G5RV according to G5RV

Introduction

A G5RV is an antenna system described by Louis Varney, G5RV, in several articles from 1958 to 1984.

A G5RV has been in use at VK1OD for six months.

The configuration in use is the so called tuned feeders  configuration, ie the dipole is fed entirely with open wire feed line from the ATU/ balun to the dipole centre. The implementation is described in detail, and performance verification detailed at Bowral G5RV for local contacts.

Use of the G5RV attracts frequent reaction from self appointed experts on what is and what is not a G5RV. There is an insistence by many that a G5RV has a hybrid open wire / coax feed system; that anything else is not a G5RV.

Tuned feeders

In his 1958 article, Varney wrote:

Two versions of it were tested; one using open wire tuned feeders and the other using a 34ft open wire stub fed at its base by either 72Ω coax or 72Ω twin-lead;

 and:

Alternatively, open wire feeder may be employed from the centre of the aerial right back to the transmitter output or ATU.

That article also included the following schematic.

Fig 1:

Fig 1 is Varney's schematic where he shows the tuned feeder arrangement. L1, L2 and C1 were typical of ATUs of the day, and 72Ω coax would have been recommended as it was more commonly available than 50Ω as war surplus at the time. (72Ω twin-lead is not a practical product and was dropped from the market.)

He recommended the tuned feeder configuration over the hybrid feed for some bands:

On 21MHz ... is capable of good results, especially when using tuned feeders...

and:

On 28MHz ... Here again, results are better with a tuned feeder to minimise losses...

Clearly, not only was solely open wire feeder (tuned feeders) an option in his mind, it is one of the configurations he tested and detailed in a schematic in his first significant article on the system.

Modern analytical and modeling tools give us insight into the operation and performance of the antenna beyond that set out in Varney's articles. One could take the view based on modern analysis that the weakest part of the common G5RV implementation is the hybrid feed configuration that has:

 It is the poor performance of the hybrid feed on some bands that gave rise to Brian Austen's ZS6BKW variant which is better than the G5RV on some bands, poorer on others, but not as good overall as a G5RV with tuned feeders.

Conclusions

We have bred hams who have formed strong opinions on things without sound research. They stand ready to sprout ham folk lore as fact, and to pass technical judgment on systems that they don't understand, and lack an open mind to learn.

The latter is not surprising, as Jonathon Swift noted [i]t is useless to attempt to reason a man out of a thing he was never reasoned into.

References / Links

Changes

Version Date Description
1.01 14/09/2013 Initial.
1.02    
1.03    
1.04    
1.05