-800-535-2568 Dealer Inquiries Invited SThe Part Cm*ea~% 9miai4 9#ce BIRCH PLY WOOD 1/64o12o12/7s1/40601274 1/640120243501/4012012146 1/640120497001/4012024293 1/64 0 46 0 4626001/4 0 12046565 BALSA WOOD STICKS 1/16-INCH3646 1116 111606 1/1603/3207 1/1601/60811 1/16o3/160913 1/160 1/41015 1/1603181217 1/160 1/21620 1/1603/42126 3/32-INCH3646 3/3203/320611 3/32 0 1/60913 3/32 03/161015 3/320 1/41316 3/32s3/81419 3/320 1/21621 3/32 0 3/42431 Double Balsa Wood Prices Spruce Basswood Sticks 1/6-INCH3646 3/8-INCH3646 2737 1/80 1/60811 1/Bo3/161119 1/60 1/41317 1/6 3/61621 1/60 1/21724 1/603/42523 3/I 6-INCH3646 3/1603/161317 3/16 1/41419 3/16s3/61621 3/160 1/21625 3/16 3/42636 1/4-INCH3646 1/4 1/41621 1/403/61625 1/40 1/22129 1/4 0 3/43142 5/16-INCH3646 5/16 9/162027 5/16 0 3/82230 9/160 1/22736 9/16 0 3/43952 3/6 0 3/6 3/60 1/23041 3/6 0 3/44460 1/2-INCH3646 1/2 0 1/23749 1/203/45270 TRIANGULAR CUT BALSA 1/401/403624 3/903/603629 1/201/203637 3/4o3/4o3647 10103661 BALSA PLANKS 3/403036176 102036164 1o3o36230 104036303 202036230 203036329 204036464 303036490 304036690 BALSA SHEETS I-INCH3646 1/160 I2736 3/32 0 13040 1/8013344 3/16 0 13749 1/4 0 14157 3/6 0 I6372 1/2 0 16999 2-INCH3646 1/32023040 1/16023646 3/32 0 24154 1/6024660 3/16025472 1/4026364 3/60277103 1/202113150 3-INCH3646 1/32034053 1/16034356 3/32 0 36270 1/6036090 3/16 037290 1/40364112 5/1603103134 3/603120160 1/203160200 4-INCH3646 1/32046597 1/160473101 3/320462109 1/60495126 3/1604114151 1/404131193 3/604162271 1/204219325 1/320601252 1/320120 12105 1/32 012o 24210 1/32012048420 1/15o6o1252 1/ISo12012105 1/15012024210 1/16012046420 3/320501261 3/32o12012163 3/32 0/2o24326 3/32 012046652 1/6o6o1299 1/90120 12179 1/So12024356 1/6 o12 0 40712 3/160601274 3/16012012146 3/15012024253 3/16012046565 Superior Aircraft Materials 3/80120 12160 3/6 o12 0 24360 3/6 o12 046720 1/20 120 12202 1/2 0 12o 24405 1/2o12o49606 LITE PLYWOOD 1/6o12o1256 1/9 0 12o24112 1/6012049224 TAPERED TRAILING EDGE3646 1/60 1/22230 3/16 0 3/42940 1/40 14255 5/16014461 3/60 15272 12020-G Centralia iian Gardens California 90716 865-3220 Handling Charge-$500 $300 COD mum Order $2000 FOB Factory accept Personal checka COD fornia Residents add 6% Sales Tax receivers intermediate frequency find po tential interferer common intermediate frequency 455 kHz 455 MHz Narrow-band SC455s less likely af fected 21M wideband SC4SSs SC le-conversion Thats because possible 21M interferers S kHz away RC channel narrow-band receiver can ig nore Narrow-band SC4SSs becoming available Lets say find something 72500 MHz Add 455 get 72955 MHz closest RC channel RC58 72950 MHz 5 kHz away might produce interference RCS8 receiver signal 72500 has strength S C455 receiver wideband Something worse pair transmitters pair 23 channels apart might affect wideband 5C455 air regard what RC channels Its matter relative signal strengths general wary signal over -5 dBM easiest way evaluate test field airplane Let airplane ground tell disturbed doing ground range test noticing whether distance shorter usual arent finished yet Now look oppo site direction 72500 72045 closest RC channel 72050 MHz Again might suffer interference RC58 didnt best test field test Heres 21M example find FM sound TV4 71750 MHz has signal strength -4 dBm 2 Looking upscale 71750 72205 MHz between RC2O RC2I closer RC2I Because FM sound fre quency wobbles bit isnt exactly 7175 MHz times So might get hit either chan nel course manufacturers know expect will put local oscillator channels above transmitter because way local oscillators defined para graph 410 AMA Radio Control Utiliza tion Plan page 11 column 1988 Mem bership Manual have avoid simultaneous flying RC43 RC44 high-band channels will have check out TVS paragraph 410 AMA Radio Control Utilization Plan page II 1988 Member ship Manual changed put local oscillators outside 72 MHz band thereby minimizing 21M between modelers intermodulations TV4 TVS can problem best lution might stay off RC2O RC2 1 alto gether insist flying 5C455 re ceiver presence strong S 4 signal However 21M isnt confined SC455s Any receiver can affected 21M case dual-conversion receivers first conversion usually has local oscillator 1155 MHz away control transmitter much off set front end usually can attenuate potential 21M signal insignificance So doubt owners dual-conversion RC receivers have reason worry about 21M Yes 21M between modelers wont become problem until 199 Iand 50 chan nels sanctioned planned oddnumbered RC channels create problem cause pair transmitters 23 channels apart can cause difficulty Using even-number ed channelsas doing right nowthere no problem already have MRS/PRS transmitters separated RC channels amount can expressed 22 RC channels plus 10 kHz example would relative RCI6 16 lus 10 kHz RC36 plus 10 kHz just likely generate 21M existing 5C455 Rx RC channels 23 numbers away complaints received various locations around country LA Denver Atlantic City seems doing depends sig nal strength flying field So have find MRS/PRS transmitters consider what capable doing c image frequency Any receiver sub ject image interference practical stand point SC455sonRCll 12 13 14 57 58 59 60 have anything worry