Saturday, December 03, 2011

70Mhz antenna - HB9CV Review

At last! Some stations to work on 4m with my new HB9CV!
Last week was the Tuesday evening activity night contest on 70Mhz. These don't seem to happen every month, so I have had to wait for this one to come. I have always liked 4m, years ago I had a Pye Ranger AM set with it's all valve line up. I used this for quite a while until I built a 4m Transverter which I am still using now. I had lots of fun during VHF NFD back in 70's and 80' when I always opted to operate of 4m.

4m and 6m tranverter with the old Yaesu FT101E and HF Z-match. This is my present set up for 4m.
For a while I used a 2 element band 1 antenna which was fixed on the side of the house, eventually, it fell apart, so I was qrt on 4m for a long time.
I bought the HB9CV from Moonraker, which arrived after first being sent a 2m, 4 element instead of the 4m 2 element. This was then replaced with correct yagi but minus the extension rods required to tune the antenna. After an e-mail to Moonraker the rods were dispached separately. The antenna was easy to put together, but the instructions are not very clear, you have to work out yourself how to fix the driven element. Inside the the terminal box is an airspaced 'beehive trimmer' - not seen one of these for years! The trimmer is used to tune the antenna to obtain best SWR. This I found quite straight forward. This antenna has a rear mounting bracket, which is fine, but the supplied clamp was poor and even when fully tightened the antenna keeps dipping down. The extension rods have to be tightened with the screws fitted, I still don't understand why this kit has extension rods, why couldn't they make it all in one piece? You need lots of vaseline to keep the screws from rusting, they are stainless, but only coated.
The HB9CV is mounted on a rotator, so my first thing was to check the Buxton Beacon on 70.000Mhz. This was coming in well over s9, very strong!

On Tuesday conditions were poor, but I still managed to work 16 stations, my furthest being down in the midlands with just 5 watts. I like this antenna, it was quite sharp and had a good front to back ratio. I guess the HB9CV is actually a 3 element yagi with the driven element bent between the director and reflector. It is quite a neat antenna which doesn't take up much room, but performs we
It is a pity that 70Mhz is not used as much as it should, when conditions are good you can work long distances. I remember once working stations on cw during a good Aurora.

I found this design on the internet and used it to make a 432Mhz version of the HB9CV. Thank you to the German station that made the design. It works perfectly!
For 70Mhz just put in your own measurements (lambda is the wavelength of the band eg: 4 metres, 2 metres, 70 centimetres)

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