a loec ni ue George M Myers INTERFERENCE Now have new RC channels everyone worried about interference commercial transmitters might ex ample ask District Frequency Coordinator about such transmitters near flying site might point out data supplied AMA HQ Common Carrier transmitter rated 25 Watts looking through 1400 beam antnna mounted 300-ft-high tower time panic antenna 10 miles flying site First have know power output transmitter Either manufacturer will tell wont wont break line transmitter battery pack ON/OFF switch install milliammeter should have full-scale value 250 mA Read current transmitter operating normally antenna extended unplug crystal RF module read again difference multiplied battery voltage power input RF section 50% reasonable esti mate RF section efficiency take half input power being power output can expect find value somewhere between 1/4 Watt 250 mW 750 mW 72 MHz transmitter Since know received power drops off square distance between transmitter receiver can calculate maximum safe altitude fly formula h2 — PG N2P2G2 Whereh N P1 P2 maximum safe altitude miles number miles interferer Your transmitters output Watts Your antenna gain number Interferer transmitter output Watts His antenna gain number lving h2 substituting h2N2P1G1102x300x1 _ 30 P2G225x5 h 49 example 1 have substituted 300 Watts transmitter since representative older transmitters some new ones have assigned gain 5 interferers beam antenna advice friend Duffy Galle gro electronics engineer antenna specialist Duffy helped learn enough write column Taking square root cal culator find h 049 miles 049 mi X 5280 ft per mi ft should adequate purposes calculation assumes two things receiver responds equally well control signal interference typical wideband receiver exposed Com mon Carrier transmitter 10 KHz away 2 interfering transmitter located high enough can see over curve AMA SAFETY CODE TEST 100400 1000 AIRPLANE OR TOWER HEIGHT FEET 40 Model Aviation 1000 Co w -J z 0 N 0 0 10 1 310 10000 can use graph find distance radio horizon high-frequency transmission Please note scales both logarithmic month George gives relatively painless quick way check potential radio interferences coming new age RC new channels available now near future will become vital George ran series tests new Tower 500 radio see resistant adjacentchannel interference results interesting can same other systems gather information club Note antennas held horizontally parallel other Control signal transmitter tuned aircraft system Walk Out until reach limit reliable ground range keep cycling channel George used rudder walk towards model interference transmitter until starts causing control glitches model Since interested relative distances between plane two transmitters can just pace oft distance record earth airplane practical fact VHF radio waves travel straight lines radio horizon transmitter conforms Figure same true receiver radius intluence extends distance equal sum interfering transmitters radio hor izon receivers radio horizon num ber case 15 plus 40 55 miles influence certainly can felt 10 miles Due its antenna height other transmitter can see planes parked flight line something consider cause transmitters power low enough can fly up 2500 feet xour transmitter before interferencc sets Lets move other transmitter little closer say mile field see what happens h 049mi 125 049 x 5280 ft think defines field suitable Helicopters marginally theyre using wideband receivers As can see its simple calculation can quickly made cheap pocket calculator anyone should need Some interferences can happen right field Jack Albrecht National Sales Manager Kraft Systems Frequency Committee member preparing Phase-In plan has pointed out certain new channels IS KHz High Side local oscillator frequency old channels combinations 72081RC38 72 l6/RC42 7224/RC46 72 32/RC5O 7240/RC54 converted wideband receiver new channel non-converted wideband receiver old system interference might occur flying same flight line does occur have pairs share same frequency pin clipboard send one-half pair fly nearby field isnt such bad idea can work channel-splitting another club Once split guys will better off some folks other channels An Adjacent-Channel Interference Test started idea 72 MHz 010 MEASURED RESPONSE dB 203040 RC4O/RC3 / 7208/RC54 7208/RC38 RC4O/7240 LD RC CH NNEL 2/7208 RC5i NE /RC54 RC CHAN tEL WORST CASE ESTIMATED RESPONSE COMMON CARRIER 10KHZ OFFSET transmitters radiate approximately same power worked simple No Tools technique might use assess adjacent-channel sensitivity RC receiver Lets begin test plan show data developed use assess interference potential Common Carrier transmitters 10 KHz away new RC channels Test Plan Test Objective Determine Distance Ratio interference equal-power adjacent-channel transmitters Test Setup Receiver sy m non metallic support 2 Signal Transmitter maxtmum range control non-metallic support 3 Interfering Transmitter maximum range interfere control non-metallic support 4 antennas horizontal parallel mounted three feet above ground Test Procedure Verify Signal Transmitter Receiver same frequency ON 2 Verify interferer adjacent channel OFF 3 Walk Signal Transmitter out maximum range control count record paces Receiver keep cycling rudder control 4 Turn Interfering Transmitter ON walk Interferer out maximum distance between Interfering Transmitter Receiver will interfere control record distance Receiver 5 Tum Interferer OFF verify control Signal Transmitter tum Interferer ON verify rudder stops cycling tum everything OFF 6 Measure Signal Transmitter output power record power 7 Measure Interfering Transmitter output power record power 50 results interference test plotted log-linear scales 60 Computatton Data Distance Ratio Signal-to-Receiver distance Interferer-to-Receiver distence x Interferer power Signal power Note distances can pacesor untts since interested ratio between Frequency Offset al Frequency minus Interferer Frequency Decibels x Log D 10 Log P1/P5 P1 rferer Power Watts P5 Signal Power Watts Real-World testing illustrative purposes tested Tower Gold 500 system de scribed briefly last month have crystal pairs channels RCI2 RC4O RC56 effectively covers whole 72 MHz band avail able us plus 7208 interference used Ace Silver Seven transmitter 7208 RC38 Tims Cannon transmitter 7240 Circus Apollo RC54 took everything large empty field near home no hanging cables metal fences buried pipes etc interfere test test setup Tims Quickee 500 fuselage containing Tower flight pack mounted cardboard box rocks stability Tim contact via CB continued page 42 ,uUu 1000 324 a/ 7 100 0 10 1 / / 4 0I 0 / / 506070 Use graph correlate power distance dB George tells use column Scales log-linear May 1983 41 1000 N I w ci Ll LL 