WiMo advertises the WY7023 in their interent shop as follows:

Source: www.wimo.com/en/wimo-wy-uhf-yagi-antenna

• Highest possible gain with high bandwidth and good side lobe and return loss. Thus the antennas are oriented to the requirements of serious VHF amateurs, who need a high performance antenna for long distance traffic and all modes of operation. The design principles of the Yagis were worked out with computer programs calibrated at NEC and verified by many test setups.

• Design current optimized (...). The yagis were designed for an optimal current profile. In older designs, there are jumps in the element current assignment, resulting in underutilized gain and poorer side lobe and return loss.

All this is clearly fine for the 2 m series of Yagis improved by DK7ZB, just not for the WiMo 70 cm series of 6, 10, 18 and 23 element Yagis. WiMo to the date of issuing this website (2026-10-30) does not provide radiation pattern plots for the WY7023.

Origin of the design?

The design of the WY7023 is twinned with what we find in Karl Rothammels (DM2ABK) Antennenbuch, Militärverlag der DDR, 8th issue, 6/1974: "Eine 18-Element-Breitband-Lang-Yagi", pg. 394, 395, fig. 24.8. The origin seems to be Spindlers Antennenbuch; Eberhard Spindler, VEB Verlag Technik Berlin, from 1968 ... . The directing element chain shows a relation to the NBS-Yagi with 0.308 lambda of spacing, see Peter P. Viezbickes 'NBS Technical Note #688', Yagi Antenna Design, 12/1976, therein table 1: 3.2 wl Yagi. This clearly is a pre-DL6WU design (inhomogeneous spacings, see DL6WU: Wirkungsweise und optimale Dimensionierung von Yagi-Antennen, UKW-Tagung, 1976).

Open a scan of the page in Rothammels Antennenbuch here .

In Rothammel it is spoken of modern design principles for long Yagis (1974), pioneering development work in the antenna industry, which uses such constructions in the manufacture of television antennas. 'Although wide bandwidths are not required for amateur radio use, they are not a disadvantage either if, as in this case, optimal gain is achieved.' (Which from todays point of view is, say quite debatable, as the Yagi as is, misses approximatly 1.5 dB in gain alone for its length).

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In early August of 2026 Eilert, DL9BDM asked me if I would have a pattern plot diagram of the WY7023, which I had not. Eilert had 4 of these Yagis in H-config on the mast and was bothered about their performance. Frankly, he purchased a 5th and measured the geometry. I subtracted the boom correction and simulated the design in EZNEC Pro2+ v.7.0.
Date of issue: 2026.08.15 .

4 x WY7023 at DL9BDM:

Photos on courtesy of Eilert, DL9BDM

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Analysis / Simulation

Current distribution WY7023

The current profile of the WY7023 is not optimised.



With a fix element distance of 203 mm equal to 0.29 lambda from D5 all the way to D21 it cannot be current optimised, contrary to the manufacturers advertise text.

Quote from the WiMo website:
The yagis were designed for an optimal current profile. In older designs, there are jumps in the element current assignment, resulting in underutilized gain and poorer side lobe (...).


Pattern at 432.1 MHz

 

At above 440 MHz, due to D1 to D5 or 6 or 7 being too short for 432 MHz, the Yagi finally comes to terms. But then the last 8 or 5 elements are too long:

 

WY7023_elev_plot_440MHz.png Performance Data

Specs: with 8 mm elements @ 432.1 MHz

Gain vs. isotr. Rad.  16.1 dBi
Gain vs. Dipole       14.0 dBD vs. '15 dBD' per WiMo description *
-3 dB E-plane         24.8 deg.
-3 dB H-plane         25.8 deg.
F/B                  -19.3 dB
F/R                  -17.8 dB
Impedance               50 ohms (200 Ohms + half wave line)
Mechan. Length        4035 mm plus boom end offsets
Electr. Length        5.82 λ

Stacking dist. h-pol. (100 percent per DL6WU)
top-to-bottom         1.440 m
side-by-side          1.560 m

*) A medium quality to date design delivers a gain of approximately 15.4 dBD on 4.0 m boomlength.

How many OMs have been looking up this design since Oct. 2026?





