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BigIR MK III Vertical with 80 meter coil

28 April 2008.

I received my BigIR on October 8, 2007.


The assembly went well enough despite the skimpy documentation.  There is an error on page 5 of BigIR MK III instruction manual.  Figure 1 shows two diverter extension tubes but the text accompanying the figure says that there a three pieces.  I only found two and once you figure out the assembly you'll discover that two is the correct number.  Somewhat worse is the front cover of the 80m Coil Kit instruction manual.  It does not show a ground connected to the 80m coil kit while page 6 of the manual makes it very clear that the ground should be attached to the 80m coil not the element housing.  The correct installation is shown in the first picture on the right.


It was not immediately obvious which end of the mounting pole should be in the ground.  I simply tried both ends into the element housing and only one fit so I kept that end outside.  I got a little carried away with minimizing the distance of the element housing about the earth.  I am using a DX Engineering radial plate.  I set the mounting pole into the ground with 9 inches remaining above the ground and found it a bit difficult in some cases to put the bolts into the place for the radials.  This was complicated by the fact that due to my location the vertical is mounted on a slight slope.

I decided to run 30 50-foot radials.   This seemed like a reasonable balance of length, losses, and number of radials.  The radials were installed, simply laying them on the rocky adobe ground of my location, over a period of several days with some attempts at doing this symmetrically so that I could use the antenna in between installations.  Why did it take a week or so to install?  Just look at the picture to the right and imagine running radials through this growth. 

Since I could tell the difference in tuning and SWR when I went from 24 to 30 radials I'm now thinking of going all of the way to 60 radials -- and making the next 30 a full quarter wavelength on 80 meters.  But I'm certainly going to take my time and let the cuts and scratches (broken piñon branches are sharp!) heal.

One set of guys was used to increase the wind resistance.  After several attempts to find suitable anchors in this soil I finally purchased some clamshell anchors from a tree supply and drove them in.  They work great.


The antenna does well on all bands including 60 meters.  The SWR is low enough that I don't need to use the antenna tuner in my Icom PW-1 amplifier (which is a good thing since it is broken).  It has taken a while to adjust the elements lengths on all bands to get optimum SWR.  The MFJ 259B antenna analyzer has been a big help with this.

It played well on 40 and 80 during the CW Sweepstakes -- I worked pretty much everything that I could hear and had productive "runs" on both bands.

During the CQ WW DX contest on SSB it did well -- working all continents except Europe which is extremely difficult from my location.  Something about a 10,000 foot peak only 3 miles away affects propagation in that direction.

In a SSB North Americcan QSO party I worked Georgia on 75 in the mid-afternoon.  The other station commented that he couldn't believe that I was S9 at that time of day.

The antenna works so well on 30 meters that one station accused me of violating the power restrictions during a pileup.  I wasn't and said thanks for the compliment.

I've worked Hawaii and several Caribbean and Latin American stations on 60 meters.


Well, it isn't very good.  I've already mentioned two of the assembly manuals.  The operating manual is worse -- lacking much specific information for the verticals and instead concentrating on the beams.  For instance, it is not particularly clear how many "modifications" in each band need to be made to ensure uniform SWR across the entire band when using the 80 meter coil.

It is also interesting to note that the documentation that can be downloaded on the web page is in color while the manuals supplied with the radio are black-and-white.  Unfortunately the website manuals were not always the current revision.


A bug in the microcode that kept forgetting the 3/4 wave setting was fixed by SteppIR sending a new chip.  I'm happy with the antenna and now that the snows are gone will start on some more radials.