100 0 0 z w 0 w U010203040 DECIBELS dB r at NORTHERN CALIFORNIAS LARGEST IDISCOUNT HOBBY SHOPI Iwell FUEL youI New high film strength lubricant ncreased power engine lifeI Highest quolily ingredients Deteraent action cut varnish JI II II II II II II II II USE YOURI MmOmd IHOUP5 MondayWednesday 9303OThursdoy&Fdday93800I L held transmitters performed test RC transmitter antennas held horizontally parallel Tims friend Marilyn Dikeman monitored airplane signalled hap penings us performed teats depicted Figure 2 obtain passband estimate plotted Figure 3 must emphasize response curve will find manufacturers litera ture curves will taken sterile labora tory conditions ceiver curve taken real world components usual places antennas close ground makes great big difference signal sources real antennas also important Holding antenna horizontally puts sys tem Horizontal Polarization radio waves go receiver antenna two ways both per pendicular antenna therefore equal strength wave goes direct through air other bounces off ground inverts wave Thus two waves arrive receiver antenna 1800 out phase affording almost total cancellation cancellation isnt total because tiny difference path length tiny reduction signal strength reflected wave since reflection isnt perfect practical result ground range antenna extended about air range overhead several miles greater air range result fact RF energy leaves antenna directions has least strength parallel antenna Any reflected wave plane sky likely have started antenna reduced power due angles volved sky range can much greater test situation have set up After plotting test data Log-Linear paper Figure 3 fitting straight line can estimate response receiver may 17dB 10 KHz off RC channel frequency find Common Carrier transmitters everyone worried about Use Figure 4 convert back forth between dB Distance Power Ratios done find corresponding Distance Ratio wer Ratio ine make use information Read Distance Ratio tells us reduced sensitivity 10 KHz away RC channel center means Common Carrier transmitter effects receiver transmitter seven times farhter away really So go back example using first part column moved interfering transmitter its beam antenna sitting 300-ft tower within mile flying field could multiply distance calculated 259 ft factor seven would find could flythe model about 7 x 259 ft away own transmitter before onset intereference Thats much reasonable diehards would like solve Maximum Safe Altitude formula again just see really gives same result would go way G1 12 x 300 x 1 _ P2G225x51176 h mi x 5280 1811 ft Close enough However result shows Tower Gold 500 owners could fly airplanes field Alternatively Power Ratio tells us reduced sensitivity lO KHz away RC Continued page 147 42 Model Aviation BUILDS WING STAB & FUSELAGE CHOICE OF MODELERS THE WORLDOVER Standard $5995 Fuse-Jig sooo Full House Wing JigKitWing & Fuse Jig Ajustojig CO R R 1 Box 673 NobIosyill, Indiana 46060 317 877 2223 Whether consider yourself novice expert model builder A-Justo Jig will improve aircraft construc tion e valuable time bargain A-Justo-Jig holds major com ponents proper alignment entire unit will rotate 36O permit fit glue plank shape sand con venient position No messy glu ing over plans waiting dry before beginning opposite side A-Justo-Jig will adjust rib former spacing lets build-in wing dihedral strong warp-free construction TO USE simple template rib indexing tool included locate drill holes rib alignment rods easy preparation takes approx 15 minutes average wing A-Justo-Jig builds em better Ask favorite hobby dealer Youll glad did rantee sockets Its simple effective common remarks will hear flying field someone asks Did make kit plans will reply followed plans part changed wherever different idea thought better deference individual designing skills schematic details shown variations such bolting upper wing instead using rubberbands Finishing As noted earlier prototype built five different peole Bill Venable covered model Bill has RC less year meticulous workman painted cowl cabane structure covered rest MonoKote Some may prefer paint whole struc ture Its builders choice Flying prototype following sur face movements Ailerons 5/ up -in differential Elevators /2 up down Rudder right left movements Regent quite gentle responsive begin ners participated building actually flew very first flightalthough did land take off comes later hot biplane enthusiast may think Regent too much airplane 40-sized engine can say prototype fully capable of usual maneuversrolls loops Cuban eights out side loops inverted flight whatever turns No wont vertical torque rollneither could Waco Taperwing Pitcairn Mailwing Regent weighs about 7/2 lb has almost 8 sq ft wing area prototype actually weighed over 8 lb full tank fuel takes off easily climbs out rapidly Best due thick wings Regent does pick up excessive speed dive Some yes lot thats good beginners glide slow steady yet wind penetration very good Since biplanes tail-draggers bit difficult steer straight down runway takeoff case Regent due relatively light wing load ing problem minimized Takeoffs almost easy would trike gear Youll like Regent Its easy build easy fly does maneuvers its airspeed makes highly realistic moves through air looks flies like queen skies Radio Technique/Myers Continued page 42 channel center means Common Carrier transmjtter effects receiver transmjtter output power divided Power Ratio Its same thing really difference comes 12 x 300 x 1 h225 50 12 h mi x5280 ff read curve Try calculator see important thjng remem ber can make correction other Nof Both closer fly ground accurate assessment wjll Important Point should realjzc above testing would unnecessary manufacturers would supply 3 pieces information transmitter output power 2 receivers re sponse 10 KHz off channel center 3 receivers response 40 KHz off channel center may will give information terms dB down ither case read dB off Figure 4 Read straight up either Distance Power read over ratio number plea manufac turers publication information wont provide figures unless demand wont get until convince will able use fair intelligent manner think can Go get em George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 writing advertisers mention read about Model Aviation May1983 147 F 63318 Span 1 Scale 60 Engine 8-9 lbsReady Fly model has molded rigid eurathane foam white epoxy jell coat surface picks up great amount detail Fuselage wings aileron fin rudder stabilizer elevator & cowl molded ready assembly installation equipment painting hardware including scale wheels struts extras Suggested List $285 Factory Direct $228 Send SASE brochure PO Box 300 Tawas City MI U763 Great Lakes Model Mold o 172-N7s
Edition: Model Aviation - 1983/05
