Portable Vertical Antenna for 75m & 40m - VE2AZX

1 PortableVertical Antennafor 75m & 40mJacques VE2 AZXWeb: 20121 Objectives1- Portable Antenna for 75m et 40m2-Low radiation angle for DX3-Efficient4-Easy to install. Max height: 30 match to 50 ohms2 Designing theAntennaVertical on the Beach ?(reference 1)1 length is adjusted to resonate at the desired frequency,using an SWR analyzerMFJR adials ~ /4 EARTH1 Vertical element is adjusted to resonate at the desired frequencyMFJR adials /4 Radials are resonantEARTH3 Designing the Antenna for MHz -With a regular Vertical : 62 ft. mast is required -Too long-Radial length ~ 60 ft. -Too long-Use a Telescopic mast, 27 ft. and a 3 wire umbrella on top-Radial length~27 ft. Same as Vertical radiator heightT lescopic mast62 68 66 58 70 (3) Umbrella wires27 dropdistance:43% of 27 ft. = Design-Chosen length: 27 ft. -(22 ft. telescopic + 5 ft. pipe)-Similar to the Antenna used for DXpedition (reference 1) Antennas Here are Some Verticals on the Beach.

2 R. Dean Straw N6 BVThe ARRL Antenna Compendium Vol. 6, page 216-Radials above earth for best efficiency56 From: Rudy Severns N6LF Ref. 7 Raising Radials above Earth Increases the Gain !(On 40 m band) Portable Antenna -Will use 3 radials (27 ft.) one feet above earth and 3 umbrellawires-The resonant frequency ~ MHz, is in-between 40m and 75 m bands-The Antenna is capacitive on MHz and inductive on MHz -The reactance should not be too high on both bands, to improve matching efficiency-A remote tuner will easily match this Antenna from to MHz3 radials ~27 & MHzEARTHEARTH3 conductors #14, spaced 120 deg. ft. (16 ft. 4 in.) deg. slope~27 ftMastInsulatorTunerInsulated ft ft total (guy wire + umbrella wire)62 68 66 58 70 InsulatorNotch45 Picketwire7 Portable Antenna Tests in Brossard QC 8 BRING RESONANCE ON BOTH BANDSU sing a Parallel L-C Trap (as part of Custom Tuner)Procedure:-Find the resonant frequency without matching.

3 It should be between MHz and MHzIdeally around MHz, the geometric mean insures that the reactance will not be too high on the 75m and 40m bands,and the matching losses will be the inductance (L) required at MHz to resonate is the point of zero reactance. (Here L= uH)-Find the capacitance (C) required at MHz to resonate it.(Here C= pF)-Compute the Lp-Cp parallel values that will give the required L-C values. I provide an Excel sheet on my web site: with a Custom Tuner 103 radials 1 earth27 ft. long 120 uH @ MHzX= +148 MHzZ Antenna ~50 85 pF @ MHzX= -264 uH X= + At MHzConvert to 50 ohms :Average Radiation Resistance = ohms @ MHz(~ 8 if lossless gnd)Requires: uH effective across coaxAt MHz: Radiation Resistance ~ 60 Requires:open across uH X= + MHzRef: and with a Custom Tuner 10 uHVariable (fine tuning)502 pF233 pFActual values uH toroidT184-6 (yellow)Fo = MHzNOTE: Toroids are High Q Iron Powder NOT use ferrite cores for the resonant are too lossy andthe inductance value isNOT uH toroidT184-6 (yellow)Fo = MHz3 radials 1 earth27 ft.

4 Long 120 uH @ uH @ MHzWhat s missing ?11 Coax RG 5850 ohmsBALUNE arth groundpoint for staticdischargeUse a BalunAttentionHigh voltages presenton the radialsThis is a Vertical Antenna withelevated balun isolates the feeder from the radials. The feeder is NOT part of the radiating UsedIsolates the feeder from the elevated radials. 6 toroids similar to FT114A type 77 materialMeasured impdeance2200 at MHz1300 at MHzOverall diameter: 4 turns RG-58A13A Better BalunRef: oval toroidstype 77, 31 or 43 material5 turnsMeasured impedance3000 at MHz6000 at MHz1412345 Winding method forlarger coaxNotice the flat don t TUNER Inside ViewBalunFoamPlexiglassplateConnects to mastvia 2 screwsCoils are # 14 solid wireVariable inductor15 CUSTOM TUNERR adialsGNDThe mast goes here4 in. PVC pipe16 Portable Antenna Gnd wireSlots in the pipeto make it taperCenter SupportAl pipeTunerPVCI nsulatorPipe17 TUNER Connected to the RadialsRadials1819 RadialPortable Antenna -Details Insulator20 Portable Antenna On the beach at -CanadaSIMULATIONS with NEC Win plusGain vs Radial Length Efficiency is most critical at MHzRadial and Vertical element length ~ wavelength at MHzThe ground quality makes a big differenceUmbrella Vertical (3/7h, 45 deg.)

