Sunday, June 12, 2011

Full 1/4 wave vertical for 40m

Full 1/4 wave vertical for 40m

Seeing nice DX-stations on a cluster that you cant here frustrates HI. For now on I was working with a dipole at 6m AGL. This worked fine for 80 country's on CW-40m in 6 months, but the further stations where mostly not hearable even if an other ON station worked them. So I decided to take the risk to build a vertical.

Several articles and gaining experience from other OM's, further on, my strategy was to build a 10 m high Alu thing.

The construction

To construct the antenna, I used 6 tubes of each 2m length. Starting at 10mm diameter for the top and ending with 36 mm at the foot. To assemble the rods I made a cut in the top of each tube. The next tube fits in the previous one and with a inox ty-strap I fixed the tubes one on another

See the picture at the right.

Here under you can see all of the the parts to assemble
the antenna. The dimensions depends on what you can
on the marked or in the shops.

bulletA waterproof connection box
bulletTwo U bolds fitting round the foot tube
bulletTo metal strokes to fit over the U-bolds on the inside and on the outside of the box.
bulletA longer metal strip to strongen the inside of the box there were the box is mounted on the support.
bulletAn L-Form with a dickness of 5mm to support the whole antenna on the ground rod.
bulletA small winkel with in one leg a hole to mount on the support and in the other leg the necessary holes to mount a PL-connector.
bulletA PL-Connector and a solder lip to connect to the antenna.
bulletTwo rings to mount the support ropes on the 1/4 wave rod. In my particular situation is was necessary to support the antenna two times. (Tip: do not support the antenna on two equal distances or the antenna will resonate by winds an break down)
bulletNon-conducting rope to support the antenna.
bulletSome ty-straps to fix the antenna tubes one in an other.
bulletA copper connection strip to connect the radians.
On the pictures beneath you can see how to assembly the whole thing. Both view here are upside down. The Alu tube you see is the feet of the antenna. All parts are well covered with silicone to give the water no chance. before mounting the metal strips, cover the holes in the plastic box with a lot of silicone
Here you can see how the plastic box is mounted with
the L-profile on the Earth-rod, and how the antenna is
connected to the inner conductor of the PL-plug. I left
place in the box so that I can mount in the future a coil
for use of the antenna on 80m ?160m?

The top of the antenna is protected by a rubber top (used to protect the carpet from chairs holes).

The total length of the antenna is 10m exact. The 5 top tubes shifted in each other by 20 cm and the Fifth one by 1.2m in the final feet tube (so we have 2+0.8+(4x1.8) =10M This way there was enough space to tune the antenna on frequency.

The last step is to put as many as possible of radians on the earth-rod with the best possible length.

Then, connect the antenna to the transceiver on minimal power and tune the antenna for maximum radiation by means of a field strength meter. Watch the VSWR, he has to be good to when the antenna is in resonance.

Finally, go to high power and work half of the world.

In Two months I worked Argentina, Uruguay, Brazil, Trinidad, Aruba, Antigua, Cuba, Belize, Malawi, New-Zeeland, Thailand, Hong-Kong, Taiwan and Eastern islands. - Keep your dipole, its nice if you can switch en experiance the differance between the antennas.

Have a lot of building fun


Anonymous said...

I find your site and information. very useful.
I always have used vertical antennas.
73 and good dxing

N3TEE said...

Hope to work your station one of these days.
73 Shawn, N3TEE