As most of us know, the monoband yagi is by far the best antenna choice.

The majority of hams have unfortunately no room to put up several towers

for all the different monobanders. The average ham chooses a trapped

multi-band yagi. This antenna type allows him to be active on a number of

bands, but it has some drawbacks as well: loss of swr bandwidth, antennagain

and F/B ratio. Over the past years a number of commercial interlaced designs

have been available. These designs often put 2 bands on a same boom.

These interlaced yagis often give a good result and can be an excellent replacement

for the trapped yagis.

(The W4RNL web site carries an interesting article about these interlaced yagis).

Struggling to get a number of bands with good swr bandwidth and gain on a single

is to put a number of mono band yagis on the same boom, one in front of the other.

The first conclusion is that the boom length increases rapidly, especially if one

wants to cover 20 to 10 meters.The boom length was limited to 15 meters with

an option to shorten the boom to 12.8 meters. This should allow most of us to

reproduce the design. Those having plenty of room can go for the long design

18.3m (60ft) boom. The antenna covers the 20 to 10-meter bands.

The design has been done with the help of AO*, YO*, EZNEC/4*, STRESS*, and YAGI DESIGN*.

It gives full details about element lengths and spacing. The feedpoint impedance,

mono band yagis. These designs have been verified with the same software as

used for designing this antenna. Trapped yagis have not been taken into account

as these show less gain than their mono band counterparts and usually these

trapped yagis have unrealistic gain figure claims.

The basic calculation has been done for an antenna in free-space and all values are in dBi.

We don’t take into account the influence of the earth ground gain, and the reference antenna

is an isotropic radiator. (0 dBd = 2.15 dBi). If one takes into account the ground gain

(as most manufacturers do) the gain figures will be 4-5 dB higher.

However this in influenced by the antenna height.

The setup above real ground will change the radiation pattern.

The table gives the element length for a constant diameter (20mm) and the element spacing.

What is to expect from this antenna?

14.000 8.1 33.0-j4.1 26.8 1.26

14.175 8.2 30.9+j3.0 29.1 1.00

14.350 8.3 26.0+j12.2 25.9 1.44

18.068 8.1 20.9-j3.6 21.5 1.10

18.118 8.6 22.3-j2.3 22.3 1.00

18.168 8.6 23.5-j1.2 23.2 1.07

21.000 8.4 32.4-j7.8 21.1 1.27

21.200 8.5 34.2+j0.5 21.0 1.00

21.400 8.6 35.7+j8.1 20.9 1.25

24.880 8.5 10.7-j3.6 30.6 1.19

24.940 8.5 10.8-j1.7 30.6 1.00

24.990 8.5 10.8+j0.1 28.0 1.19

28.000 7.9 26.0-j7.2 29.7 1.47

28.350 8.1 26.9+j3.1 25.7 1.00

28.700 8.2 27.6+j13.9 22.6 1.48

This design has an almost constant gain over the 5 bands.

The swr bandwidth is excellent over the entire range with exception of 10 meters;

here it is limited to 28.8 MHz. Of course this swr is in reference to the matching frequency.

I’m sure that things still can be improved, but this may have a negative influence on swr

bandwidth and/or F/B. Another disadvantage of getting the last .5 dB out of the design makes

it more critical and less tolerant for small dimension errors (element lengths and spacing).

If you really want more gain, go for the longer design on the 18m boom. You will get the same

bandwidth and F/B (or even better) with higher gains.

A 15-meter boom too big for you? Perhaps this 12.8m antenna is the solution.

There will be one element less on 20m. The gain will drop to about 7 dBi, which is still good.

5.45 Reflector 20 0.00

5.2 Driver 20 2.00

4.15 Reflector 17 and director 20 3.05

4.02 Driver 17 4.00

3.8 Reflector 15 and director 17 5.00

3.395 Driver 15 6.20

3.02 Director 15 and reflector 12 7.30

2.91 Driver 12 8.10

2.78 Reflector 10 and director 12 9.40

2.55 Driver 10 10.25

2.355 Director 10 11.20

2.265 Director 10 12.80

Only 20m changes, they other gain figures remain.