Page Numbers: 40, 41, 42, 147
a loec ni ue George M Myers INTERFERENCE Now have new RC channels everyone worried about interference commercial transmitters might ex ample ask District Frequency Coordinator about such transmitters near flying site might point out data supplied AMA HQ Common Carrier transmitter rated 25 Watts looking through 1400 beam antnna mounted 300-ft-high tower time panic antenna 10 miles flying site First have know power output transmitter Either manufacturer will tell wont wont break line transmitter battery pack ON/OFF switch install milliammeter should have full-scale value 250 mA Read current transmitter operating normally antenna extended unplug crystal RF module read again difference multiplied battery voltage power input RF section 50% reasonable esti mate RF section efficiency take half input power being power output can expect find value somewhere between 1/4 Watt 250 mW 750 mW 72 MHz transmitter Since know received power drops off square distance between transmitter receiver can calculate maximum safe altitude fly formula h2 — PG N2P2G2 Whereh N P1 P2 maximum safe altitude miles number miles interferer Your transmitters output Watts Your antenna gain number Interferer transmitter output Watts His antenna gain number lving h2 substituting h2N2P1G1102x300x1 _ 30 P2G225x5 h 49 example 1 have substituted 300 Watts transmitter since representative older transmitters some new ones have assigned gain 5 interferers beam antenna advice friend Duffy Galle gro electronics engineer antenna specialist Duffy helped learn enough write column Taking square root cal culator find h 049 miles 049 mi X 5280 ft per mi ft should adequate purposes calculation assumes two things receiver responds equally well control signal interference typical wideband receiver exposed Com mon Carrier transmitter 10 KHz away 2 interfering transmitter located high enough can see over curve AMA SAFETY CODE TEST 100400 1000 AIRPLANE OR TOWER HEIGHT FEET 40 Model Aviation 1000 Co w -J z 0 N 0 0 10 1 310 10000 can use graph find distance radio horizon high-frequency transmission Please note scales both logarithmic month George gives relatively painless quick way check potential radio interferences coming new age RC new channels available now near future will become vital George ran series tests new Tower 500 radio see resistant adjacentchannel interference results interesting can same other systems gather information club Note antennas held horizontally parallel other Control signal transmitter tuned aircraft system Walk Out until reach limit reliable ground range keep cycling channel George used rudder walk towards model interference transmitter until starts causing control glitches model Since interested relative distances between plane two transmitters can just pace oft distance record earth airplane practical fact VHF radio waves travel straight lines radio horizon transmitter conforms Figure same true receiver radius intluence extends distance equal sum interfering transmitters radio hor izon receivers radio horizon num ber case 15 plus 40 55 miles influence certainly can felt 10 miles Due its antenna height other transmitter can see planes parked flight line something consider cause transmitters power low enough can fly up 2500 feet xour transmitter before interferencc sets Lets move other transmitter little closer say mile field see what happens h 049mi 125 049 x 5280 ft think defines field suitable Helicopters marginally theyre using wideband receivers As can see its simple calculation can quickly made cheap pocket calculator anyone should need Some interferences can happen right field Jack Albrecht National Sales Manager Kraft Systems Frequency Committee member preparing Phase-In plan has pointed out certain new channels IS KHz High Side local oscillator frequency old channels combinations 72081RC38 72 l6/RC42 7224/RC46 72 32/RC5O 7240/RC54 converted wideband receiver new channel non-converted wideband receiver old system interference might occur flying same flight line does occur have pairs share same frequency pin clipboard send one-half pair fly nearby field isnt such bad idea can work channel-splitting another club Once split guys will better off some folks other channels An Adjacent-Channel Interference Test started idea 72 MHz 010 MEASURED RESPONSE dB 203040 RC4O/RC3 / 7208/RC54 7208/RC38 RC4O/7240 LD RC CH NNEL 2/7208 RC5i NE /RC54 RC CHAN tEL WORST CASE ESTIMATED RESPONSE COMMON CARRIER 10KHZ OFFSET transmitters radiate approximately same power worked simple No Tools technique might use assess adjacent-channel sensitivity RC receiver Lets begin test plan show data developed use assess interference potential Common Carrier transmitters 10 KHz away new RC channels Test Plan Test Objective Determine Distance Ratio interference equal-power adjacent-channel transmitters Test Setup Receiver sy m non metallic support 2 Signal Transmitter maxtmum range control non-metallic support 3 Interfering Transmitter maximum range interfere control non-metallic support 4 antennas horizontal parallel mounted three feet above ground Test Procedure Verify Signal Transmitter Receiver same frequency ON 2 Verify interferer adjacent channel OFF 3 Walk Signal Transmitter out maximum range control count record paces Receiver keep cycling rudder control 4 Turn Interfering Transmitter ON walk Interferer out maximum distance between Interfering Transmitter Receiver will interfere control record distance Receiver 5 Tum Interferer OFF verify control Signal Transmitter tum Interferer ON verify rudder stops cycling tum everything OFF 6 Measure Signal Transmitter output power record power 7 Measure Interfering Transmitter output power record power 50 results interference test plotted log-linear scales 60 Computatton Data Distance Ratio Signal-to-Receiver distance Interferer-to-Receiver distence x Interferer power Signal power Note distances can pacesor untts since interested ratio between Frequency Offset al Frequency minus Interferer Frequency Decibels x Log D 10 Log P1/P5 P1 rferer Power Watts P5 Signal Power Watts Real-World testing illustrative purposes tested Tower Gold 500 system de scribed briefly last month have crystal pairs channels RCI2 RC4O RC56 effectively covers whole 72 MHz band avail able us plus 7208 interference used Ace Silver Seven transmitter 7208 RC38 Tims Cannon transmitter 7240 Circus Apollo RC54 took everything large empty field near home no hanging cables metal fences buried pipes etc interfere test test setup Tims Quickee 500 fuselage containing Tower flight pack mounted cardboard box rocks stability Tim contact via CB continued page 42 ,uUu 1000 324 a/ 7 100 0 10 1 / / 4 0I 0 / / 506070 Use graph correlate power distance dB George tells use column Scales log-linear May 1983 41 1000 