Transcript Document
The Lure of The Ladder Line G5RV Antenna VE3KL Wireman551 Copper Clad Steel Core 7/17/2015 David Conn VE3KL 1 Presentation Outline • • • • • The Lure of the Ladder Line: Steve Ford QST 1993 Wes Stewart N7WS, Dan McGuire AC6LA Losses in common Transmissions lines Examples of High and Low Losses in Ladder Line The G5RV Antenna 7/17/2015 David Conn VE3KL 2 Steve Ford’s Experiment (looking for a small multi-band antenna) QST 1993 7/17/2015 David Conn VE3KL 3 First Attempt (Coaxial Feed) 66 foot dipole Used from 160 to 10 metres ! 66 Feet Thick Copper High Quality Coax RG213 Loss:0.2 dB @1.9 MHz Looks Good! 50 Feet Tuner 7/17/2015 David Conn VE3KL 4 First Attempt.. Results Total Loss = 25 dB @ 1.9 MHz Why? 66 Feet Thick Copper High Quality Coax RG213 Loss:0.2 dB @1.9 MHz 50 Feet Excellent @ 40m Half Wave Dipole 7/17/2015 Tuner David Conn VE3KL 100 W in 0.3 W Radiated 5 Second Attempt..Ladder Line Total Loss = 8.6 dB @ 1.9 MHz Why? 66 Feet Thick Copper Ladder Line Wireman 551 Loss:0.1 dB @1.9 MHz 50 Feet Tuner 7/17/2015 David Conn VE3KL 100 W in 14 W Radiated 6 Now Let’s find out Why • Wes Stewart Measured Wireman 551 Losses Used an HP VNA at 50 MHz Included the case for ice/snow • Dan McGuire included DC and Low frequencies Developed TLDetails…reflection losses Uses measurements from Wes Stewart 7/17/2015 David Conn VE3KL 7 Insertion Loss: Depends on frequency Three components to loss 1. Loss at or near DC..160 m Ladder Line 2. Skin effect Loss.. Important through HF 3. Dielectric Loss..usually small but can dominate as we will see in Ladder Line 7/17/2015 David Conn VE3KL 8 Insertion Loss: Depends on frequency Basic Formula….not complete in 1993 Loss Ko K1 * SQ RT(Fre que ncy) K 2 * Fre que ncy[dB] DC Component 7/17/2015 Skin Effect David Conn VE3KL Dielectric Loss 9 TLDetails Dan McGuire AC6LA • • • • Visual Basic Transmission Line Calculator Includes work of Wes Stewart for Ladder Line Added the effect of DC resistance Includes reflection losses assuming a perfect Antenna tuner 7/17/2015 David Conn VE3KL 10 TL Details AC6LA Given the load ZL,TLDetails solves the Telegraphers equation TX (Ideal) Tuner (Ideal) Transmission Line Load ZL Zin,SWR,all losses,RL,power,Zo,VF… ZL from measurements or simulation 7/17/2015 David Conn VE3KL 11 Common Myth Loss in Ladder line is so small it does not have to be considered in the design Let’s Challenge this 7/17/2015 David Conn VE3KL 12 TLDetails AC6LA ..the myth LMR 400 Coax Wireman 551 7/17/2015 David Conn VE3KL 13 Wireman 551 Note the scale (100 dB max.) ICE/Snow DRY 7/17/2015 David Conn VE3KL 14 Back To Steve’s Experiment Use SimSmith 7/17/2015 David Conn VE3KL 15 First Attempt 66 foot dipole Used from 160 to 10 metres! 