14.000 7.2 33.5-j11.6 16.0 1.40

14.175 7.1 39.8-j0.9 29.1 1.00

14.350 7.0 45.3+j9.0 14.3 1.30

Do you have plenty of room? This 18.3m monster is the solution.

It gives you higher gain on the top 3 bands with an excellent bandwidth.

5.45 Reflector 20 0.00

5.2 Driver 20 2.00

4.9 Director 20 3.60

4.15 Reflector 17 and director 20 5.25

4.02 Driver 17 6.40

3.8 Reflector 15 and director 17 7.20

3.395 Driver 15 8.40

3.02 Director 15 and reflector 12 9.50

2.91 Driver 12 10.80

2.68 Reflector 10 and director 12 12.00

2.55 Driver 10 13.014

2.47 Director 10 13.816

2.44 Director 10 15.775

2.31 Director 10 18.25

14.175 8.3 34

18.118 8.3 21

21.200 8.7 23

24.940 9.6 38

28.350 10.0 29

This design made it at my home QTH.

The calculated specification seem to be corresponding really well with the on air performance.

Initial testing show an advantage as compared to a very large commercial multi band yagi.

The driven elements are all resonated in band.

The actual impedance of the antenna is high enough to allow different kind of feeding.

Personally I use a gamma match; the elements don’t need to be spliced up in this case.

One can choose isolated or non-isolated element mounting. The boom influence on the element length is minimal.

The boom element plate measures 200x100mm. If you wish to mount the elements non-isolated you can calculate the

The calculated influence is only a few millimeters for the 20m element. As this design is not critical, one can use the isolated element lengths.

Each element has to be as strong as possible for a minimal windload and weight so we use tapering.

Most of the available antenna design software programs allow calculating the taper. Only a few allow calculating the element strength.

Initially I used STRESS*, this software is used by the former Telex/Hygain company.

Afterwards I used a Belgian product, YAGI-DESIGN* by ON4UN. This package can calculate in all circumstances the taper of an

element that complies with a wind survival. This for the lowest possible weight and windload. The element sag is also calculated.

The calculated minimal wind survival is 160km/h, (100mph). The antenna is mounted on an 80ft tower on top of a 300ft hill here.

Parameters: EIA-222-C pressure 30lb/sq ft at 86mph.

The table gives us element diameter, wall thickness, length, half element weight and length. The elements will be adjusted with the tip end.

Some of these elements are telescopic on the inside. All of the 20m element consist of 3 diameters.

The wind load of this half element is 0.13m². The weight of this half element is 2.6kg

Element sag is 20.5cm. The tip will be adjusted.

Element 1 : 2567mm 2570mm

Element 2 : 2309mm 2312mm

Element 3 : 1998mm 2000mm

1750x25x2.5 **x19x1.5

The wind load of this half element is 0.084m². The weight of this half element is 1.85kg

Element sag is 8.4cm. The tip will be adjusted

Element 4 : 4222mm 4224mm

Element 5 : 4053mm 4056mm

Element 6 : 3852mm 3854mm

The wind load of this half element is 0.074m². The weight of this half element is 1.2kg

Element sag is 6cm. The tip will be adjusted

Element 7 : 3450mm

Element 8 : 3082mm

Element 9 : 2957mm

750x25x2.5 **x19x1.5

The wind load of this half element is 0.059m². The weight of this half element is 1.1kg

Element sag is 3.5cm. The tip will be adjusted

Element 10 : 2845mm

Element 11 : 2583mm

Element 12 : 2364mm

Element 13 : 2264mm

44.55 kg and a 2.20 m² windload.

If you choose the variant 1 you will have 0.26m² less wind load and will gain about 5.2 kg.

The actual weight of the antenna is function of the choosen boom diameter, the mounting plates and all related hardware.

My antenna uses a 4 inch boom and the weight is around 60 kg.

For an output power of 2000 watts one should get capacitors handling 300 volts and 6.3 amps current.

Is it all worth the trouble ? Looking at the actual cost, YES. The price should be below $800 (US) for the 60ft design.