about Continued page 131 August 1989 41 TAIBI PRESENTI FLINGER THE ULTIMATE SMALL SAILPLANE HANDLAUNCH HI-STARTorSLOPE WINGSPAN 57 WEIGHT l2oz MACHINE CUT PARTS DEALERS&DIST INOUIRIES INVITEDFLINGER LJMP 110 $2995 ELECTRA L ITE-ICARUS-PANTERA- METEOR-ELECTR ICUS-WHISTLER PRELUDE-COMET LARRY JOLLY MODEL PRODUCTS 5501 W COMO SANTA ANA CALIFORNIA 92703 714 826 6861 Letters Editor Continued page 11 Ni-Cds dont seem affected cold anything like alkaline cells Once problem corrected lit tle Nickle flew flawlessly greatest small three-channel airplanes have ever flown James Harris Marion OH Safety/Preston Continued page 22 fit inside muffler between bolt holes will stop two halves warping have done three G-38s havent problems mufflers coming loose Now respect firewall fire picture column builders Giant aircraft would use engine mounts made engines flat plates come would have air gap behind muffler cool ing gasoline engines run hot dont think put hand hot muffler like did five years ago Thanks have taken time write describe mishaps Without letters would no Safety column wish another safe month Sweepee/DhaII Continued page 37 wont take off until its ready airplanes slow speed flying characteristics indicated also peculiar com ing out near hover increase throttle gradually ease off elevator stick using little down control get some extra speed Try maneuvers safe al titudes beginning youre getting used airplanes foibles might also find need get acquainted its strange appearance air before attempt ing anything too fancy color scheme clearly distinguishes front plane back should come handy low throttle condition flight charac teristics model similar sport airplane until force high angle attack slow speeds gradually increas ing up control seems have little effect airplanes attitudebut does bring model virtual halt point sink rate will high probably will have keep rudder control active keep course However plane shows relatively little tendency stall out condition Im still exploring full range SAFE FLYING IS NO ACCIDENT airplanes flight characteristics Join search Discover Sweepee yourselfand happy backward flying Radio Technique/Myers Continued page 41 must wary transmitters 910 MHz 455 channels away Such transmitters MRS/PRS transmitters find strong signals S SlO5 115 125 135 145 565 575 585 595 605 have consider potential interferences xx5 shorthand code PRS channel 10 kHz above RC channel number given Channel 105 0 MHz Image example strong signal S und 72040 PRS 125 may interfere 5C455 receiver channel 125 RC58 summary find something scan ner note its frequency some mathemat ics see what found might problem Lesson #6 much stuff really inter ference looking signal 72xxx MHz has strength 55 nd can expect signal adjacent channel problem wideband receivers air Expert opinion says 55 al should investigated Try find Out what causing Wet insulators high-tension line might cause condition often clears up after sun burns off morning dew An S ignal should always answered ground range check before flight EVEN Continued page 134 August 1989 131 responding advertisers mention read about ModelAviation Cirrus e51/fotk2 el-land-cut quality kit includes rigging scale control setup wire parts pre-bent custom brass hardware parts individually identified pack aged Complete decals Engine sizes 45-50 FS Wings fold next fuselage full scale removal four bolts Rigging intact setup time under 3 mm owing span 55 Stand off scale $15900 VlSAeMasterCardeMoney Order Michigan residents add 4% sales tax Add $550 P&H US orders $1500 Foreign Orders Video catalog $1500 post mci VHS/Beta Regular Catalog choice Mini-Plan $300 Hand-Cut Quality Affordable Price AERODROME MODELS LTD 2623 S Miller Rd Saginaw Ml 48603 OEST 517781-3000 Other kits available Aero-Pacer Baby Pacer Curtias Jenny Flybaby Flybaby Combo Hawker Hurricane h and Jester Stack tar lessiedef Shipment ZENOAII 04237 cu laJ$26495 ZENOAH G23 56ZBNOAH 0-38 96 SACHS 26 TCA 00SACHS 32 TCA 00 SACHS 37 CDI 0SACI4S 37 TCA 00 SACHS 59 CDI 00 SACHS 58 TCA 00 Jim Meseer ERCOUPSPLANS $2396 FULL KIT $23006 JIm MeasrTOMAHAWK PLANS $2396 FULL KIT$23596 Jim Meaaer 13 KIlTEN PLANS $2996 FULL KIT $21996 FLORHO FLYER NIFTY60 kit$5296 FLORIO FLYER 40 kit $7196 FF 00 kIt 6 SUPERFLBX Gasoline tubing /ft. 20/01600 00/$3600 FLOATS 481/4 acale coma $2196 complete kit $4796 10 WW1 WHEELS $3096 P/K Spring Starter 6 PLANS SUPER STEARMAN 1/4 IGodtrayl$2600 1/3 TAYLORCRAFT 1/3 CUB Halite$3096 MGA hinted Pilot Sante 1/4 ax WWI WW2 Civ81996 Sarvo H40242 ox $1296 WoddS.ltforirge modeIa$4496 Prop sines ER TOP FLITE DYNATHRUST 20% off US Ooedme FUEL TANKS16 o $79623 OL FIBERGLASS ARROW SHAFTS 5/16 022 long 0 $1196 24 Hr Service $200 postage Bank Check MO JIM MESSERS QUALITY MODEL PRODUCTS Valley View DrIve. Box 43 Allegeny NY 14700 Radio Technique/Myers Continued page 131 AT CONTEST ground range should ex ceed 300 ft transmitter has section about 8 its antenna exposed An S gnal should grounds refusing fly channel might affected way im age 21M 31M adjacent channel looking signal outside 72-73 MHz band has strength S round should mathematics find out can interact RC transmitter produce image 21M interference wideband SC4SS