Low Band DX

My 80/40m vertical During this time of low sunspots I got interested in how much DX could be worked on the lower bands. This led me to install a vertical antenna to improve my 80m signal. I first obtained an old hand-me-down AP8 trap vertical and I did make some contacts with it. But one of its low band traps was intermittent, and adjusting this many traps is a pain. Only wanting operation on 80 and 40 meters I considered the options.

I ended up deciding to get a MA8040 from Cushcraft. One factor is its top loaded design which should reduce losses associated with its matching coils by raising them well above the feedpoint. The configuration of the antenna is as follows: It starts with a straight radiating section for nearly 20 feet that is insulated from ground. There is no matching elements at the base. Elevated near the top are two coils in parallel, a smaller one providing a 40m resonance and a larger one providing a 80m resonance. Each of these coils is terminated with a small capacity hat. The 40m hat has only 4 spokes while the 80m hat has 8 spokes. There are no adjustments on the 40m section and it covers nearly the entire 40m with a decent match. Note this vertical is also approaching a full quarter wavelength size on 40m with only end loading thus it is close to ideal. On 80m there is an additional small vertical section above the capacity hat which is adjusted to a 50 kHz region of interest. Its length was configured to the instructions and it was nearly on my target segment (the bottom 50 kHz) on the first try. A little algebra based upon the graph in its manual got it right on the second time. This is a virtue when erecting a 27 foot tall vertical that is a little top heavy due to the coils and capacity hats!

The field of radials consists of around 30 wires between 3o to 50 feet in length. I had a large spool of aluminium wire with a plastic coating - perhaps #18 so it is a bit thin but not an issue for this application. Placing these on the ground in the fall they virtually disappeared during the next growing season.

My operating experience with this vertical is very positive. It gives some presence on both 40 and 80 meters with my 100 watt transmitter. DX has been worked on 80m across Europe to the Indian Ocean and middle east and a few contacts to Japan. Fed with 100 feet of RG-8 I can even use it across the entire 80 meter band with an in-shack tuner with reasonable results. I also found that is sometimes works better than my R5 on 20 meters in clearly having a different radiation angle and it also works very well on 30 meters.

I decided that 160m was the next frontier. Not having any options to mount a 160 meter inverted L meant I decided to try the MA160 which is a similar design to the MA8040. It stands at roughly 36 feet tall with a similar top-loaded design. It really stretches the design paradigm further as it has a much shorter electrical length that the MA8040. This shorter electrical length reduces the efficiency of the antenna because its desirable radiation resistance is smaller and perhaps not a huge factor larger than the ohmic losses in the top-loading coil. Still some DX contacts are made and it is much more effective in working DX (even stations a few hundred miles away also) than my low horizontal antenna.

In conclusion the 100 watt amateur station can work DX on the low bands with modest verticals. I have worked enough DX entities on 80m to now qualify for 5 band DXCC when I get the confirmations, and I continue to work additional countries when the pile-ups are not too large.

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