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.

2 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 ..R. Dean Straw N6 BVThe ARRL Antenna Compendium Vol. 6, page 216-Radials above earth for best efficiency56 From: Rudy Severns N6LF Ref.

3 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.)

4 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. 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.

5 (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.

6 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. 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.

7 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.)

8 - 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.)

9 - 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.

10 13 The Vertical is equal or better than a dipole at angles below 10 28 dipole at 60 : dipole vs Vertical at MHzGood ground: 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 !