receivers field has strength S M possibilities should considered Narrow-band dual-conversion receivers should able resist problems signals S low Best defense ground range checks before flight Commencement address scanner trained human brain interpret its findings just noisemaker Now have finished short course trained level beginner Go now learn use scanner find identify interference sources discover something think should added lessons let know about RC Electrics/Kopski Continued page 43 bought warranted 60 months automotive applications also war ranted half deep cycle applications latter means running down way damaging described abovejust what need peace mind during long summer flying sessions Furthermore also learned during re search subject brands warranted normal auto applicationsso watch out What Ive begun routinely now after par ticularly demanding flying session put car charge overnight ordinary house hold auto battery charger have cause routinely go flying night less summer since drives field work about 8-10 minutes length car does have chance re charge battery Folks lessons did come easily cheaply Im glad have opportunity pass info alongfor Electric other flying should fun car wont start isnt Next time have replace auto bat tery keep information mind lot flying relatively little driving consider getting inexpensive household auto-battery charger Incidentally battery brand bought Mega-Tron Speaking charging some perform ance information new Astro model 112 DC/DC Constant Current Charger item discussed June column pictured July photo shows inside view familiar previous model 102 can readily tell different Since earlier mentions Ive chance check out product bench field use First some former tested 112 high-power variable lab supply place auto battery allowed easily simulate varying conditions may found car battery same time used eight-cell 2-Ah pack 20-cell 2-Ah pack charging subjects first test run vary input voltage V0 during charge shown table below check stability 112s output current load also measured input current satisfy curiosity 8-CELL PACK20-CELL PACK volts 110 120 130 140 load amps 363 400* 432 467 amps 578 592 604 616 load amps 318 350* 385 417 amps 1175 1189 1257 1280 conclusion can drawn output current varies proportion put voltage input voltage range tested covers range very low auto battery 110 volts through nominal 120 volts up condition representative engine run ning 140 volts particularly important since auto battery voltage will dinarily change very little during given charge cycle Incidentally * notation above simply means chosen value current starters 120 volts next test charge both packs zero 112 powered constant 120volt source charge current initially set 40 amps purpose test see constant output current load would battery being charged rose terminal volt age V load throughout 15-minute charge time 8-CELL PACK20-CELL PACK Time loadVd loadVjood mmampsvoltsampsvolts 04001190400300 53781250378353 10 385 1367 378 357 15 385 1385 378 360 evaluation shows value current set start charge remains nearly setpoint during charge time period means 112 can set forget far charge current value concerned something could done un modified 102 friends name constant current comes Ive charger field use few weeks has working nicely Ive able load planes car set up charge conditions start up drive field charge planes along way have con nections auto battery rear minivan precaution take set ini tial current about 10% low cause know will rise start car enginejust shown previous table charge-while-I-drive technique new meIve doing years mod ified 102 also charge system own design Frankly its way Id accept charger cause like arrive field two three planes ready go Ive made two other observations 112 timer switch runs 13 minutes 15so Ive compensating little higher current might want time timer just make sure Also 1200-volt put maximum output current available 24-cell pack 36 amps means larger packs cannot charged preferred higher currents must charged cycle time switch must charged cars engine running evident case modified 102 another improvement 112 134 Model Aviation

George M Mye 7Radomchnque ABSTRACT How use formation ob tained scanner PREFACE In AMA position frequency co ordinator District II receive requests loan scanner AMA has assigned district usually interrogate requester find out what kind troubles being investi gated usually turns out can solved mathematically rest usually think futile monitoring effort will be cause person will monitoring doesnt know what look foror iden tify usually think futile moni toring effort will because per son will monitoring doesnt know what look foror identify flurry inspiration morning put together passed around lot peo ple comments make complete ac curate possible within scope simple handbook wanted hope will find helpful What scanner can youan overview scanner radio receiver automatically sequentially tunes list preset frequencies lets listen radio transmissions dont understand significance what hear dont learn anything get scanner district frequency coordinator tendency turn go looking voice transmissions cause can understand can find voices some frequencies shouldnt