AN Interference Meter Its always gratifying discover someone reads acts upon advice given column So pleased see article October issue Sun beam newsletter West Orange Sunfliers Radio Control Club Inc John L Thomas II editor Orlando Florida newsletter sent AMA HQ article Jack Minch showing picked up discussion use ammeterOct 79 MA pg 21 extended Jack puts female Deans connector switch harness lead receiver Fig 1 shorts pins male plug together place circuit restored new Mr Minch obtains another male Deans plug wired ammeter way can use meter variety RC systems expense separate aileron extender cable Depending different kinds systems have could considerable saving disadvantage purposes would have modify someone elses system order make use meter Nonetheless Jack Minch tried ammeter found some problems didnt realize sat down write long article describing findings newsletter editor Speaking newsletter editors everywhere go thou likewise myself thanks Jack Minch crediting Radio Technique giving idea Recently wanted put movie camera plane use towing sailplanes get look things act high up pilots ground have go faith intuition seemed like good idea check interference problems ground found need interference meter Reasoning kind interference really interested kind moves servos whipped out trusty surprise ammeter initial test setup pretty fundamentaL took sophisticated flight pack available Futaba Contest 7 hooked together workbench ammeter inserted between flight battery pack its switch harness Transmitter turned antenna collapsed put far enough away just extreme ground range distance took movie camera film put close receiver ran Before starting movie camera ammeter read very normal 05 amps turned movie camera current jumped over 1 amp stayed Interestingly trans mitter still control servos Moving camera around setup didnt change results much seemed some interfer ence problems Apparently motor movie camera making some kind electrical noise got through metal case receiver showed up servos lot extra pulses servos werent fast enuugh follow noise around tried hard could explanation high current drain least can said situation minute camera time would drain about 6 minutes flight time out batteries addition power required fly mission roll film would cut 20 minutes out charge addition noise would keep AGC line down reducing receivers sensitivity making loss control lot likely must say very favor ably impressed Futabas ability keep right controlling situation face such extreme interference get something extra pay triple-tuned front end 3-can 107 MHz IF strip its crystal18 Model Aviation 1-1g Z test set-up riece tape holds camera switch engaged ammeter shows interference causes current idle transmitter over 1 amp build up ter George did Oct 79 MA can save money using box came meter case also epoxied reversing switch foam accommodate both charging dis charging measurements octopus tangle aileron extension wired parallel controlled mixer course plus additional 4can 455 KHz IF strip another crystalcontrolled mixer looks like two complete receivers board fact Just check turned transmitter ott servos shivered lot current stayed around 75 amps got interest might expect repeated test some other systems Rather bore data see Fig 3 good test worth thousand expert opinions Rhiele Axiom sure didnt expect results got Let divert moment some other mail AMA HQ An Open Letter Lee Taylor editor Quarter-Scale Assoc America Newsletter AMA 75150 parties concemed proposals FCC additional RC frequencies strong plea made permission use FM based experiences Major Bob Jacquot living Germany Major Jacquot frustrated attempt fly Quadra-powered J-3 Cub model loaded clattering metal-to-metal joints clatter seriously interfered AM radio use after consultations experts advised him put safe place like museum Bob made attempt European FM set time has completed year satisfactory flying model Which brings up Myers Corollary Rhiele Axiom Dont guesstest Before leaving idea FM sure cure RF interference sure heck isnt Id like know about situa tion Major Jacquot read please send few details about new radio Wed particularly like know what RF channel used what type decoder ratio detector discriminator quadrature type whatever Ill see information gets passed along Lots quarter-scale operators have similar problems Still subject interference bit recently tuning up radio system transmitter placed center large field walked out plane until loss control encountered got Out handy tuning wand began adjusting IF slugs Pretty soon ground range double what started system started hopping around Since close Grumman Aerospace Corp Electronic Systems Center seemed likely smart jammer being tested latched onto RF signal test hypothesis turned off transmitter turned back again few moments control before system went business itself Oh well time supper anyway waited till sufficient time late shift have punched out went back tuning put transmitter wifes oven could adjust attenuation ofthe signal varying amount door open went back work hunting started again beginning suspect transmitter might fault got out oscilloscope demodulator probe transmitter fine Whats next guess George logical thing disconnect servos time see fault werent Whats left Either receiver batteries just charged batteries must receiver Put oscilloscope see pulses hopping around like rabbits spring Turn off transmitter see nothing absolutely nothing makes no sense because should looking interfering signal Well put scope battery line see theres noise Hmmm 36 volts Substitute fresh pack problem goes away about interference turns out dead cell flight pack course drop dead right middle tuning session What else new Well guys hope youve got message can measure interference simple instruments oscilloscope wasnt necessary Going back movie camera story would use test results comparison-shoppers guide better radios test shows sensitivity kind RF noise others However want use movie camera airplane have suggestion Wrap aluminum foiL did found could rub running movie camera over systems tested twitched foil kept noise inside package Keep letters coming Most get answered eventually Some become theme column answered way havent got answer keep watching column may find pleasant surprise February 1980 19 FI MVFR MA1JIF~AMERA TEST FOR INTERFERENCE SENSITIVITY OF RF SYST George M Myers 70 Froehlich Farm Rd Hicks iille NY 11801 Fig 4 camera installation before George wrapped camera aluminum foil package noise nylon 4-20 bolt through wing screws cameras tripod socket insure camera stays plane
Edition: Model Aviation - 1980/02
