Minggu, 04 Maret 2012

HB9CV - 2 Element Yagi for the 11 meter band

The idea is to get an small antenna, this is a great solution. The HB9CV antenna is smaler than a 3el. conventional Yagi but you get the same gain and caracteristics. I had to change The original design because it probably was designed for the 10m Amateure band.

I built the antenna for My local radio-friend,- 21BD012, Roger is now using the antenna on a daily basis. (Updated information: The antenna was torn down in a winter storm in 2004) I trye to describe the building process in simple steps,- but first about the antenna principle.

Main design principle
The HB9CV Antenna is actualy an Log-preiodic ARRAY in it´s simplest form,- The transpose / cross-feed system feed the RF-Signal onto the two matched driven elements in 180dgr phaze,- This is the "key" to this antenna design.
Image3 shows the complete HB9CV Antenna from a "Top" View,- Notice that the Gamma rods used for Feed/Match is placed in oposit on each element.

Image2. -HB9CV Top View

Image3. -HB9CV Dipole

Each of the two elements is made out of four parts: (Numbered in blue)
  • 1. Center section - 16mm Dural-Aluminium tubing 3m in lenght
  • 2. Tip sections - Two per Element,- One at each end. To extend the element to the total lenght
  • 3. Aluminium bracket,- with U-Clamp for mounting each element on to the boom.

You also need two identical gamma maching roods,- one for each element,- To Make One gamma-rood, you need the following stuff (x2 to make both!: (Marked with red letters)
C. One Aluminium rood about 1.1m long and with diameter 10-12mm
D. SWR Adjustment plates,- made out of two pcs. of 3mm aluminium about 100 x 25mm,- attached between Dipole element and gamma-rood with two screws and nuts,- so it can be moved for SWR adjustment.
E. Distances / Insulators,- made out of tube-clamps and nylon,- se photos.

A. Feed point - Use a 275pF serial capacitor to connect The Center core of the Feed line here. The Cross feed to the other element is also connected here.
B. Grounding screw,- to connect sheild from coaxial feed line.

Electrical principle

Image4. -HB9CV Electrical principle
The text Refere to Image 4:
The gamma rods (Red) on the two elements (Blue) is connected with the (Yellow) Cross feed cable. The SWR-Adjustment is made by moving the (Green) SWR-Adjustment plates along the (red) Gamma rods.

The Feed-Line (Yellow) is connected via a 275pF Capacitor to the (Red) Gamma-Rod on the shorter Front element,- at the same point,- the cross feed coaxial-cable to the rear Element is connected.


Image5. - Coaxial Cable connections

Element1 with feed-point capacitor and matching-rood connection

Element2 with cross-feed cable and matching-rood connection

1 komentar:

  1. Saya sudah membuat antenna ini dgn hasil yang memuaskan,SWR saya dapat 1 : 1.1 di Frek RAPI dan 1 : 1 di Frek DX ( 27.555 ) dgn tidak banyak melakukan tuning Kapasitor yg saya pergunakan 271 pF,karena di tempat saya tdk ada yg jual 275 pF