66 Feet Thick Copper High Quality Coax RG213 Loss:0.2 dB @1.9 MHz Looks Good! 50 Feet Tuner 7/17/2015 David Conn VE3KL 16 Dominated by Reflection Losses Power in = 100 Watts RG-213 Power out = 0.315 Watts @1.8 MHz 7/17/2015 David Conn VE3KL 17 Apply Ideas to the Balanced G5RV Antenna Approximate Analysis using EZNEC,TLDetails SimSmith 7/17/2015 David Conn VE3KL 18 Balanced G5RV Antenna 31.8 metres 3λ/2 @14.15 MHz Radiator λ/2 @14.15 MHz Ladder Line Make Up Section Balun Coaxial Cable Critical 7/17/2015 Antenna Tuner David Conn VE3KL 19 Case 1 Coax Cable Length = 0 31.8 metres 3λ/2 @14.15 MHz ZAnt ZT Radiator λ/2 @14.15 MHz Ladder Line NOT a RADIATOR Balun/Tuner •Use EZNEC Antenna Simulator to find ZAnt •Use TLDetails to find ZT and Losses 7/17/2015 David Conn VE3KL 20 Case 1: Coax Cable Length = 0 Wireman 551 Ladder Line Loss (Length = 31.31 feet) Band [m] Freq [MHz] Zant [Ohms] ZT [Ohms Loss [dB] Performance 160 [1.8] 5.6 – j1521 5 – j519 7 Poor 80 [3.5] 25 – j421 17 –j14 1.7 Fair 40 [7 ] 506 + j1174 53 –j123 0.24 Excellent 30 [10.1] 1344 – j2180 77 + j409 0.6 Good 20 [14.15] 121 + j0 125 + j0 0.2 Excellent 17 [18.068] 2540 +j1700 91 –j382 0.4 Excellent 15 [21 ] 268 – j991 45 + j128 0.6 Good 12 [24.89] 233 +j412 109 + j45 0.2 Excellent 10 [28] 3030 + j169 0.4 Excellent 2194 +j1120 Length of Antenna = 103 feet Case 2 Coaxial Cable Length = 50 feet 31.8 metres 3λ/2 @14.15 MHz Radiator λ/2 @14.15 MHz Ladder Line NOT a RADIATOR Balun Coaxial Cable RG213 Critical Antenna Tuner 7/17/2015 David Conn VE3KL 22 Case 2: Coax Cable (RG213) Length = 50 feet Loss due to Coax Band [m] Freq [MHz] ZT [Ohms Coax Loss [dB] Performance 160 [1.8] 5 – j519 10.8 Poor 80 [3.5] 17 –j14 0.4 Excellent 40 [7] 53 –j123 0.8 Excellent 30 [10.1] 77 + j409 3.9 Poor 20 [14.15] 125 + j0 0.4 Excellent 17 [18.068] 91 –j382 4.0 Poor 15 [21] 45 + j128 1.5 Good 12 [24.89] 109 + j45 0.6 Excellent 10 [28] 2194 +j 1120 5.9 Poor G5RV Using SimSmith Loss @ 1.8 MHz = 18 dB Ladder Line EZNEC (Antenna) Coax Tx G5RV Summary •Works well on 80, 40, 20, 15 and 12 meters •Must set it up to resonate at 14.15 MHz •Other Losses not included: Tuner, Ant. efficiency •High SWR produces very high voltages •Needs a very high quality Tuner and Coax •Poor performance if covered with Ice/Snow Summary •Can apply the methods to most antenna systems •Wire, vertical, Yagi, Uhf •SimSMith can import measured or EZNEC data •Can include tuner losses and imperfect transmitters •Can include antenna losses •Be careful with SWR values > 3:1 73 Dave VE3KL References • • • • • Louis Varney Video: http://www.youtube.com/watch?v=46Gq5Od6m4 Balanced Transmission Lines in Current Amateur Practice, Wes Stewart, N7WS http://users.triconet.org/wesandlinda/ladder_line.pdf Steve Ford, WB8IMY, The Lure of the Ladder Line, QST Dec 1993 TLDetails, Dan Maguire, AC6LA: http://www.ac6la.com/tldetails.html SimSmith, AE6TL http://www.ae6ty.com/Smith_Charts.html 7/17/2015 David Conn VE3KL 28