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G5RV junior antenna (inverted V) implementation

This web page will look into measurements of an G5RV junior antenna. The following sections are covered:

• Introduction
• References
• Acknowledgements

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Introduction

This webpage provides an overview of the experience gained by building, measuring and simulating a G5RV junior antenna.

Terminology

Basics of G5RV antenna

Original article of Louis Varney [1958]: https://www.qrpforum.de/index.php?attachment/20212-g5rv-org-pdf/

Updated article by Louis Varney [1984] on full (and a tille about the junior) G5RV: https://midsussexars.org.uk/downloads/g5rv_multiband_antenna.pdf

Some information about Louis Varney and his full G5RV: https://www.youtube.com/watch?v=I28XUmbUXsA

Measuring the G5RV junior

Simulating the G5RV junior

Multiband

So looking at a G5RV junior antenna (which compares in some way with the general description of the full G5RV [1983]). The Dip frequencies, standing wave [on half-dipole and ladder) and polar diagrams are (illustratively) from MMANA-GAL simulations.
<if looking at full G5RV in MMANA-GAL, we see the similar standing wave and polar diagrams, but than for a twice lower frequency.
The standing wave diagrams for 3.5 and 7Mhz look slightly different in Varney's article [1984];

The reason could be that Varney [1984] used the Band range frequency_min, while below the Dip frequency was used).

Dip frequency of G5RV junior	Description of functioning of antenna	Z at ladder feedpoint	Standing wave diagram	Polar diagram
~7.5MHz	The half-dipole plus the ladder functions as a folded up 0.5*(λ/2) antenna	Reactive load (around 25Ω)		Elev. angle: 45deg
~16.3MHz	The half-dipole plus the ladder functions as a partially folded 1.5*(λ/2) antenna	Resistive load (around 50Ω)		Elev. angle: 34deg
~30.1MHz	The half-dipole forms a 1.5*(λ/2) long center-fed antenna, a match is obtained through the 1*(λ/2) ladder.	Resistive load (around 100Ω)		Elev. angle: 32deg
~52.3Mhz	The half-dipole forms a 2.5*(λ/2) long center-fed antenna, a match is obtained through the 2*(λ/2) ladder.	Resistive load (around 150Ω)		Elev. angle: 12deg

Some implementation considerations

Folding back

Folding back the shortened half-dipoles: https://amateurradiotechsupport.freshdesk.com/support/solutions/articles/51000082880-g5rv-multi-band-antenna
Shortening my G5RV on both half-dipoles from a 25cm folded back to (by clipping it away) a 12cm folded back; No significant difference.

Dielectric constant of insulated wires

http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/diel.html
Polyethylene (PE) insulation is being used for ladder and dipole: ~2.25

Velocity factor

Determine VF of wire: https://groups.io/g/nanovna-users/topic/velocity_factor_measurement/106153112?page=3

VF for 450Ω PE ladder 0.902: https://www.ebay.com/itm/314582526493

VF insulated dipole wire (PE Koper/RVS Litze) has according https://lowpowerlab.com/guide/rf-best-practices/velocity-factor/ an additional factor of 0.95 – 0.98 (for PVC, Polyethylene, Teflon) beside the VF=0.95 for a bare wire. So the resulting VF would between 0.90 and 0.93 for insoluaed wire.

By using a dipole simulation in NEC-2 for MMANA, an VF=0.95 was gained.
Someone though explicitly tested this insulated wire and got an VF=0.94 [pers. comm. HF kits, 2025].

Frequency band ranges

Implementing a G5RV

Building instructions

G5RV junior implementation guidelines: https://www.hfkits.com/instructions-zs6bkw-g5rv-junior-mini-includes-11-balun/

The setup of my G5RV junior antenna

Inverted V (see here for the general layout): top height 9m and the half-dipoles ends go down to around 4.8m and 5.8m (angle between the half-dipoles some 120deg).

Frequency responce of my G5RV junior

Determining the ratio between length of half-dipole+ladder and the Dip wavelength

The Dip wavelengths are determined using NanoVNA and NanoVNASaver.
If we determine a ratio of length of half-dipole plus ladder divided by λ(dip)/2; this should be constant for each bands and half-dipole or ladder lengths:

Optimum half-dipole and ladder lengths

The following have been m(easured) and s(imulated):

In below figure the half-dipole length is varied between 7.25 and 7.37m and the ladder length between 5.18 and 5.3m:

The above red coloured cell (half-dipole length: 7.37m and ladder length: 5.18m) looks to be the optimum for my setup.

A slightly different G5VR setup (lower inverted V: top at 7m and the half-dipoles ends at 3m) had the optimum half-dipole length at 7.25m and ladder length at 5.3m [pers.comm. HF kits, 2025]. So not that far off from my own experience.

Evaluation

• For 'optimum' half-dipole (7.37m) and ladder (5.18m) length: On average the SWR is around 3.5 (between 2 and 5) for 40, 20, 10 and 6m amateur bands.
• A single (auto)transformer cannot reduce the SWR: For 40m: Z<25Ω, for 20m: z~50Ω and for 10: Z~100Ω and for 6m: Z~150Ω
• Would a remote impedance transformer (at ladder start) of 1:2 (and 2:1) and 1:3 be working?
  
• The SWR for the 20m band always increases with decreasing ladder and half-dipole lengths.
• The difference between simulated and measured SWR at Dip frequencies is not always the same: for the 40m band the simulated Dip frequency is larger. While for the 20, 10 and 6m bands the simulated Dip frequencies are smaller. Luckily; one can start for most bands with a larger length and then shorten it; as the differences decrease with shorten half-dipole lengths.
  
  
• If Dip frequency and its SWRdip are known, the SWRf at an other frequency f can be determined:
  
  
• For 40 and 20m the half-dipole itself is not in resonance; the ladder is part of a resonance folded dipole.
• For 10 and 6m the half-dipole itself is at resonance.
• The elevation angle is quite high for all bands 40, 20 and 10m, so not really for DX-ing as the elevation angle in these bands is larger than 15deg. The 6m elevation angle is ok-ish for DX-ing (elevation angle <15deg); except, at that band, DX is not that opportune. For Ms (meteor scatter) a larger elevation angle would be needed.

Veryfying the VNA measurements and the ATU readings

The VNA measurements of the G5RV antenna are compared with the readings of the ATU-100 EXT device. This is done by using the Smith chart.

References

Nichols, Steve: An introduction to antenna modelling. Bedford, Radio Society of Great Britain 2014.
Varney, Louis: An effective multi-band aerial of simple construction. In: RSGB Bulletin July  (1958), pp. 19-20.
Varney, Louis: The G5RV multiband antenna ... Up-to-date. In: Radio Communications July  (1984), pp. 572-575.

Acknowledgements

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