40m 1/4 Vertical [Epic] Antenna

So the antenna farm at M1BXF QTH just got larger with the addition of a 40m 1/4 vertical.  I’d been thinking about this antenna for while as verticals are good for DX, more in this in a moment, and require little space to erect, but does need space for radials.

The antenna is based on a 10m fiberglass pole for the vertical element support, 17 radials and a clothes line ground screw to hold it up.  I ended up with 17 radials as I cut one for length then made a ‘jig’ which allowed me to make 4 at a time after, so I made 3 x 4 in the jig + the one I had…  I put screws in at each joint of the 10m pole also so there was no chance in it falling down into itself.

CIMG7401

As you can see I erected it near some trees, this is mainly to make it less noticeable in the direction of the house which is through the trees as it were.  To help make it blend in further I painted the pole Hamerite ‘highland green’.

The radials all connect to a circular copper bar I made which goes round the base of the antenna with a short wire going to the ground of the feed-point.  The radiating element ends in a circular crimp, another is also soldered to the SO-239 centre pin so the method of connecting the vertical radiator to the feedpoint is with a nut and bolt, click to enlarge.

IMG_20110605_151120 CIMG7403 

Once all was connected up I felt like tuning it, this only took 2 attempts to get it to VSWR 1.07 @ 7.1MHz as you can see in the first plot, the second plot shows the other resonances upto 60MHz so it is usable on 15m (21MHz) also, albeit with an ATU as the VSWR minimum is outside the 15m band.  At first the VSWR @ 7.1MHz was 1.2:1, getting it lower was me being picky.

4m_vert_40m_only 4m_vert_1MHzto60MHz

So why is this antenna epic?  Well 5 minutes after connecting it up and tuning through 40m I heard VK7AC working a pileup, 3 calls later and we managed 58/57 either way so the first QSO on the antenna was with Australia (Tasmania) @ 17255km, EPIC!!!

3 Comments

  1. Dave

    Hi
    I work at sea ( marine engineer ) and have a vertical cut for 40m going up to the mast, its at about 45 deg angle, so the top of the vertical is prob about 150feet above the waterline, the ground plane is the ship so its nice and big (all 35,000 Tonnes of it ), and also being out at sea its lovely and quiet with no local computers, cars and all the other million appliances that make noise when operating from home. My dad lives in the south of france and id like to make him a 40m vertical as he has plenty of space for radials in the garden. Could you tell me where you got your fiberglass pole from?
    Like the web page and construction ideas, my main interests are also eme, weak signal, and satellites but suffer from a small garden but have nice neighbours,
    Dave

    Reply
  2. chris

    hi,good to see people building there own antennas,i have been running 40m phased verticals for 3 years they aregreat,i started off with ground mounting but took advice from an american friend and raised the feed point with elevated radials,you think your vertical is good now try elevating it it makes an amazing difference and you only need 4 radials.Keep up the good work and enjoy the hobby,best 73s de chris GM4ZJI.

    Reply
    1. m1bxf (Post author)

      Hi Chris, Well I try and build as much as I can, antennas included although I must admit a local ham G4ERO has build my 5 element 6m/4m duoband and 9 element 2m YU7EF antennas, but he had more time than me! I understand about elevated radials, my issue is the antenna is situated next to the ‘party’ are of the garden where I have a gazebo and a fire pit so having anything elevated would end up being trashed… For my activity level on 40m it’s fine for just now but thanks for the comment 🙂

      Reply

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