find voices 72 MHz RC channels because have channels exclusively Does mean free interference really key finding interference knowing what look look kinds radio transmissions familiar sound 55-16 MHz AM 88-108 MHz FM broadcast radio because have automobile key finding interference knowing what look forand look know about 26995-27255 MHz Citi zens Band RC channels supposed free voice interference monitor 50-54 MHz Amateur fre quencies others possible hear voice Morse code slow-scan TV packet radio bursts digital data teletype and/or digital bit-streams may AM FM PM [phase-modulatedi systems single-sideband transmttters etc think familiar sound 54890 MHz TV because have set liv ing room sound TV just soundtrack movie FM sound way vertical oscillator sput ters 60 Hz horizontal oscillator squeals 1575 kHz picture signals supersonic things 72-73 MHz MRS/PRS/ RC band carry voices such mobile tele phones also pocket pagers sometimes sound like fast telephone push-button tones sometimes sound like sleigh bells even-frequency chan nels between 10 kHz away RC channels Depending scanner designed may hear some things 108-135 MHz aircraft radio band such VOR air plane radio navigation aid low BRRRBRRRBRRR accompanied Morse code incidental transmitters com puters welding machines lightning strikes highvoltage transmission lines sometimes coro na on strongly recommend use tape recorder tool ke notebook Record sounds scanner talk recorder setting up tests ad justing scanners controls point Im making lot hear Identification interpretation what hear important hearing article will help teach yourself interpret some what hear Since aural experience strongly rec ommend use tape recorder tool learn ing Use like notebook Record sounds scanner talk recorder setting up tests adjusting scanners controls could make such tape work wont thinking wont learn anything Lesson #1 sounds RC systems else failsREAD THE BOOK will tell turn scanner make its tricks Bill Hershberger has written manual interprets Japanese techno-speak sim ple English sketches control locations added manual should available AMAs scanners time published Recess read Bills manual Welcome back Now lets discover differ ence between sound AM FM FM/ PCM turning various RC sets listen ing scanner will quickly learn tell difference between simple twoor three-channel AM set complex multichannel FM/PCM RC system just listening Lesson #2 Signal strengths squelch controls have go outdoors lesson good procedure have someone walk down road operating RC transmitter listen scanner work scanners controls get best results will learn lot about squelch control af fects what hear will also learn about dropouts transmitter scanner whip antennas held vertically 13 ft transmitter moves away scanner signal will drop minimum' best once road doesnt have electric wires poles alongside sec ond time road does makes differ ence ground suspended electric wires overhead continuous metal fence nearby buried wires pipes below join sig nal transmitter scanners tenna probably wont hear anything after transmitter one-half mile away scanner Keep track signal strength S meter reading function distance transmitter Plot signal strength versus distance will also learn about dropouts transmitter scanner whip antennas held vertically will observe 13 ft transmitter moves away scanner signal will drop minimum Dropouts close transmitter noticeable between dropouts signal will peak maximum Observe variations S meter Put scanner antenna horizontal point operating RC transmitter itend onfrom about 150 ft away Note signal strength 5 meter Have person holding trans mitter slowly rotate tip-on-the-ground position vertical position watch S meter signal should rise maxi mum transmitter antenna inclined about 45 0 fall new minimum 900 vertical Have person transmitter hold ver tical high over head possible Ob serve effects S~ meter Write down S meter indications versus antenna angle few data points plot yourself curve 38 Model Aviation 70 Froehlkh Farm Rd Hkksville NY 11901 What can learn scanner Pre tend months column book Table Contents Preface What scanner can youan over view Lesson #1 sounds RC systems Lesson #2 Signal strengths squelch controls Lesson #3 sounds adjacent channels Lesson #4 Third-order intermodulation Lesson #5 Other sounds intermodulation a First orderdirect interference b 21MThe 23-channel problem c ImageThe 455-channel problem Lesson #6 much stuff really interference Commencement address .. dont understand sig nificance what hear wont learn anything have learned something about effects tenna orientations height Overall will develop some understanding dynamic range signals could fly over about 20 ft would hear dropouts caused phase cancellation relates fact radio signals travel faster air ground exact speed difference affected moisture soil phase cancellation effects cause var iable Ordinarily will show up changes ground range test distances difference tween ground range measured over freshly watered golf course compared over dry sand can significant Sensitive airplanes may glitch ie lose con trol momentarily result dropouts causes airplanes usually fly through dropouts quickly go unno ticed