The design is non-critical can can be easely reproduced. The gain is excellent and you will have a big signal on the bands.

However, an antenna this size requires a strong tower and big rotator. If you have the tower and rotator for it, its an excellent choice.

A comparison with some commercial mono band antennas gives you a idea about the performance of this antenna.

The values indicated are NOT those from the manufacturer, but those calculated with the design software used for this antenna.

Only this procedure gives an objective view on the gain, since all gains were computed in exactly the same way.

310-08 7.17 1.31-1.46 3el 10m on 2.3m boom

103BA 7.51 1.53-2.01 3el 10m on 2.3m boom

153BA 7.68 1.45-1.68 3el 15m on 3.5m boom

315-12 7.54 1.49-1.45 3el 15m on 3.6m boom

320-16 7.21 1.27-1.38 3el 20m on 4.7m boom

203BA 7.17 1.22-1.20 3el 20m on 4.8m boom

20-3CD 8.09 2.03-2.90 3el 20m on 6.0m boom

10-4CD 8.58 1.63-1.79 4el 10m on 4.8m boom

412-15 8.40 1.09-1.09 4el 12m on 4.4m boom

415-18 8.24 1.41-1.38 4el 15m on 5.4m boom

417-20 8.52 1.08-1.11 4el 17m on 6.0m boom

204CA 8.25 1.49-1.47 4el 20m on 7.8m boom

420-26 8.60 1.28-1.37 4el 20m on 7.8m boom

20-4CD 8.54 1.78-2.20 4el 20m on 9.6m boom

510-20 9.75 1.49-1.53 5el 10m on 6.0m boom

KLM510 9.21 1.33-1.43 5el 10m on 6.1m boom

105CA 8.38 1.42-1.23 5el 10m on 7.2m boom

155CA 9.70 1.49-1.62 5el 15m on 7.7m boom

205CA 9.23 1.43-1.96 5el 20m on 10.4m boom

KLM520 9.43 1.66-1.25 5el 20m on 12.8m boom

This design is a valuable alternative for a 4 element monoband yagi, taking into account the gain and swr bandwidth.

It is obvious that some improvements can be done, depending on your specific needs. Perhaps you need less bandwidth.

I tried to have a broadband yagi with gain figures close too or better than the common 4 element moband yagis.

The real gain, with associated radiation angle is given in next table.

14.150 13.55 dBi @ 12°

18.118 13.64 dBi @ 10°

21.200 13.74 dBi @ 8°

24.940 14.20 dBi @ 7°

28.400 13.77 dBi @ 6°

AO and YO written by K6STI.

Comparison of this design made by W4RNL with EZNEC4 shows very similar results to those obtained with AO.

The W4RNL site contains lots of valuable antenna information and really is worthwhile visiting.

My sincere thanks to L.B. Cebik for the verification of this design and the information available on his website.

YAGI DESIGN was written by ON4UN and covers all mechanical issues of antennas. It’s a DOS based program,

and is extremely easy to use. I wish to thank John for his help as well. Those wishing to obtain this program can

always contact John, ON4UN

STRESS Hygain/Telex.

(a 50 MHz yagi with 15.0 dBi gain)

Having lots of space for antenna I started out with a design for a long yagi, 9 elements on a 15 meter boom.

I did not choose to go for a folded dipole, but rather stick to a minimum value for the feed impedance.

Table : Element length versus position. Element diameter is 12 mm.

A total gain of 15.0 dBi, this out performs the DL6WU designs by a few tenths of a dB.

It outperforms the commercial M2 design as well with 0.15dB.

(6M9KHW !, the older 9 element, a 2 WL, is 1 dB down)

(a 50 MHz yagi with 14.1 dBi gain)

If one wants a very simple feed like a folded dipole with a 4:1 coaxial balun, you can opt for for this design.

Lower gain (14.1dBi) but excellent match.

This very 'easy' design has a free space gain of 14.1 dBi. The element diameter is 12mm.

The values given in the table do not take into account the influence of the boom.

There are some formulas to calculate the influence of the boom on isolated elements going through it.