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“Radial-Less” Verticals
“Radial-Less” Verticals -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Presented by: Keith Witney VE7KW “Radial-Less” == “Ground-screen independent” Vertical Theory Pattern, Effect of ground “Radial-less” verticals Vertical dipoles, 43’ flag poles, Counterpoise, E-H R8 example Theory, Model, Measured 10/25/2012 NSARC HF Operators 1 “Radial-Less” Verticals Vertical Theory -•-• --• - •• • ••• - • - - • •• - • ••• • -• Perfect vertical Effect of ground Radials Counterpoise Inductive loading Capacitive loading Traps Stubs 10/25/2012 NSARC HF Operators 2 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Vertical over ideal ground Perfect ground and effect of real ground Real Ground effect matters out to 100λ Near field ground (1 λ) == losses Far field ground == vertical pattern 10/25/2012 NSARC HF Operators 3 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Vertical pattern changes with length of vertical monopole 1λ4 = -.28dBi at 25º 3λ8 = -.20dBi at 25º 5λ8 = 1.85dBi at 15º 10/25/2012 NSARC HF Operators 4 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• λ/4 Z= 36 Z ~ 50 real Gnd • ••• - • - - • •• - • 3λ/8 Z=196 + j310 ••• • -• λ/2 Z=~1200-j160 End fed vert. dipole Higher Z helps with counterpoise/efficiency Lifting current maximum helps with efficiency /Gain (5.83 vs 5.15 dBi) 10/25/2012 NSARC HF Operators 5 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Efficiency = Rrad/(Rrad+Rloss) Rrad=1450 h^2/λ^2 λ/4 = 36.6 ohms 3λ/8 = 62 ohms λ/2 = 69.2 ohms Rloss Conductor R Ground R (15Ώ) Coil resistance (1Ώ) Capacitance loss 10/25/2012 NSARC HF Operators 6 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Radials: Elevated and/or Buried Vertical antennas take up as much or more room than dipoles when the radials are considered. Elevated radials should be resonant (on all bands!) . Should be 1/10λ above ground (can angle up) One will balance current, 2 will balance horizontal pattern effect, more couple to real ground more effectively Buried Radials need to be dense but can be nonresonant and shorter. Target is L>3/8 λ and a density at the end of <0.03λ 10/25/2012 NSARC HF Operators 7 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• More radials can give 3 dB for a lot of metal and space 80m and up probably easier to go multiple dipoles in the same space 10/25/2012 NSARC HF Operators 8 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Counterpoise consists of a network of wires or cables (or a metal screen) parallel to the ground, suspended from a few centimetres to several metres above the ground, under the antenna. the counterpoise functions as one plate of a large capacitor, with the conductive layers of the earth acting as the other. Capacitance increases with plate area and smaller plate spacing the counterpoise functions as a RF ground connection Placed at high impedance points A common mode choke is required 10/25/2012 NSARC HF Operators 9 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Near Field is <2λ Antenna effected by objects in the near field So for a 10m vertical, Lots >40m in the city? Far Field effects ground reflections for low-angle signals out to 100λ (8 km at 80m) Applies for all types of antennas 10/25/2012 NSARC HF Operators 10 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Short Antennas are capacitive so inductive loading compensates Inductive loading Losses related to Coil Q: Large, low R coils 10/25/2012 NSARC HF Operators 11 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• However we might want to go to a longer antenna which would be inductive Capacitive loading No R so low loss Can be disc/wires 10/25/2012 NSARC HF Operators 12 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• We need to isolate unused portions of the antenna to make it work on multiple bands Traps Isolating trap to remove unwanted parts of the antenna Shortening/lengthening traps Trap frequency is set to geometric mean of the two frequencies desired Acts an a lengthening inductor below the trap frequency Acts as a shortening capacitor above the trap frequency Traps tend to have losses associated with the coils and capacitors and can be bulky 10/25/2012 NSARC HF Operators 13 “Radial-Less” Verticals Vertical Theory -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Stubs Provide a low loss, high Q means of isolation Transmission line normally open λ/4 This creates a high