N I w ci Ll LL 100 0 0 z w 0 w U010203040 DECIBELS dB r at NORTHERN CALIFORNIAS LARGEST IDISCOUNT HOBBY SHOPI Iwell FUEL youI New high film strength lubricant ncreased power engine lifeI Highest quolily ingredients Deteraent action cut varnish JI II II II II II II II II USE YOURI MmOmd IHOUP5 MondayWednesday 9303OThursdoy&Fdday93800I L held transmitters performed test RC transmitter antennas held horizontally parallel Tims friend Marilyn Dikeman monitored airplane signalled hap penings us performed teats depicted Figure 2 obtain passband estimate plotted Figure 3 must emphasize response curve will find manufacturers litera ture curves will taken sterile labora tory conditions ceiver curve taken real world components usual places antennas close ground makes great big difference signal sources real antennas also important Holding antenna horizontally puts sys tem Horizontal Polarization radio waves go receiver antenna two ways both per pendicular antenna therefore equal strength wave goes direct through air other bounces off ground inverts wave Thus two waves arrive receiver antenna 1800 out phase affording almost total cancellation cancellation isnt total because tiny difference path length tiny reduction signal strength reflected wave since reflection isnt perfect practical result ground range antenna extended about air range overhead several miles greater air range result fact RF energy leaves antenna directions has least strength parallel antenna Any reflected wave plane sky likely have started antenna reduced power due angles volved sky range can much greater test situation have set up After plotting test data Log-Linear paper Figure 3 fitting straight line can estimate response receiver may 17dB 10 KHz off RC channel frequency find Common Carrier transmitters everyone worried about Use Figure 4 convert back forth between dB Distance Power Ratios done find corresponding Distance Ratio wer Ratio ine make use information Read Distance Ratio tells us reduced sensitivity 10 KHz away RC channel center means Common Carrier transmitter effects receiver transmitter seven times farhter away really So go back example using first part column moved interfering transmitter its beam antenna sitting 300-ft tower within mile flying field could multiply distance calculated 259 ft factor seven would find could flythe model about 7 x 259 ft away own transmitter before onset intereference Thats much reasonable diehards would like solve Maximum Safe Altitude formula again just see really gives same result would go way G1 12 x 300 x 1 _ P2G225x51176 h mi x 5280 1811 ft Close enough However result shows Tower Gold 500 owners could fly airplanes field Alternatively Power Ratio tells us reduced sensitivity lO KHz away RC Continued page 147 42 Model Aviation BUILDS WING STAB & FUSELAGE CHOICE OF MODELERS THE WORLDOVER Standard $5995 Fuse-Jig sooo Full House Wing JigKitWing & Fuse Jig Ajustojig CO R R 1 Box 673 NobIosyill, Indiana 46060 317 877 2223 Whether consider yourself novice expert model builder A-Justo Jig will improve aircraft construc tion e valuable time bargain A-Justo-Jig holds major com ponents proper alignment entire unit will rotate 36O permit fit glue plank shape sand con venient position No messy glu ing over plans waiting dry before beginning opposite side A-Justo-Jig will adjust rib former spacing lets build-in wing dihedral strong warp-free construction TO USE simple template rib indexing tool included locate drill holes rib alignment rods easy preparation takes approx 15 minutes average wing A-Justo-Jig builds em better Ask favorite hobby dealer Youll glad did rantee sockets Its simple effective common remarks will hear flying field someone asks Did make kit plans will reply followed plans part changed wherever different idea thought better deference individual designing skills schematic details shown variations such bolting upper wing instead using rubberbands Finishing As noted earlier prototype built five different peole Bill Venable covered model Bill has RC less year meticulous workman painted cowl cabane structure covered rest MonoKote Some may prefer paint whole struc ture Its builders choice Flying prototype following sur face movements Ailerons 5/ up -in differential Elevators /2 up down Rudder right left movements Regent quite gentle responsive begin ners participated building actually flew very first flightalthough did land take off comes later hot biplane enthusiast may think Regent too much airplane 40-sized engine can say prototype fully capable of usual maneuversrolls loops Cuban eights out side loops inverted flight whatever turns No wont vertical torque rollneither could Waco Taperwing Pitcairn Mailwing Regent weighs about 7/2 lb has almost 8 sq ft wing area prototype actually weighed over 8 lb full tank fuel takes off easily climbs out rapidly Best due thick wings Regent does pick up excessive speed dive Some yes lot thats good beginners glide slow steady yet wind penetration very good Since biplanes tail-draggers bit difficult steer straight down runway takeoff case Regent due relatively light wing load ing problem minimized Takeoffs almost easy would trike gear Youll like Regent Its easy build easy fly does maneuvers its airspeed makes highly realistic moves through air looks flies like queen skies Radio Technique/Myers Continued page 42 channel center means Common Carrier transmjtter effects receiver transmjtter output power divided Power Ratio Its same thing really difference comes 12 x 300 x 1 h225 50 12 h mi x5280 ff read curve Try calculator see important thjng remem ber can make correction other Nof Both closer fly ground accurate assessment wjll Important Point should realjzc above testing would unnecessary manufacturers would supply 3 pieces information transmitter output power 2 receivers re sponse 10 KHz off channel center 3 receivers response 40 KHz off channel center may will give information terms dB down ither case read dB off Figure 4 Read straight up either Distance Power read over ratio number plea manufac turers publication information wont provide figures unless demand wont get until convince will able use fair intelligent manner think can Go get em George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 writing advertisers mention read about Model Aviation May1983 147 F 63318 Span 1 Scale 60 Engine 8-9 lbsReady Fly model has molded rigid eurathane foam white epoxy jell coat surface picks up great amount detail Fuselage wings aileron fin rudder stabilizer elevator & cowl molded ready assembly installation equipment painting hardware including scale wheels struts extras Suggested List $285 Factory Direct $228 Send SASE brochure PO Box 300 Tawas City MI U763 Great Lakes Model Mold o 172-N7s
Edition: Model Aviation - 1983/05