Page Numbers: 18, 19
AN Interference Meter Its always gratifying discover someone reads acts upon advice given column So pleased see article October issue Sun beam newsletter West Orange Sunfliers Radio Control Club Inc John L Thomas II editor Orlando Florida newsletter sent AMA HQ article Jack Minch showing picked up discussion use ammeterOct 79 MA pg 21 extended Jack puts female Deans connector switch harness lead receiver Fig 1 shorts pins male plug together place circuit restored new Mr Minch obtains another male Deans plug wired ammeter way can use meter variety RC systems expense separate aileron extender cable Depending different kinds systems have could considerable saving disadvantage purposes would have modify someone elses system order make use meter Nonetheless Jack Minch tried ammeter found some problems didnt realize sat down write long article describing findings newsletter editor Speaking newsletter editors everywhere go thou likewise myself thanks Jack Minch crediting Radio Technique giving idea Recently wanted put movie camera plane use towing sailplanes get look things act high up pilots ground have go faith intuition seemed like good idea check interference problems ground found need interference meter Reasoning kind interference really interested kind moves servos whipped out trusty surprise ammeter initial test setup pretty fundamentaL took sophisticated flight pack available Futaba Contest 7 hooked together workbench ammeter inserted between flight battery pack its switch harness Transmitter turned antenna collapsed put far enough away just extreme ground range distance took movie camera film put close receiver ran Before starting movie camera ammeter read very normal 05 amps turned movie camera current jumped over 1 amp stayed Interestingly trans mitter still control servos Moving camera around setup didnt change results much seemed some interfer ence problems Apparently motor movie camera making some kind electrical noise got through metal case receiver showed up servos lot extra pulses servos werent fast enuugh follow noise around tried hard could explanation high current drain least can said situation minute camera time would drain about 6 minutes flight time out batteries addition power required fly mission roll film would cut 20 minutes out charge addition noise would keep AGC line down reducing receivers sensitivity making loss control lot likely must say very favor ably impressed Futabas ability keep right controlling situation face such extreme interference get something extra pay triple-tuned front end 3-can 107 MHz IF strip its crystal18 Model Aviation 1-1g Z test set-up riece tape holds camera switch engaged ammeter shows interference causes current idle transmitter over 1 amp build up ter George did Oct 79 MA can save money using box came meter case also epoxied reversing switch foam accommodate both charging dis charging measurements octopus tangle aileron extension wired parallel controlled mixer course plus additional 4can 455 KHz IF strip another crystalcontrolled mixer looks like two complete receivers board fact Just check turned transmitter ott servos shivered lot current stayed around 75 amps got interest might expect repeated test some other systems Rather bore data see Fig 3 good test worth thousand expert opinions Rhiele Axiom sure didnt expect results got Let divert moment some other mail AMA HQ An Open Letter Lee Taylor editor Quarter-Scale Assoc America Newsletter AMA 75150 parties concemed proposals FCC additional RC frequencies strong plea made permission use FM based experiences Major Bob Jacquot living Germany Major Jacquot frustrated attempt fly Quadra-powered J-3 Cub model loaded clattering metal-to-metal joints clatter seriously interfered AM radio use after consultations experts advised him put safe place like museum Bob made attempt European FM set time has completed year satisfactory flying model Which brings up Myers Corollary Rhiele Axiom Dont guesstest Before leaving idea FM sure cure RF interference sure heck isnt Id like know about situa tion Major Jacquot read please send few details about new radio Wed particularly like know what RF channel used what type decoder ratio detector discriminator quadrature type whatever Ill see information gets passed along Lots quarter-scale operators have similar problems Still subject interference bit recently tuning up radio system transmitter placed center large field walked out plane until loss control encountered got Out handy tuning wand began adjusting IF slugs Pretty soon ground range double what started system started hopping around Since close Grumman Aerospace Corp Electronic Systems Center seemed likely smart jammer being tested latched onto RF signal test hypothesis turned off transmitter turned back again few moments control before system went business itself Oh well time supper anyway waited till sufficient time late shift have punched out went back tuning put transmitter wifes oven could adjust attenuation ofthe signal varying amount door open went back work hunting started again beginning suspect transmitter might fault got out oscilloscope demodulator probe transmitter fine Whats next guess George logical thing disconnect servos time see fault werent Whats left Either receiver batteries just charged batteries must receiver Put oscilloscope see pulses hopping around like rabbits spring Turn off transmitter see nothing absolutely nothing makes no sense because should looking interfering signal Well put scope battery line see theres noise Hmmm 36 volts Substitute fresh pack problem goes away about interference turns out dead cell flight pack course drop dead right middle tuning session What else new Well guys hope youve got message can measure interference simple instruments oscilloscope wasnt necessary Going back movie camera story would use test results comparison-shoppers guide better radios test shows sensitivity kind RF noise others However want use movie camera airplane have suggestion Wrap aluminum foiL did found could rub running movie camera over systems tested twitched foil kept noise inside package Keep letters coming Most get answered eventually Some become theme column answered way havent got answer keep watching column may find pleasant surprise February 1980 19 FI MVFR MA1JIF~AMERA TEST FOR INTERFERENCE SENSITIVITY OF RF SYST George M Myers 70 Froehlich Farm Rd Hicks iille NY 11801 Fig 4 camera installation before George wrapped camera aluminum foil package noise nylon 4-20 bolt through wing screws cameras tripod socket insure camera stays plane