G/T analysis with AGTC Twain-JS: 4 bay of original WiMo 7023 modelled with folded dipole, at 432.1 MHz, at 100 percent of D_opt per DL6WU:

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First Aid

Modification Phase 1

WY7023 mod. ph.1 by DGYBN. Date of design issue: 2026-10-30

4 x WiMo WY7023 mod. Phase 1 by Eilert, DL9BDM

To copy this modification as much as seemed feasible of the original Yagi was kept. D1 to D5 need to be made from new tubes, D15 to D18 have differing positions, 2 elements in the front are removed. In order to help the WY7023 to an improved radiation pattern the impedance dropped, so that the original folded dipole has to be replaced by a K6STI style bent dipole to restore 50 Ohms at the feedpoint.

WiMo WY7023 mod. Phase 1, Current distribution and Modification Scheme

The current profile of the modified WY7023 Phase 1 is not fully optimised, yet shows much higher current on D1-D5 and a smooth downsloop towards the forward end.
The in between turmoil is due to sparing D6 to D14 in this phase 1 modification.

Radiation Pattern at 432.1 MHz

 

Performance Data

Specs: with 8 mm elements @ 432.1 MHz

Gain vs. isotr. Rad.  17.5 dBi vs. '16.1 dBi' of the original WY7023
Gain vs. Dipole       15.4 dBD
-3 dB E-plane         26.2 deg.
-3 dB H-plane         27.4 deg.
F/B                  -27.0 dB vs. '-19.3 dB'
F/R                  -26.9 dB vs. '-17.8 dB'
Impedance               50 ohms (200 Ohms + half wave line)
Mechan. Length        4035 mm plus boom end offsets
Electr. Length        5.82 λ

Stacking dist. h-pol. (100 percent per DL6WU)
top-to-bottom         1.465 m
side-by-side          1.531 m

Bent Dipole: DE(a) is the inner straight length and pos. on boom, DE(b) is position of tips and span width when bent

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Driver cell and bent dipole (K6STi style) by DL9BDM:

Dipole arms made from 10 x 2 mm aluminium strips: width ~312 mm.
Dipole arms made from 15 x 2 mm aluminium strips: width ~299 mm.



A simple symmetrising section may be made from a 3 x 1/4 Lambda line grounded at the far end with
N-flange-bushing and an aluminium plate and ferrite core added as close as possible to the DE,
see below.

WiMo WY7023 mod. Phase 1, VSWR and Return Loss

Comparison of Elevation Patterns: Original WY7023 and Modification Phase 1

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WiMo WY7023 mod. Phase 1, Stacking

Stacking Dist. at 100 percent of D_opt per DL6WU Formula

H-plane               1.465 m
E-plane               1.531 m

Gain vs. isotr. Rad.  23.30 dBi vs. '21.8 dBi' of the original WY7023
Gain vs. Dipole       21.21 dBD
-3 dB H-plane         12.4 deg.
-3 dB E-plane         12.0 deg.
F/B                  -27.8 dB
F/R                  -27.8 dB
T_ant                 78.5 K*   vs. '293.2 K'
G/T                    4.35 dB* vs. '-2.89 dB'

Theoretical numbers - these do not include phasing line losses
nor imperfections caused by H-frames or mast poles etc.
*) T_sky = 27 K, T_earth = 1800 K as in newer VE7BQH G/T table

G/T analysis with AGTC Twain-JS:

Comparison of Elevation Patterns:
4 x Original WY7023 and 4 x Modification Phase 1, both at 100% DL6WU stacking D_opt at 432.1 MHz;
Elevation plots on left, azimuth plots on right:

   

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Symmetrising 50 to 50 ohms feedline to 432 MHz Bent DE

The principle is similar to the 1/4 Lambda coax. Adding 2 x 1/4 Lambda or a half wave line does not change anything but allows
to form a gentle bow below the boom or until behind the Reflector. Follow practical construction hints on "Building a Yagi" page.

    

  Attenzione!     Take care when lengthening the coax, measure the actual electrical length instead of considering v-factors specified in a catalogue only.
                                      A good choice may be the diam. 5 mm PTFE coax RG-142 B/U: real resonate length (432.2 MHz as 3/4 Lambda) shield-shield is around 348 mm


  Find more information on Phasing & Matching Lines page






73, Hartmut, DG7YBN