5 - 26 feet - MHz 3 Radials 1 ft above groundGain vs Radial Length for average and good Length Lambda Gain in dBiGain AverageGndGain GoodGnd( )21 SIMULATIONSGain vs Radial Height for Average Ground /4 Vertical and Umbrella Vertical (3/7h, 45 deg.) - 26 feet - MHz 3 Radials longGain vs Radial Height for average of Radials (ft.)Gain in dBiGAIN dB UmbrellaGAIN dB /4 VerticalNote that the umbrella Antenna has lower gain, since it has lower impedance22 SIMULATIONSGain vs Ground Type Average gndGood gndSalt waterPerfect Vertical (3/7h, 45 deg.) - 26 feet - MHz 2 Radials 1 ft above groundGain (dB) vs Gnd Type for /10 radials Gain (dB)23 Average gndGood gndSalt waterPerfect Vertical (3/7h, 45 deg.) - 26 feet - MHz 2 Radials 1 ft above groundZ feed ( ) vs Gnd Type for /10 radialsZ feed ( )SIMULATIONSA ntenna Impedance vs Ground Type For average ground, the impedance is about doubled w/r to perfect ~ 50 % of the power is lost in the earth, with an average plots at MHzGood Gnd ( 13) Average Gnd ( 13) dB25 SIMULATIONSA ntenna Currents at MHzMax current is at the base26 SIMULATIONSC omparing: dipole vs Vertical at MHzAverage ground: 13 The Vertical is equal or better than a dipole at angles below 10 28 dipole at 60 : dipole vs Vertical at MHzGood ground.

6 13 The Vertical is equal or better than a dipole at angles below 23 28 dipole at 60 plots at MHzGood Gnd ( 13) Average Gnd ( 13) dB-Gain difference is less on 40m-For both bands the radiation pattern is radiation occurs at 20 25 currents at MHzMax current is at middle of mast30 SIMULATIONSSWR on 75 mSWR changes fasterSWR on 40 m31On the Air TestsHamstickVertical32 Comparison with the Hamstick Mobile Antenna -40mThe signal from the Vertical Antenna were always strongest !Signal reports:Stations located far away: 2 S-units difference (~ 10 dB)Stations close: 1 S-unit = + 1 = dB = + 1 = dBSignal Level Comparisons on RX, 40m band, Measured DataLocal signal2 KmLocal signal~ 30Km = + 1 = dB = + 1 = dB10 dBFar Signal 950 Km10 dBSignal HamstickVertical 75-40mUsing CIAO radiosoftware1 secNote: NO fadingNote: 1 dB added to take into account coax losses (100 fti.)

7 RG-8X)When feeding the 28 ft. verticalNote:The differencechanges the Efficiciency of the Vertical Antenna on 75m-Using a regular Antenna tuner yields simpler range of impedances required is easily covered by the tuner.~ 50% efficiency on average ground with elevated radials-Use Top Loading. This will increase the Antenna radiation resistance and lower simulations predict no increase in gain over average ground at ground quality makes all the t forget the Balun ! 35 Using a Remote Tuner at the Antenna -The remote tuner is connected right at the antennaBALUNR emoteTUNERRADIOR adialsAntenna50 ohm CoaxAny lengthUsing a Tuner at the Radio end of the Coax Feedline-Use a 75 ohm cable of the recommended length. (Improves tuner efficiency)-The recommended length in feet: 93 * Vf (Where Vf is the velocity factor)-The length includes the balun. It is measured from the tuner to the antenna75 ohm CoaxRG 59 or RG-11 BALUNTUNERRADIOA ntennaRadials50 ohm CoaxAny lengthSINGLE BAND VERSIONS-No traps.

8 Vertical element length = radial length.(My simulations assume that # 12 wire is used on all conductors).-For 75 m. Use ~ ft. radials and Vertical elements. Gain improves 1 dB (over average gnd).Zantenna = 28 ohms. Compare this to a regular /4vertical at 62 ft. high. -For 40 m. Use ~ ft. radials and Vertical decreases dB (over average gnd).Zantenna = 28 standard /4vertical is 32 ft. Vertical Antenna for 75m and 40m makes up a compact 28feet high in 20 minutes by two elevated radials for higher gain. 5 to 6 dB improvement as measured on 40mby Rudy Severns standard / remote tuner at the feedpoint will ease construction and allow operationfrom to MHz. The self resonant frequency should be between MHz and MHz to improve matching did not show gain improvements using top distribution in the radials -Currents should be equal for omni / soil condition may affect current Severns recommends 10 12 radials to minimize a balun to feed this Antenna , since itbehaves as a Vertical dipole.

9 Connect the remote tuner between the balun and the Here are Some Verticals on the Dean Straw N6 BVThe ARRL Antenna Compendium Vol. 6, page 216 The author uses 2 elevated radials, resonated separately as a dipole at the desired frequency. Operation near salt Radials for Ground-Plane Antennas Rudy Stevens N6 LFThe ARRL Antenna Compendium Vol. 6, page 212 Lots of data on using 4 elevated radials on 160 m3-An Electrically Small Umbrella Antenna for 160 MetersJohn S. Belrose VE2CV The ARRL Antenna Compendium Vol. 7 Uses a short elevated tuned radial4-Elevated radial systems for vertically polarized ground-plane type antennasJohn S. Belrose VE2CV Communications Quarterly winter 1998 Basic data at MHz where thenumber of radials is varied from 4 to 64 and radial height varies from lambda (5mm) to Vertical Antennas and Ground Systems Ralph Holland VK1 elevated Umbrella Top Loaded Vertical Antenna John S.

10 Belrose VE2 CVHam Radio September 1982. Basic construction data. Radialsat the ground Closer Look at Vertical Antennas With Elevated Ground SystemsRudy Severns N6 LFAntenneX March 2012 or QEX March / April Antenna for 40 and 75meters Paul A Scholz W6 PYK Ham Radio September 1979 Available from the author of this Built Verticals Using Umbrellas41 Commercially Built Verticals Using Umbrellas42 Marconi Museum -Glace Bay / Cap Breton Island Nova Scotia -Canada43 Marconi Vertical Antenna System44 Building one of the four Towers45 What Remains Today of Marconi s Antenna46 Looking East, Facing the AtlanticWhere Marconi had his Antenna47 Looking South48 ENDJ acques VE2 AZXWeb.