Page Numbers: 40, 41, 42, 147
a loec ni ue George M Myers INTERFERENCE Now have new RC channels everyone worried about interference commercial transmitters might ex ample ask District Frequency Coordinator about such transmitters near flying site might point out data supplied AMA HQ Common Carrier transmitter rated 25 Watts looking through 1400 beam antnna mounted 300-ft-high tower time panic antenna 10 miles flying site First have know power output transmitter Either manufacturer will tell wont wont break line transmitter battery pack ON/OFF switch install milliammeter should have full-scale value 250 mA Read current transmitter operating normally antenna extended unplug crystal RF module read again difference multiplied battery voltage power input RF section 50% reasonable esti mate RF section efficiency take half input power being power output can expect find value somewhere between 1/4 Watt 250 mW 750 mW 72 MHz transmitter Since know received power drops off square distance between transmitter receiver can calculate maximum safe altitude fly formula h2 — PG N2P2G2 Whereh N P1 P2 maximum safe altitude miles number miles interferer Your transmitters output Watts Your antenna gain number Interferer transmitter output Watts His antenna gain number lving h2 substituting h2N2P1G1102x300x1 _ 30 P2G225x5 h 49 example 1 have substituted 300 Watts transmitter since representative older transmitters some new ones have assigned gain 5 interferers beam antenna advice friend Duffy Galle gro electronics engineer antenna specialist Duffy helped learn enough write column Taking square root cal culator find h 049 miles 049 mi X 5280 ft per mi ft should adequate purposes calculation assumes two things receiver responds equally well control signal interference typical wideband receiver exposed Com mon Carrier transmitter 10 KHz away 2 interfering transmitter located high enough can see over curve AMA SAFETY CODE TEST 100400 1000 AIRPLANE OR TOWER HEIGHT FEET 40 Model Aviation 1000 Co w -J z 0 N 0 0 10 1 310 10000 can use graph find distance radio horizon high-frequency transmission Please note scales both logarithmic month George gives relatively painless quick way check potential radio interferences coming new age RC new channels available now near future will become vital George ran series tests new Tower 500 radio see resistant adjacentchannel interference results interesting can same other systems gather information club Note antennas held horizontally parallel other Control signal transmitter tuned aircraft system Walk Out until reach limit reliable ground range keep cycling channel George used rudder walk towards model interference transmitter until starts causing control glitches model Since interested relative distances between plane two transmitters can just pace oft distance record earth airplane practical fact VHF radio waves travel straight lines radio horizon transmitter conforms Figure same true receiver radius intluence extends distance equal sum interfering transmitters radio hor izon receivers radio horizon num ber case 15 plus 40 55 miles influence certainly can felt 10 miles Due its antenna height other transmitter can see planes parked flight line something consider cause transmitters power low enough can fly up 2500 feet xour transmitter before interferencc sets Lets move other transmitter little closer say mile field see what happens h 049mi 125 049 x 5280 ft think defines field suitable Helicopters marginally theyre using wideband receivers As can see its simple calculation can quickly made cheap pocket calculator anyone should need Some interferences can happen right field Jack Albrecht National Sales Manager Kraft Systems Frequency Committee member preparing Phase-In plan has pointed out certain new channels IS KHz High Side local oscillator frequency old channels combinations 72081RC38 72 l6/RC42 7224/RC46 72 32/RC5O 7240/RC54 converted wideband receiver new channel non-converted wideband receiver old system interference might occur flying same flight line does occur have pairs share same frequency pin clipboard send one-half pair fly nearby field isnt such bad idea can work channel-splitting another club Once split guys will better off some folks other channels An Adjacent-Channel Interference Test started idea 72 MHz 010 MEASURED RESPONSE dB 203040 RC4O/RC3 / 7208/RC54 7208/RC38 RC4O/7240 LD RC CH NNEL 2/7208 RC5i NE /RC54 RC CHAN tEL WORST CASE ESTIMATED RESPONSE COMMON CARRIER 10KHZ OFFSET transmitters radiate approximately same power worked simple No Tools technique might use assess adjacent-channel sensitivity RC receiver Lets begin test plan show data developed use assess interference potential Common Carrier transmitters 10 KHz away new RC channels Test Plan Test Objective Determine Distance Ratio interference equal-power adjacent-channel transmitters Test Setup Receiver sy m non metallic support 2 Signal Transmitter maxtmum range control non-metallic support 3 Interfering Transmitter maximum range interfere control non-metallic support 4 antennas horizontal parallel mounted three feet above ground Test Procedure Verify Signal Transmitter Receiver same frequency ON 2 Verify interferer adjacent channel OFF 3 Walk Signal Transmitter out maximum range control count record paces Receiver keep cycling rudder control 4 Turn Interfering Transmitter ON walk Interferer out maximum distance between Interfering Transmitter Receiver will interfere control record distance Receiver 5 Tum Interferer OFF verify control Signal Transmitter tum Interferer ON verify rudder stops cycling tum everything OFF 6 Measure Signal Transmitter output power record power 7 Measure Interfering Transmitter output power record power 50 results interference test plotted log-linear scales 60 Computatton Data Distance Ratio Signal-to-Receiver distance Interferer-to-Receiver distence x Interferer power Signal power Note distances can pacesor untts since interested ratio between Frequency Offset al Frequency minus Interferer Frequency Decibels x Log D 10 Log P1/P5 P1 rferer Power Watts P5 Signal Power Watts Real-World testing illustrative purposes tested Tower Gold 500 system de scribed briefly last month have crystal pairs channels RCI2 RC4O RC56 effectively covers whole 72 MHz band avail able us plus 7208 interference used Ace Silver Seven transmitter 7208 RC38 Tims Cannon transmitter 7240 Circus Apollo RC54 took everything large empty field near home no hanging cables metal fences buried pipes etc interfere test test setup Tims Quickee 500 fuselage containing Tower flight pack mounted cardboard box rocks stability Tim contact via CB continued page 42 ,uUu 1000 324 a/ 7 100 0 10 1 / / 4 0I 0 / / 506070 Use graph correlate power distance dB George tells use column Scales log-linear