[Antennas] G5RV/inverted vee: Radiation Angles

Sat, 11 Jan 2003 00:11:00 +0000

In other words, the instruction sheet from Antennas West "Lied" to me when 
it said that a vee configuration would work? What I wanted was 20,30,40 
omnidirectiional...

             Durwydd MacTara

>From: "George, W5YR" <[email protected]>
>To: "Pat W" <[email protected]>, <[email protected]>
>Subject: Re: [Antennas] G5RV/inverted vee: Radiation Angles
>Date: Fri, 10 Jan 2003 13:03:48 -0600
>
>Pat's observations are well made. I would go a step further with the
>comment that "G5RV" is an oxymoron, but that would make too many
>enemies!   <:}
>
>A true 3/2 -wavelength 20-meter G5RV using the 20-meter half-wave
>open-wire section and coax depends upon a fairly specific driving
>point impedance for the "antenna" for the multi-band matching - such
>as it is - to work. Varney designed the antenna to be a flattop.
>Erecting it as an inverted-V not only changes the pattern but alters
>the driving point impedance.  Both the pattern and the driving-point
>impedance are functions of center height and configuration.
>
>What effects that would have are speculative since they depend upon
>many unspecified and probably unknown aspects of the installation. But
>that is the only difference that I can identify, apart from the
>different pattern aspects of an inverted-V relative to a flat-top
>dipole. Also, note the added vertically polarized radiation off the
>ends of the inverted-V which is less with the flat-top format.
>
>If the "G5RV" is simply erected as a 51 or 102 ft length of wire,
>center-fed with ladderline to a tuner, then driving-point impedance no
>longer enters into the discussion and any difference in performance
>between inverted-V and flat-top configurations is attributed to the
>pattern difference. There is no longer any point in terming the
>antenna a "G5RV"  unless somehow lengths of 51 and 102 feet have
>earned permanent associated with that name.
>
>But, it should be noted that unless the antenna is in the order of
>1/2-wavelength high or higher at the lowest frequency of use, pattern
>considerations are largely academic. The typical antenna mounted at 30
>ft in the center and used on 80 and 40 will show little resemblance to
>the textbook free-space dipole patterns. It is largely non-directional
>in the azimuthal plane and concentrates its radiation more or less
>vertically. Feedline variations such as the trademark G5RV half-wave
>linear stub and coax, unless radiating due to common-mode currents,
>have no effect upon the overall radiation pattern shape.
>
>73/72, George
>Amateur Radio W5YR -  the Yellow Rose of Texas
>In the 57th year and it just keeps getting better!
>Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
>K2 #489  IC-765 #2349 IC-756 PRO  #2121 IC-756 PRO2 #3235
>
>----- Original Message -----
>From: "Pat W" <[email protected]>
>To: <[email protected]>
>Sent: Friday, January 10, 2003 10:16 AM
>Subject: Re: [Antennas] G5RV/inverted vee: Radiation Angles
>
>
> > There is nothing different about the G5RV than any
> > other dipole as far as take off angles at any height or
> > whether it is in a Vee shape.  THe lower the apex
> > height, the more ground loss(less gain).  THe steeper
> > the Vee angle, the more vertical polarization.
> >
> >  PS: I'm not sure what a 'shorty' G5RV is.  I think the
> > term is an oxymoron.
> >
> >  Pat W0OPW
>
>
>- - -
>
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>Larry Wilson KE1HZ [email protected]
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