impedance at the end of the stub for the frequency to which it is tuned effectively adding the stub to the point to which it is attached by creating a low impedance at this point and isolating everything else. In “radial-less” verticals typical results in a OCF radiator 10/25/2012 NSARC HF Operators 14 “Radial-Less” Verticals Examples -•-• --• - •• • ••• - • - - • •• - • ••• • -• Vertical Dipole Flag Pole Non-ground referenced (Counterpoise) E-H Antennas 10/25/2012 NSARC HF Operators 15 “Radial-Less” Verticals Examples Vertical Dipole -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Note the significant effect of ground quality (not only verticals) Elevation above “ground” can be several metres higher than soil 10/25/2012 NSARC HF Operators 16 “Radial-Less” Verticals Examples Vertical Dipole -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Force 12 Sigma 5 5 band 20 - 10m 40m 80m 160 m monoband Note the Sea Water! 10/25/2012 NSARC HF Operators 17 “Radial-Less” Verticals Examples 43 ft FlagPole -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Or 21.5’ if you don’t want 80m This is NOT a resonant antenna. A 10:1 antenna tuner is required. The tuner need not be remote if coax run is reasonably short and good quality coax is used A common mode choke is required You must do something about ground losses Multi-band radials but more likely an extensive buried ground system Stucco mesh under the grass? (Circulating currents?) 1λ4 lambda to1λ8 lambda. Can be shorter when buried. 10/25/2012 NSARC HF Operators 18 “Radial-Less” Verticals Examples 43 ft FlagPole -•-• --•- 10/25/2012 - •• • ••• - • NSARC HF Operators - - • •• - • ••• • -• 19 “Radial-Less” Verticals Example 21 ft FlagPole -•-• --•- - •• • ••• - • - - • •• - • ••• • -• 10ft by 20 ft stucco mesh 2, 10m wires along fence and around garage 10/25/2012 NSARC HF Operators 20 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Top fed to move current max up Linear decoupling stubs > 20m Counterpoise at top to increase current maximum height above ground 2m λ/4 vertical above CP! Base (Top) loaded for 30,40,80m Capacitive hat OCF to the side? 10/25/2012 NSARC HF Operators 21 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Titan DX Vertical Dipole fed at 5/8 point Cross coupled tuning rods, coaxial stubs and tuning capacitor Loop extension for 40m 10/25/2012 NSARC HF Operators 22 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• R5 10/25/2012 NSARC HF Operators 23 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• AV640 Computer optimized 3λ8 End fed, No traps; stubs 6,10,12,17m 15m center radiator terminated with C hat? Top loading coils (//) with Capacitive hats 20,30,40m 72” CP, 4:1 transformer and 1:1 current Balun 10/25/2012 NSARC HF Operators 24 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• DX77 Off-center-fed dipole Traps for each band Where is the OCF? 10/25/2012 NSARC HF Operators 25 “Radial-Less” Verticals Examples E/H Antennas -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Concept is to generate E and H fields at the same point Isotron (40 & 80m) WineGlass (2-8 MHz) 10/25/2012 NSARC HF Operators 26 “Radial-Less” Verticals Examples Counterpoise -•-• --•- - •• • ••• - • - - • •• - • ••• • -• From: HF Vertical Tests Champion Radio N0AX K7LXC 2000 Measured Values to 1/4λ GP antenna on the same ground mat. Transmit to a small loop and calibrated laboratory receiver at 171m. 10/25/2012 NSARC HF Operators 27 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• For interest: Values for a 3 el tri-bander beam E.G. TH3-MK4 “average gain 5.8 dBd or 8 dBi”. A dipole is 2.15 dBi Assuming a perfect GP reference antenna this beam would be >8.85 dB in the above tables and a dipole would be >3 dB (Max lobe) 10/25/2012 NSARC HF Operators 28 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - Measuring real performance is difficult ••• • -• 21ft over R8 20m 7 6 5 4 3 db over R8 WSPR Reverse Beacons On-Air “reports” Antenna Range Not far field - - • •• - • • 2 1 0 0 1000 2000 3000 4000 -1 -2 -3 -4 10/25/2012 NSARC HF Operators km 29 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • 8 bands; 40/30/20/17/15/12/10/6m Latest in series R4,R5,R6,R6000,R7,R7000,R8 of 1/2λ base loaded radiators ••• • -• Starting at the bottom -Mounting post: 2in minimum 10 ft above ground -Counterpoise: Capacitive base loading -Matching box: 4:1 matching transformer and CM choke -15m/12m stubs: at electrical 1/8λ point 1/4λ to create 3/8λ radiator -10m stub: at electrical 1/8λ point 1/4λ to create 3/8λ radiator -6m stubs: at electrical 3/8λ? point 1/4λ to create a 3/8λ dipole -Capacitive hat: top loading for the 17m section -17m trap -20m/30/ trap -Capacitive hat for 40m -Stinger to adjust 40m 10/25/2012 NSARC HF Operators 30 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Lot 120 ft by 33 ft Unfortunately I did not fill the front yard with wire and a flag pole when I replaced the lawn 4m drop front to back Cement tile roof! At least its not a Condo! 