May 1983 41 1000 N I w ci Ll LL 100 0 0 z w 0 w U010203040 DECIBELS dB r at NORTHERN CALIFORNIAS LARGEST IDISCOUNT HOBBY SHOPI Iwell FUEL youI New high film strength lubricant ncreased power engine lifeI Highest quolily ingredients Deteraent action cut varnish JI II II II II II II II II USE YOURI MmOmd IHOUP5 MondayWednesday 9303OThursdoy&Fdday93800I L held transmitters performed test RC transmitter antennas held horizontally parallel Tims friend Marilyn Dikeman monitored airplane signalled hap penings us performed teats depicted Figure 2 obtain passband estimate plotted Figure 3 must emphasize response curve will find manufacturers litera ture curves will taken sterile labora tory conditions ceiver curve taken real world components usual places antennas close ground makes great big difference signal sources real antennas also important Holding antenna horizontally puts sys tem Horizontal Polarization radio waves go receiver antenna two ways both per pendicular antenna therefore equal strength wave goes direct through air other bounces off ground inverts wave Thus two waves arrive receiver antenna 1800 out phase affording almost total cancellation cancellation isnt total because tiny difference path length tiny reduction signal strength reflected wave since reflection isnt perfect practical result ground range antenna extended about air range overhead several miles greater air range result fact RF energy leaves antenna directions has least strength parallel antenna Any reflected wave plane sky likely have started antenna reduced power due angles volved sky range can much greater test situation have set up After plotting test data Log-Linear paper Figure 3 fitting straight line can estimate response receiver may 17dB 10 KHz off RC channel frequency find Common Carrier transmitters everyone worried about Use Figure 4 convert back forth between dB Distance Power Ratios done find corresponding Distance Ratio wer Ratio ine make use information Read Distance Ratio tells us reduced sensitivity 10 KHz away RC channel center means Common Carrier transmitter effects receiver transmitter seven times farhter away really So go back example using first part column moved interfering transmitter its beam antenna sitting 300-ft tower within mile flying field could multiply distance calculated 259 ft factor seven would find could flythe model about 7 x 259 ft away own transmitter before onset intereference Thats much reasonable diehards would like solve Maximum Safe Altitude formula again just see really gives same result would go way G1 12 x 300 x 1 _ P2G225x51176 h mi x 5280 1811 ft Close enough However result shows Tower Gold 500 owners could fly airplanes field Alternatively Power Ratio tells us reduced sensitivity lO KHz away RC Continued page 147 42 Model Aviation BUILDS WING STAB & FUSELAGE CHOICE OF MODELERS THE WORLDOVER Standard $5995 Fuse-Jig sooo Full House Wing JigKitWing & Fuse Jig Ajustojig CO R R 1 Box 673 NobIosyill, Indiana 46060 317 877 2223 Whether consider yourself novice expert model builder A-Justo Jig will improve aircraft construc tion e valuable time bargain A-Justo-Jig holds major com ponents proper alignment entire unit will rotate 36O permit fit glue plank shape sand con venient position No messy glu ing over plans waiting dry before beginning opposite side A-Justo-Jig will adjust rib former spacing lets build-in wing dihedral strong warp-free construction TO USE simple template rib indexing tool included locate drill holes rib alignment rods easy preparation takes approx 15 minutes average wing A-Justo-Jig builds em better Ask favorite hobby dealer Youll glad did rantee sockets Its simple effective common remarks will hear flying field someone asks Did make kit plans will reply followed plans part changed wherever different idea thought better deference individual designing skills schematic details shown variations such bolting upper wing instead using rubberbands Finishing As noted earlier prototype built five different peole Bill Venable covered model Bill has RC less year meticulous workman painted cowl cabane structure covered rest MonoKote Some may prefer paint whole struc ture Its builders choice Flying prototype following sur face movements Ailerons 5/ up -in differential Elevators /2 up down Rudder right left movements Regent quite gentle responsive begin ners participated building actually flew very first flightalthough did land take off comes later hot biplane enthusiast may think Regent too much airplane 40-sized engine can say prototype fully capable of usual maneuversrolls loops Cuban eights out side loops inverted flight whatever turns No wont vertical torque rollneither could Waco Taperwing Pitcairn Mailwing Regent weighs about 7/2 lb has almost 8 sq ft wing area prototype actually weighed over 8 lb full tank fuel takes off easily climbs out rapidly Best due thick wings Regent does pick up excessive speed dive Some yes lot thats good beginners glide slow steady yet wind penetration very good Since biplanes tail-draggers bit difficult steer straight down runway takeoff case Regent due relatively light wing load ing problem minimized Takeoffs almost easy would trike gear Youll like Regent Its easy build easy fly does maneuvers its airspeed makes highly realistic moves through air looks flies like queen skies Radio Technique/Myers Continued page 42 channel center means Common Carrier transmjtter effects receiver transmjtter output power divided Power Ratio Its same thing really difference comes 12 x 300 x 1 h225 50 12 h mi x5280 ff read curve Try calculator see important thjng remem ber can make correction other Nof Both closer fly ground accurate assessment wjll Important Point should realjzc above testing would unnecessary manufacturers would supply 3 pieces information transmitter output power 2 receivers re sponse 10 KHz off channel center 3 receivers response 40 KHz off channel center may will give information terms dB down ither case read dB off Figure 4 Read straight up either Distance Power read over ratio number plea manufac turers publication information wont provide figures unless demand wont get until convince will able use fair intelligent manner think can Go get em George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 writing advertisers mention read about Model Aviation May1983 147 F 63318 Span 1 Scale 60 Engine 8-9 lbsReady Fly model has molded rigid eurathane foam white epoxy jell coat surface picks up great amount detail Fuselage wings aileron fin rudder stabilizer elevator & cowl molded ready assembly installation equipment painting hardware including scale wheels struts extras Suggested List $285 Factory Direct $228 Send SASE brochure PO Box 300 Tawas City MI U763 Great Lakes Model Mold o 172-N7s