Helicopters other hand might unlucky try hover dropout region should tell something about hovering along altitude some distance transmit ter PCM helps overcome dropouts .. pair transmitters 23 channels apart might affect wideband SC455 air regard what RC channels on #3 sounds adjacent channels Set scanner 72680 MHz set up transmit ter RC44 shouldnt hear anything unless RC transmitter too close Move RC transmitter slowly 3 ft away 100 ft away Note signal changes scan ner has wideband/narrow-band switch once switch position note results What hearing similar what receiver hears adjacent MRS/PRS channelwhich transmitters located between 10 kHz away RC channels Note 5 meter reacts Scan 7200 through 7300 MHz may observe strong signal can heard three channels sequence eg PR5375 72540 MHz RC38 72550 MHz PR5385 72560 MHz wideband transmitter leaking onto adjacent channels 10 kHz awayadjacent channel interference defi nition Lesson #4 Third-order intermodulation easy since 31M signals generated RC transmitters always exactly centered RC channels can always heard scanner Put scanner 72590 MHz RC4O leave Set up operating RC44 transmit ter 100 ft away scanner Have another club member stand about 3 ft RC44 transmitter turn RC42 transmitter should hearing 31M RC4O Scan slowly 7200 7300 MHz looking other signals should find 31M 72650 727 10 MHz Note loud record signal strength 5 units Stop scanner see 31M sound goes away transmitters turned off have transmitter available chan nel 31M put transmitter op eration see far away can taken before 31M can heard learning about relative signal strengths Turn several transmittersthree four five six moreat same time sequence Space 30 ft apart line per pendicular line scanner Scan World S t best sellfl9 Spark lgfltt0O Systemi V Oiasen Byron 0riuhds TEtG Mfg uid kM Aircraft Sqiply tar its outstuuhlg ralility Complete single cylinder system including throttlecoupled spark advance kit spark spark plug lead25 plug battery pack charger 900 sh elded Much huger onpue lie Easy huid stals-no kickback 1-12D90 RPM rabble hUe 0% nore power tear strokers om histabtion avielile Slielded spat pleg lead mel 9W ph cover Lower waded FummyenpiesUitmp2&4stroke siqeaidtwhicyhders zolpouhictsavddale Smut cob gawk phiw dieldal pha lead B Ihckw kits avale B&P Associates Gives Total Flight Line FREEDOM battery needs call write B&P Associates PO Box 22054 Waco TX 76702-2054 817662-5587 new electric starter battery pack cuts cord has always tied starter power panel Discover freedom being able start plane wherever added safety less wire get caught prop charge hefty 4 Amp/hour pack will take through weekend flying power enough spare dont stop have Ni-Cads virtually size imaginable cut experimenter free design whatever takes make yours best setup field August 1989 39 72 73 MHz smallest available steps squelch control turned way down CCW helps AM transmitters FM transmitters PCM trans mitters mix sounds differ ent doesnt now should able tell what transmitter types making up intermodulation package just listening get ting education Now turn off transmitters except two Put butt-to-butt Scan 7200 7300 MHz Notice anything familiar Two transmit ters butt-to-butt sound like bunch transmit ters physically separated dont Thats call arrangement Flight Line Simulation test setup rule 31M Any two transmitters will generate 31M frequency midway between operating frequencies far above below frequencies separated frequency Somebody has access spectrum ana lyzer will tell 31M signals about 30 dB below transmitter signalwhich true Other people familiar properties RC receivers will tell interference oc curs spurious signal received 15 22 dB below received control transmitter signal Note means weak signal interferes control strong signal difference signal strengths 8 15 dB margin safety 3lM interferenceall things being equal studies signal strengths dropouts will have convinced things never equal Signal strength drops rapidly distance control transmitter increases drop Outs lower transmitters usual signal 15 dB easily demonstrated changes relative antenna positionsas have seen yourself should able have opinion about what people tell some 31M examples 1 RC30 RC4O will generate 31M RC2O RC35 RC5O 2 TV4 sound carrier 7175 MHz RCl3 can produce 31M RC28 other TV4 combinations like RCl8 RC38 RC23 RC48 RC28 dumps 31M both RCl3 RC58 strength TV4 signal determines whether resulting 31M will bother anybody have access Kraft synthesizer transmitter can easily check situation Out Remem ber write down signal strength 5 un its will use information Lesson #6 suspect channels RCl3 18 20 21 23 28 38 48 58 presence strong S 4 signal measured flight line Note RCl3 RC2l will new considerations 1991 dont have strong TV4 signal area may have something else like TV5 microwave beams Microwave beams very narrow likely affect plane particular spots sky may able hear scanner tow ers easy spot tiny dishes pointing parallel ground can take list frequencies work out combinations own based what find have evaluate whether 31M signals strong enough con sidered interference Lesson #6 somewhat limited assessment fact scanner ground doesnt hear much does airplane