(01/09/2023) I've been playing with antennas for many years and enjoy seeing what works and what doesn't.  In fact, many of my experiments are in my Notebook Series.  On this site, I take a look at the G5RV with and without a 30 meter element hung under the main element.  I also look at the ZS6BKW using the same 30 meter element.

The EZNEC (.ez) files are available at the links below for you to review.  I'm not an expert, but these simulations will give you an idea of differences with the added 30 meter element and what to expect.  The antennas are mounted as inverted-V's 30 feet at the apex and 10-11 feet at he ends.

In reviewing the plots, it appears that the 30 meter element is too short, or is interacting with the main element.  Additional work needs to be done using EZNEC to see if the 30 meter dip can be moved more in the direction of 10mHz.  The plots, as shown, are fairly close to following my very old Autek Research VA1 RX Vector Analyst.

    Download    1) G5RV without added 30 meter element
    Download    2) G5RV with 30 meter element
    Download    3) ZS6BKW without added 30 meter element
    Download    4) ZS6BKW with 30 meter element

The sole purpose for these designs was a need to have 30 meters (and the other bands) available and tunable using auto "L" tuners.  I was mostly interested in 80 through 20 meters.

(01/17/2023) Today, I used EZNEC to see if I could move the dip closer to 10.1 MHz for the G5RV with the 30 meter element.  First, I dropped the end of the 30 meter element a couple feet away from the main wire.  (This is the end away from the center insulator.)  This made the dip move closer to 11.5 MHz.  Not in the direction I wanted to go.

I also tried lengthening the 30 meter element by a foot, but keep the 6 inch separation along the wires.  This worked, but I probably could have added 1.5 feet.

(01/19/2023) I modeled the modified G5RV this afternoon making the following changes in wire lengths. The 30 meter element is 25.5 feet per side and the length of the main element is 51.5 feet per side.  The feed-line is the same as the other modeled G5RV's.  Here is the EZNEC (.ez) file.

    Download    1) G5RV with added and lengthened 30 meter element

The plot is at the bottom of the page.  The dips are at 3.5, 6.75-7, 10-10.25, 14, 20, 24.25-24.5 and 28.25-28.5MHz.  Note, I have not built this version of the antenna, but if you do, there should be plenty of wire to play with.  The wires do seem a bit long to me, but this is just a model.  I am still using the original.

G5RV configuration:
    1) Antenna Wire CERRO VINYLON-1 NYLON 14 AWG 12/06MM (Stranded)
        ~ 2 ea 51 ft lengths top elements
        ~ 2 ea 23.5 ft lengths for bottom elements
    2) 6 inch separation between top elements and bottom elements
    3) 31.5 ft Wireman 552-16 Stranded Window Line 16AWG .91VF
    4) 8 ft run of M17/128-RG400 MIL-C-17 27478 Harbour Ind Coax
    5) Current balun (common mode choke)
        ~ #31 Fair-Rite (biggest clamp-on) core
        ~ Wound with RG400 Manhattan Commercial 12515 coax
        ~ The length of coax wrapped through the core should be added to item 4).

ZS6BKW configuration:
    1) Antenna Wire CERRO VINYLON-1 NYLON 14 AWG 12/06MM (Stranded)
        ~ 2 ea 46.8 ft lengths top elements
        ~ 2 ea 23.5 ft lengths for bottom elements
    2) 6 inch separation between top elements and bottom elements
    3) 39.1 ft Wireman 552-16 Stranded Window Line 16AWG .91VF
    4) 8 ft run of M17/128-RG400 MIL-C-17 27478 Harbour Ind Coax
    5) Current balun (common mode choke)
        ~ #31 Fair-Rite (biggest clamp-on) core
        ~ Wound with RG400 Manhattan Commercial 12515 coax
        ~ The length of coax wrapped through the core should be added to item 4).