Edition: Model Aviation - 1983/05
Page Numbers: 40, 41, 42, 147
a loec ni ue George M Myers INTERFERENCE Now have new RC channels everyone worried about interference commercial transmitters might ex ample ask District Frequency Coordinator about such transmitters near flying site might point out data supplied AMA HQ Common Carrier transmitter rated 25 Watts looking through 1400 beam antnna mounted 300-ft-high tower time panic antenna 10 miles flying site First have know power output transmitter Either manufacturer will tell wont wont break line transmitter battery pack ON/OFF switch install milliammeter should have full-scale value 250 mA Read current transmitter operating normally antenna extended unplug crystal RF module read again difference multiplied battery voltage power input RF section 50% reasonable esti mate RF section efficiency take half input power being power output can expect find value somewhere between 1/4 Watt 250 mW 750 mW 72 MHz transmitter Since know received power drops off square distance between transmitter receiver can calculate maximum safe altitude fly formula h2 — PG N2P2G2 Whereh N P1 P2 maximum safe altitude miles number miles interferer Your transmitters output Watts Your antenna gain number Interferer transmitter output Watts His antenna gain number lving h2 substituting h2N2P1G1102x300x1 _ 30 P2G225x5 h 49 example 1 have substituted 300 Watts transmitter since representative older transmitters some new ones have assigned gain 5 interferers beam antenna advice friend Duffy Galle gro electronics engineer antenna specialist Duffy helped learn enough write column Taking square root cal culator find h 049 miles 049 mi X 5280 ft per mi ft should adequate purposes calculation assumes two things receiver responds equally well control signal interference typical wideband receiver exposed Com mon Carrier transmitter 10 KHz away 2 interfering transmitter located high enough can see over curve AMA SAFETY CODE TEST 100400 1000 AIRPLANE OR TOWER HEIGHT FEET 40 Model Aviation 1000 Co w -J z 0 N 0 0 10 1 310 10000 can use graph find distance radio horizon high-frequency transmission Please note scales both logarithmic month George gives relatively painless quick way check potential radio interferences coming new age RC new channels available now near future will become vital George ran series tests new Tower 500 radio see resistant adjacentchannel interference results interesting can same other systems gather information club Note antennas held horizontally parallel other Control signal transmitter tuned aircraft system Walk Out until reach limit reliable ground range keep cycling channel George used rudder walk towards model interference transmitter until starts causing control glitches model Since interested relative distances between plane two transmitters can just pace oft distance record earth airplane practical fact VHF radio waves travel straight lines radio horizon transmitter conforms Figure same true receiver radius intluence extends distance equal sum interfering transmitters radio hor izon receivers radio horizon num ber case 15 plus 40 55 miles influence certainly can felt 10 miles Due its antenna height other transmitter can see planes parked flight line something consider cause transmitters power low enough can fly up 2500 feet xour transmitter before interferencc sets Lets move other transmitter little closer say mile field see what happens h 049mi 125 049 x 5280 ft think defines field suitable Helicopters marginally theyre using wideband receivers As can see its simple calculation can quickly made cheap pocket calculator anyone should need Some interferences can happen right field Jack Albrecht National Sales Manager Kraft Systems Frequency Committee member preparing Phase-In plan has pointed out certain new channels IS KHz High Side local oscillator frequency old channels combinations 72081RC38 72 l6/RC42 7224/RC46 72 32/RC5O 7240/RC54 converted wideband receiver new channel non-converted wideband receiver old system interference might occur flying same flight line does occur have pairs share same frequency pin clipboard send one-half pair fly nearby field isnt such bad idea can work channel-splitting another club Once split guys will better off some folks other channels An Adjacent-Channel Interference Test started idea 72 MHz 010 MEASURED RESPONSE dB 203040 RC4O/RC3 / 7208/RC54 7208/RC38 RC4O/7240 LD RC CH NNEL 2/7208 RC5i NE /RC54 RC CHAN tEL WORST CASE ESTIMATED RESPONSE COMMON CARRIER 10KHZ OFFSET transmitters radiate approximately same power worked simple No Tools technique might use assess adjacent-channel sensitivity RC receiver Lets begin test plan show data developed use assess interference potential Common Carrier transmitters 10 KHz away new RC channels Test Plan Test Objective Determine Distance Ratio interference equal-power adjacent-channel transmitters Test Setup Receiver sy m non metallic support 2 Signal Transmitter maxtmum range control non-metallic support 3 Interfering Transmitter maximum range interfere control non-metallic support 4 antennas horizontal parallel mounted three feet above ground Test Procedure Verify Signal Transmitter Receiver same frequency ON 2 Verify interferer adjacent channel OFF 3 Walk Signal Transmitter out maximum range control count record paces Receiver keep cycling rudder control 4 Turn Interfering Transmitter ON walk Interferer out maximum distance between Interfering Transmitter Receiver will interfere control record distance Receiver 5 Tum Interferer OFF verify control Signal Transmitter tum Interferer ON verify rudder stops cycling tum everything OFF 6 Measure Signal Transmitter output power record power 7 Measure Interfering Transmitter output power record power 50 results interference test plotted log-linear scales 60 Computatton Data Distance Ratio Signal-to-Receiver distance Interferer-to-Receiver distence x Interferer power Signal power Note distances can pacesor untts since interested ratio between Frequency Offset al Frequency minus Interferer Frequency Decibels x Log D 10 Log P1/P5 P1 rferer Power Watts P5 Signal Power Watts Real-World testing illustrative purposes tested Tower Gold 500 system de scribed briefly last month have crystal pairs channels RCI2 RC4O RC56 effectively covers whole 72 MHz band avail able us plus 7208 interference used Ace Silver Seven transmitter 7208 RC38 Tims Cannon transmitter 7240 Circus Apollo RC54 took everything large empty field near home no hanging cables metal fences buried pipes etc interfere test test setup Tims Quickee 500 fuselage containing Tower flight pack mounted cardboard box rocks stability Tim contact via CB continued page 42 ,uUu 1000 324 a/ 7 100 0 10 1 / / 4 0I 0 / / 506070 Use graph correlate power distance dB George tells use column