receiver air Lesson #5 Other sounds intermodulation First easy Turn two RC4O trans mitters same channel same time Set scanner channel listen first transmitter both should hear super heterodyne whistle among other things come second transmitter Thats First Order Intermodulation Pretty loud isnt can hear scanner happens b Now difficult problem interferences generated inside receivers cant hear because scanner receiver differ ent RC receiver have find some thing apply some reasoning some math ematics earn pay DFC lesson must have pencil paper page 10 Membership Manual ad dition scanner tape recorder 21M 23rd-channel problem rule 21M Take operating fre quency transmitter add subtract TRAINERFOAMAIREMONARCH SPAN 10$IA 095 SPAN 74SPAN 10 WEIGHT 2 lbs WEIGHT 65-75 lbs $O95 WEIGHT 2 lbs $164 POWER 0 00$IAgs POWER 0POWER 0 cc 3 4 CHANNEL4CHu1-IFOUR CHANNELFOUR CHANNEL CALL OR WRITE FOR FREE INFOART 1 NEODESHA KS 66757 ON SAC KITS AND QUADRA PRICES,./-Ij316 325-2821 FREE SHIPPING ON KIT ORDERVISA / MASTERCARD ACCEPTED 40 Model Aviation OPSorYS parts close 1-800-535-2568 Dealer Inquiries Invited SThe Part Cm*ea~% 9miai4 9#ce BIRCH PLY WOOD 1/64o12o12/7s1/40601274 1/640120243501/4012012146 1/640120497001/4012024293 1/64 0 46 0 4626001/4 0 12046565 BALSA WOOD STICKS 1/16-INCH3646 1116 111606 1/1603/3207 1/1601/60811 1/16o3/160913 1/160 1/41015 1/1603181217 1/160 1/21620 1/1603/42126 3/32-INCH3646 3/3203/320611 3/32 0 1/60913 3/32 03/161015 3/320 1/41316 3/32s3/81419 3/320 1/21621 3/32 0 3/42431 Double Balsa Wood Prices Spruce Basswood Sticks 1/6-INCH3646 3/8-INCH3646 2737 1/80 1/60811 1/Bo3/161119 1/60 1/41317 1/6 3/61621 1/60 1/21724 1/603/42523 3/I 6-INCH3646 3/1603/161317 3/16 1/41419 3/16s3/61621 3/160 1/21625 3/16 3/42636 1/4-INCH3646 1/4 1/41621 1/403/61625 1/40 1/22129 1/4 0 3/43142 5/16-INCH3646 5/16 9/162027 5/16 0 3/82230 9/160 1/22736 9/16 0 3/43952 3/6 0 3/6 3/60 1/23041 3/6 0 3/44460 1/2-INCH3646 1/2 0 1/23749 1/203/45270 TRIANGULAR CUT BALSA 1/401/403624 3/903/603629 1/201/203637 3/4o3/4o3647 10103661 BALSA PLANKS 3/403036176 102036164 1o3o36230 104036303 202036230 203036329 204036464 303036490 304036690 BALSA SHEETS I-INCH3646 1/160 I2736 3/32 0 13040 1/8013344 3/16 0 13749 1/4 0 14157 3/6 0 I6372 1/2 0 16999 2-INCH3646 1/32023040 1/16023646 3/32 0 24154 1/6024660 3/16025472 1/4026364 3/60277103 1/202113150 3-INCH3646 1/32034053 1/16034356 3/32 0 36270 1/6036090 3/16 037290 1/40364112 5/1603103134 3/603120160 1/203160200 4-INCH3646 1/32046597 1/160473101 3/320462109 1/60495126 3/1604114151 1/404131193 3/604162271 1/204219325 1/320601252 1/320120 12105 1/32 012o 24210 1/32012048420 1/15o6o1252 1/ISo12012105 1/15012024210 1/16012046420 3/320501261 3/32o12012163 3/32 0/2o24326 3/32 012046652 1/6o6o1299 1/90120 12179 1/So12024356 1/6 o12 0 40712 3/160601274 3/16012012146 3/15012024253 3/16012046565 Superior Aircraft Materials 3/80120 12160 3/6 o12 0 24360 3/6 o12 046720 1/20 120 12202 1/2 0 12o 24405 1/2o12o49606 LITE PLYWOOD 1/6o12o1256 1/9 0 12o24112 1/6012049224 TAPERED TRAILING EDGE3646 1/60 1/22230 3/16 0 3/42940 1/40 14255 5/16014461 3/60 15272 12020-G Centralia iian Gardens California 90716 865-3220 Handling Charge-$500 $300 COD mum Order $2000 FOB Factory accept Personal checka COD fornia Residents add 6% Sales Tax receivers intermediate frequency find po tential interferer common intermediate frequency 455 kHz 455 MHz Narrow-band SC455s less likely af fected 21M wideband SC4SSs SC le-conversion Thats because possible 21M interferers S kHz away RC channel narrow-band receiver can ig nore Narrow-band SC4SSs becoming available Lets say find something 72500 MHz Add 455 get 72955 MHz closest RC channel RC58 72950 MHz 5 kHz away might produce interference RCS8 receiver signal 72500 has strength S C455 receiver wideband Something worse pair transmitters pair 23 channels apart might affect wideband 5C455 air regard what RC channels Its matter relative signal strengths general wary signal over -5 dBM easiest way evaluate test field airplane Let airplane ground tell disturbed doing ground range test noticing whether distance shorter usual arent finished yet Now look oppo site direction 72500 72045 closest RC channel 72050 MHz Again might suffer interference RC58 didnt best test field test Heres 21M example find FM sound TV4 71750 MHz has signal strength -4 dBm 2 Looking upscale 71750 72205 MHz between RC2O RC2I closer RC2I Because FM sound fre quency wobbles bit isnt exactly 7175 MHz times So might get hit either chan nel course manufacturers know expect will put local oscillator channels above transmitter because way local oscillators defined para graph 410 AMA Radio Control Utiliza tion Plan page 11 column 1988 Mem bership Manual have avoid simultaneous flying RC43 RC44 high-band channels will have check out TVS paragraph 410 AMA Radio Control Utilization Plan page II 1988 Member ship Manual changed put local oscillators outside 72 MHz band thereby minimizing 21M between modelers intermodulations TV4 TVS can problem best lution might stay off RC2O RC2 1 alto gether insist flying 5C455 re ceiver presence strong S 4 signal However 21M isnt confined SC455s Any receiver can affected 21M case dual-conversion