10/25/2012 NSARC HF Operators 31 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• VE7KW Not exactly an optimal location Anything further from the house could fall into the 8 KV hydro lines! Should probably be mounted to the Chimney boxes ultimately but then can’t be guyed This is LARGE when assembled compared to the available lot. It was built in the basement hall 30 ft long! 10/25/2012 NSARC HF Operators 32 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• CUSHCRAFT R7 – YouTube http://www.youtube.com/watch?v=4NbWQXtnQ-E http://www.youtube.com/watch?v=00BRCowetEo&f eature=related 10/25/2012 NSARC HF Operators 33 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• 30m 18.9 uH. 20m 11.8 uH, 17m 9.2 uH capacitance consists of the cylindrical capacitor between the coil and the inner tube with a plastic dielectric and the coil and the outer tube with an air dielectric 30m C1=30.82 pF C2= 50 pF C1series C2= 19 pF 20m C1=20.78 pF C2= 33.7 pF C1series C2= 12.85 pF 17m C1=15.76 pF C2= 15.7 pF C1seriesC2= 9.75 pf 10/25/2012 NSARC HF Operators 34 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• ModellingTraps Tried measuring frequency using grid dip meter and VNWA Did not match with calculations Probably because the trap L is also acting as part of the antenna balanced by top hats Acting as shortening / lengthening traps? 10/25/2012 - • - - • •• - • ••• • -• Assumption 17m 20m 30m 20120611 meas 16.94 16.94 8.42 Trouble shoot traps R7 17.5 12.92 9.9 EZNEC Re 22.4 12.8 10.5 NSARC HF Operators 35 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Modeled using EZNEC By fudging the trap frequencies I could get the resonances to match but the SWR (the model does not incorporate the 4:1 transformer!) did not match probably as trap Q not correct Modelling the stub junctions is also a problem with NEC2. 10/25/2012 NSARC HF Operators 36 “Radial-Less” Verticals R8 Example -•-• --•- 10/25/2012 - •• • ••• - • NSARC HF Operators - - • •• - • ••• • -• 37 “Radial-Less” Verticals R8 Example -•-• --•- 10/25/2012 - •• • ••• - • NSARC HF Operators - - • •• - • ••• • -• 38 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • End Fed 3λ8 radiators against CP, OCF Dipoles? ••• • -• Gain indicates OCF dipole >21 MHz Counterpoise of 7, 49” spokes lowers base impedance and couples “ground” RF current to earth capacitively Black box (R8 does not have static drain choke) has a 4:1 voltage balun to match to 50 ohms 1:1 current Balun (essential if counterpoise used) 10m, 12m and 15m λ/4 stubs at λ/8 above feed so 3λ8? 6m stub seems to be λ/4 stub at λ/4 above feed Unlikely to be end fed vertical dipole. 5λ8 ? First cross hat loads length to 20m/17m trap 3λ8 with Trap L 30m trap Second cross hat and stinger loads length to 40m 10/25/2012 NSARC HF Operators 39 “Radial-Less” Verticals R8 Example -•-• --•- - •• • ••• - • - - • •• - • ••• • -• Good Multi-band, Full Power, No Radials, Omni-directional Can use standard 3:1 internal ATU, fits a small lot Bad 3 db loss compared to a dipole (in optimal direction) Except above 21 MHz ~ = Dipole Expensive compared to “Flag-pole” (but need 10:1 ATU) Recommendation (small lot) Flag Pole if you can provide a ground Mat Hex/Spider/LP beam if you only need 20m-6m NE/SW Dipole for 80/40 if you can string it. 10/25/2012 NSARC HF Operators 40 “Radial-Less” Verticals Noisy? -•-• --•- - •• • • • • - • - - • •• - • ••• • Increase in Broadband noise compared to an inverted Vee S Units, Mid-day, IC-756 Pro III, preamp off, SSB From “Elimination of Electrical Noise” G3HVA Antenna 80m 40m Random wire 2.5-4 1-3 Windom 2.5-4 1-3 Horizontal 80m dipole 1.5-3 Horizontal G5RV 1-3 0.5-1.5 Inverted G5RV 0.5-2 0.5-1.5 Vertical 1 1 10/25/2012 NSARC HF Operators -• 41 “Radial-Less” Verticals -•-• --•- - •• • ••• - • - - • •• - • ••• • -• References Low-Band Dxing; John Devoldere ON4UN HF Vertical Tests-Methods and Results N0AX, K7LXC 10/25/2012 NSARC HF Operators 42
