A 1.6 l-yagi for the IARU-Region 1 2m-band (by DK7ZB)

While looking for a good design for a portable, not too big in size, all-purpose-yagi for the 2m-band here in IARU Region 1, I found this antenna in the german magazine ‘funk’ issue 11/98. The designer DK7ZB meanwhile did a lot of antenna work and published some very interesting antenna designs on HF, VHF and UHF. I choosed this specific antenna because of its allround properties:

  • extremly clear pattern
  • covering the whole 2m band
  • good gain

The first version I built was a 10mm version (driven element 12mm) with the original element holders for keeping it portable (dismantable).

The general datas of the yagi are:

Gain 11dBd @ 145 MHz
Boom length 3,3m (1,57 l )
F/R >26 dB @144,3 MHz
>25 dB @145 MHz
~ 20 dB @ 146 MHz
Impedance 28 Ohm
Element # 7

The goal was to build an antenna that doesn’t need a support structure, provides good datas and is easily handable at portable operations.

The boom is a aluminium square tube of 20 x 20 x 1,5 mm. All elements are aluminium tubes 10 x 1 mm except the driven element, that’s a 12 x 1mm aluminium tube.

As common use the elements are mounted insulated. I used the original suggested commercially available polyamid holders obtainable from [1]. For a detailed view look at a holder picture.

These holders are made from polyamid and are UV resistant. I am using only the bottom part. With a 3mm stainless steel screw the elements are hold in place under normal conditions. Although grounding the elements should detune them, the designer DK7ZB said with 15 x15 or 20 x 20 mm boom on 2m/70cm you can use free space data without disadvantages.

The mechanicals datas were given for parasitic element diameters of 4, 6, 8, 10 and 12mm (driven element always 12mm ! ). I only realized the 10 mm version ( and soon maybe a light weighted version with 4mm isolated mounted elements through the boom. This antenna doesn’t allow dismantle the elements, provides however very low weight). Maybe a compromise in terms of weight and portability/dismanteling is the use of 6mm aluminium tube elements.

Mechanical datas:

Element Position [mm] length free space 4mm length free space 10mm
R

0

1024

1016

DE

360

980

980

D1

600

963

944

D2

1150

937

914

D3

1830

920

895

D4

2635

919

894

D5

3260

908

881

Note: The driven element is a straight split dipole with a lenght of 980 mm built from 12mm x 1mm aluminium tube

Inside the split dipole is a acryl glass rod to hold the dipole legs in place. Other materials may also be used like polyamid, PVC even bamboo was used (not recommended !).

Don’t forget to ground the RF-socket at the boom to avoid currents on the braid of the coax cable !

dipole + RF socket A close look at the feed (early stage)

element fixing A close look at the element holder

Tinggalkan Balasan

Isikan data di bawah atau klik salah satu ikon untuk log in:

Logo WordPress.com

You are commenting using your WordPress.com account. Logout / Ubah )

Gambar Twitter

You are commenting using your Twitter account. Logout / Ubah )

Foto Facebook

You are commenting using your Facebook account. Logout / Ubah )

Foto Google+

You are commenting using your Google+ account. Logout / Ubah )

Connecting to %s