receivers first conversion usually has local oscillator 1155 MHz away control transmitter much off set front end usually can attenuate potential 21M signal insignificance So doubt owners dual-conversion RC receivers have reason worry about 21M Yes 21M between modelers wont become problem until 199 Iand 50 chan nels sanctioned planned oddnumbered RC channels create problem cause pair transmitters 23 channels apart can cause difficulty Using even-number ed channelsas doing right nowthere no problem already have MRS/PRS transmitters separated RC channels amount can expressed 22 RC channels plus 10 kHz example would relative RCI6 16 lus 10 kHz RC36 plus 10 kHz just likely generate 21M existing 5C455 Rx RC channels 23 numbers away complaints received various locations around country LA Denver Atlantic City seems doing depends sig nal strength flying field So have find MRS/PRS transmitters consider what capable doing c image frequency Any receiver sub ject image interference practical stand point SC455sonRCll 12 13 14 57 58 59 60 have anything worry about Continued page 131 August 1989 41 TAIBI PRESENTI FLINGER THE ULTIMATE SMALL SAILPLANE HANDLAUNCH HI-STARTorSLOPE WINGSPAN 57 WEIGHT l2oz MACHINE CUT PARTS DEALERS&DIST INOUIRIES INVITEDFLINGER LJMP 110 $2995 ELECTRA L ITE-ICARUS-PANTERA- METEOR-ELECTR ICUS-WHISTLER PRELUDE-COMET LARRY JOLLY MODEL PRODUCTS 5501 W COMO SANTA ANA CALIFORNIA 92703 714 826 6861 Letters Editor Continued page 11 Ni-Cds dont seem affected cold anything like alkaline cells Once problem corrected lit tle Nickle flew flawlessly greatest small three-channel airplanes have ever flown James Harris Marion OH Safety/Preston Continued page 22 fit inside muffler between bolt holes will stop two halves warping have done three G-38s havent problems mufflers coming loose Now respect firewall fire picture column builders Giant aircraft would use engine mounts made engines flat plates come would have air gap behind muffler cool ing gasoline engines run hot dont think put hand hot muffler like did five years ago Thanks have taken time write describe mishaps Without letters would no Safety column wish another safe month Sweepee/DhaII Continued page 37 wont take off until its ready airplanes slow speed flying characteristics indicated also peculiar com ing out near hover increase throttle gradually ease off elevator stick using little down control get some extra speed Try maneuvers safe al titudes beginning youre getting used airplanes foibles might also find need get acquainted its strange appearance air before attempt ing anything too fancy color scheme clearly distinguishes front plane back should come handy low throttle condition flight charac teristics model similar sport airplane until force high angle attack slow speeds gradually increas ing up control seems have little effect airplanes attitudebut does bring model virtual halt point sink rate will high probably will have keep rudder control active keep course However plane shows relatively little tendency stall out condition Im still exploring full range SAFE FLYING IS NO ACCIDENT airplanes flight characteristics Join search Discover Sweepee yourselfand happy backward flying Radio Technique/Myers Continued page 41 must wary transmitters 910 MHz 455 channels away Such transmitters MRS/PRS transmitters find strong signals S SlO5 115 125 135 145 565 575 585 595 605 have consider potential interferences xx5 shorthand code PRS channel 10 kHz above RC channel number given Channel 105 0 MHz Image example strong signal S und 72040 PRS 125 may interfere 5C455 receiver channel 125 RC58 summary find something scan ner note its frequency some mathemat ics see what found might problem Lesson #6 much stuff really inter ference looking signal 72xxx MHz has strength 55 nd can expect signal adjacent channel problem wideband receivers air Expert opinion says 55 al should investigated Try find Out what causing Wet insulators high-tension line might cause condition often clears up after sun burns off morning dew An S ignal should always answered ground range check before flight EVEN Continued page 134 August 1989 131 responding advertisers mention read about ModelAviation Cirrus e51/fotk2 el-land-cut quality kit includes rigging scale control setup wire parts pre-bent custom brass hardware parts individually identified pack aged Complete decals Engine sizes 45-50 FS Wings fold next fuselage full scale removal four bolts Rigging intact setup time under 3 mm owing span 55 Stand off scale $15900 VlSAeMasterCardeMoney Order Michigan residents add 4% sales tax Add $550 P&H US orders $1500 Foreign Orders Video catalog $1500 post mci VHS/Beta Regular Catalog choice Mini-Plan $300 Hand-Cut Quality Affordable Price AERODROME MODELS LTD 2623 S Miller Rd Saginaw Ml 48603 OEST 517781-3000 Other kits available Aero-Pacer Baby Pacer Curtias Jenny Flybaby Flybaby Combo Hawker Hurricane h and Jester Stack tar lessiedef Shipment ZENOAII 04237 cu laJ$26495 ZENOAH G23 56ZBNOAH 0-38 96 SACHS 26 TCA 00SACHS 32 TCA 00 SACHS 37 CDI 0SACI4S 37 TCA 00 SACHS 59 CDI 00 SACHS 58 TCA 00 Jim Meseer ERCOUPSPLANS $2396 FULL KIT $23006 JIm MeasrTOMAHAWK PLANS $2396 FULL KIT$23596 Jim Meaaer 13 