Scales log-linear May 1983 41 1000 N I w ci Ll LL 100 0 0 z w 0 w U010203040 DECIBELS dB r at NORTHERN CALIFORNIAS LARGEST IDISCOUNT HOBBY SHOPI Iwell FUEL youI New high film strength lubricant ncreased power engine lifeI Highest quolily ingredients Deteraent action cut varnish JI II II II II II II II II USE YOURI MmOmd IHOUP5 MondayWednesday 9303OThursdoy&Fdday93800I L held transmitters performed test RC transmitter antennas held horizontally parallel Tims friend Marilyn Dikeman monitored airplane signalled hap penings us performed teats depicted Figure 2 obtain passband estimate plotted Figure 3 must emphasize response curve will find manufacturers litera ture curves will taken sterile labora tory conditions ceiver curve taken real world components usual places antennas close ground makes great big difference signal sources real antennas also important Holding antenna horizontally puts sys tem Horizontal Polarization radio waves go receiver antenna two ways both per pendicular antenna therefore equal strength wave goes direct through air other bounces off ground inverts wave Thus two waves arrive receiver antenna 1800 out phase affording almost total cancellation cancellation isnt total because tiny difference path length tiny reduction signal strength reflected wave since reflection isnt perfect practical result ground range antenna extended about air range overhead several miles greater air range result fact RF energy leaves antenna directions has least strength parallel antenna Any reflected wave plane sky likely have started antenna reduced power due angles volved sky range can much greater test situation have set up After plotting test data Log-Linear paper Figure 3 fitting straight line can estimate response receiver may 17dB 10 KHz off RC channel frequency find Common Carrier transmitters everyone worried about Use Figure 4 convert back forth between dB Distance Power Ratios done find corresponding Distance Ratio wer Ratio ine make use information Read Distance Ratio tells us reduced sensitivity 10 KHz away RC channel center means Common Carrier transmitter effects receiver transmitter seven times farhter away really So go back example using first part column moved interfering transmitter its beam antenna sitting 300-ft tower within mile flying field could multiply distance calculated 259 ft factor seven would find could flythe model about 7 x 259 ft away own transmitter before onset intereference Thats much reasonable diehards would like solve Maximum Safe Altitude formula again just see really gives same result would go way G1 12 x 300 x 1 _ P2G225x51176 h mi x 5280 1811 ft Close enough However result shows Tower Gold 500 owners could fly airplanes field Alternatively Power Ratio tells us reduced sensitivity lO KHz away RC Continued page 147 42 Model Aviation BUILDS WING STAB & FUSELAGE CHOICE OF MODELERS THE WORLDOVER Standard $5995 Fuse-Jig sooo Full House Wing JigKitWing & Fuse Jig Ajustojig CO R R 1 Box 673 NobIosyill, Indiana 46060 317 877 2223 Whether consider yourself novice expert model builder A-Justo Jig will improve aircraft construc tion e valuable time bargain A-Justo-Jig holds major com ponents proper alignment entire unit will rotate 36O permit fit glue plank shape sand con venient position No messy glu ing over plans waiting dry before beginning opposite side A-Justo-Jig will adjust rib former spacing lets build-in wing dihedral strong warp-free construction TO USE simple template rib indexing tool included locate drill holes rib alignment rods easy preparation takes approx 15 minutes average wing A-Justo-Jig builds em better Ask favorite hobby dealer Youll glad did rantee sockets Its simple effective common remarks will hear flying field someone asks Did make kit plans will reply followed plans part changed wherever different idea thought better deference individual designing skills schematic details shown variations such bolting upper wing instead using rubberbands Finishing As noted earlier prototype built five different peole Bill Venable covered model Bill has RC less year meticulous workman painted cowl cabane structure covered rest MonoKote Some may prefer paint whole struc ture Its builders choice Flying prototype following sur face movements Ailerons 5/ up -in differential Elevators /2 up down Rudder right left movements Regent quite gentle responsive begin ners participated building actually flew very first flightalthough did land take off comes later hot biplane enthusiast may think Regent too much airplane 40-sized engine can say prototype fully capable of usual maneuversrolls loops Cuban eights out side loops inverted flight whatever turns No wont vertical torque rollneither could Waco Taperwing Pitcairn Mailwing Regent weighs about 7/2 lb has almost 8 sq ft wing area prototype actually weighed over 8 lb full tank fuel takes off easily climbs out rapidly Best due thick wings Regent does pick up excessive speed dive Some yes lot thats good beginners glide slow steady yet wind penetration very good Since biplanes tail-draggers bit difficult steer straight down runway takeoff case Regent due relatively light wing load ing problem minimized Takeoffs almost easy would trike gear Youll like Regent Its easy build easy fly does maneuvers its airspeed makes highly realistic moves through air looks flies like queen skies Radio Technique/Myers Continued page 42 channel center means Common Carrier transmjtter effects receiver transmjtter output power divided Power Ratio Its same thing really difference comes 12 x 300 x 1 h225 50 12 h mi x5280 ff read curve Try calculator see important thjng remem ber can make correction other Nof Both closer fly ground accurate assessment wjll Important Point should realjzc above testing would unnecessary manufacturers would supply 3 pieces information transmitter output power 2 receivers re sponse 10 KHz off channel center 3 receivers response 40 KHz off channel center may will give information terms dB down ither case read dB off Figure 4 Read straight up either Distance Power read over ratio number plea manufac turers publication information wont provide figures unless demand wont get until convince will able use fair intelligent manner think can Go get em George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 writing advertisers mention read about Model Aviation May1983 147 F 63318 Span 1 Scale 60 Engine 8-9 lbsReady Fly model has molded rigid eurathane foam white epoxy jell coat surface picks up great amount detail Fuselage wings aileron fin rudder stabilizer elevator & cowl molded ready assembly installation equipment painting hardware including scale wheels struts extras Suggested List $285 Factory Direct $228 Send SASE brochure PO Box 300 Tawas City MI U763 Great Lakes Model Mold o 172-N7s