KIlTEN PLANS $2996 FULL KIT $21996 FLORHO FLYER NIFTY60 kit$5296 FLORIO FLYER 40 kit $7196 FF 00 kIt 6 SUPERFLBX Gasoline tubing /ft. 20/01600 00/$3600 FLOATS 481/4 acale coma $2196 complete kit $4796 10 WW1 WHEELS $3096 P/K Spring Starter 6 PLANS SUPER STEARMAN 1/4 IGodtrayl$2600 1/3 TAYLORCRAFT 1/3 CUB Halite$3096 MGA hinted Pilot Sante 1/4 ax WWI WW2 Civ81996 Sarvo H40242 ox $1296 WoddS.ltforirge modeIa$4496 Prop sines ER TOP FLITE DYNATHRUST 20% off US Ooedme FUEL TANKS16 o $79623 OL FIBERGLASS ARROW SHAFTS 5/16 022 long 0 $1196 24 Hr Service $200 postage Bank Check MO JIM MESSERS QUALITY MODEL PRODUCTS Valley View DrIve. Box 43 Allegeny NY 14700 Radio Technique/Myers Continued page 131 AT CONTEST ground range should ex ceed 300 ft transmitter has section about 8 its antenna exposed An S gnal should grounds refusing fly channel might affected way im age 21M 31M adjacent channel looking signal outside 72-73 MHz band has strength S round should mathematics find out can interact RC transmitter produce image 21M interference wideband SC4SS receivers field has strength S M possibilities should considered Narrow-band dual-conversion receivers should able resist problems signals S low Best defense ground range checks before flight Commencement address scanner trained human brain interpret its findings just noisemaker Now have finished short course trained level beginner Go now learn use scanner find identify interference sources discover something think should added lessons let know about RC Electrics/Kopski Continued page 43 bought warranted 60 months automotive applications also war ranted half deep cycle applications latter means running down way damaging described abovejust what need peace mind during long summer flying sessions Furthermore also learned during re search subject brands warranted normal auto applicationsso watch out What Ive begun routinely now after par ticularly demanding flying session put car charge overnight ordinary house hold auto battery charger have cause routinely go flying night less summer since drives field work about 8-10 minutes length car does have chance re charge battery Folks lessons did come easily cheaply Im glad have opportunity pass info alongfor Electric other flying should fun car wont start isnt Next time have replace auto bat tery keep information mind lot flying relatively little driving consider getting inexpensive household auto-battery charger Incidentally battery brand bought Mega-Tron Speaking charging some perform ance information new Astro model 112 DC/DC Constant Current Charger item discussed June column pictured July photo shows inside view familiar previous model 102 can readily tell different Since earlier mentions Ive chance check out product bench field use First some former tested 112 high-power variable lab supply place auto battery allowed easily simulate varying conditions may found car battery same time used eight-cell 2-Ah pack 20-cell 2-Ah pack charging subjects first test run vary input voltage V0 during charge shown table below check stability 112s output current load also measured input current satisfy curiosity 8-CELL PACK20-CELL PACK volts 110 120 130 140 load amps 363 400* 432 467 amps 578 592 604 616 load amps 318 350* 385 417 amps 1175 1189 1257 1280 conclusion can drawn output current varies proportion put voltage input voltage range tested covers range very low auto battery 110 volts through nominal 120 volts up condition representative engine run ning 140 volts particularly important since auto battery voltage will dinarily change very little during given charge cycle Incidentally * notation above simply means chosen value current starters 120 volts next test charge both packs zero 112 powered constant 120volt source charge current initially set 40 amps purpose test see constant output current load would battery being charged rose terminal volt age V load throughout 15-minute charge time 8-CELL PACK20-CELL PACK Time loadVd loadVjood mmampsvoltsampsvolts 04001190400300 53781250378353 10 385 1367 378 357 15 385 1385 378 360 evaluation shows value current set start charge remains nearly setpoint during charge time period means 112 can set forget far charge current value concerned something could done un modified 102 friends name constant current comes Ive charger field use few weeks has working nicely Ive able load planes car set up charge conditions start up drive field charge planes along way have con nections auto battery rear minivan precaution take set ini tial current about 10% low cause know will rise start car enginejust shown previous table charge-while-I-drive technique new meIve doing years mod ified 102 also charge system own design Frankly its way Id accept charger cause like arrive field two three planes ready go Ive made two other observations 112 timer switch runs 13 minutes 15so Ive compensating little higher current might want time timer just make sure Also 1200-volt put maximum output current available 24-cell pack 36 amps means larger packs cannot charged preferred higher currents must charged cycle time switch must charged cars engine running evident case modified 102 another improvement 112 134 Model Aviation