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160 Meters
Martin, AA1ON
Last Fall, immediately prior to the CQ World Wide SSB contest, I put up my first serious antennas for 160M.
The transmit antenna is a 1/4 wave sloper, a little over 140 feet of wire. This is attached to the center of a 50 ohm feedline run up the side of my tower to about the 75 foot level. The shield of the cable is directly attached to the tower at that point (I used a coax socket mounted on an aluminum plate, clamped onto the tower leg over a stainless steel shim). The wire slopes down towards my house (pointing towards Europe!!) and is about 15 feet above the ground at its end.
For receive, I installed a Beverage antenna. While these antennas do not have gain (in fact they actually have negative gain over a dipole), they do have a good front to back abd front to side signal ratio. Since the main problem hearing signals on 160 is QRN (atmospheric interference), the ability to eliminate interfering signals improves the signal to noise ratio and therefore readability of signals.
My yard is well configured for a Beverage. It is a long narrow yard (550 feet). The long axis of the yard points towards southern Europe and my house is located at the north eastern end.
Several types of Beverage antennas may be used. The simplest. a single wire Beverage, consists of a single wire, run between 5 -10 above the ground in a straight line. It is fed (via an impedance matching transformer) with coax at one end and the other end is generally terminated by grounding, often through a non inductive resistor. This version hears best in the direction away from the feed point. For my location, to hear Europe I would have had to feed this type of antenna at the far end of the yard and then run 550 feet of coax back to the house. Not a good plan !!!!
An alternative version, the two wire Beverage, solves this problem. In this design, two wires are run in parallel, about 10 -14 inches apart. At one end the wires are attached to a center tapped impedance transformer. the center tap is grounded. At the other end, a pair of matching transformers are used to generate two signal outputs, each of which is connected to a separate coax feedline. The two signal outputs are for the signals
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in the two directions, NE and SW, in which the axis of the antenna lies. By just switching from one cable to the other, either Europe or US and Pacific can be selected. It is therefore immaterial which end this antenna is fed, and I feed it at the NE end, about 10 feet from the road and 100 feet from my shack.
The wires are 14 gauge insulated, run between fence insulators mounted on 14 inch long wooden spreaders, nailed to trees about 10 feet above ground. The impedance transformers are mounted in plastic boxes at the two ends of the antenna.
I still have to install one 10 foot post (where there is a missing tree) to make sure that the wire runs more level, but the performance of the antenna is excellent. The ability to null out US stations and hear weak DX signals is amazing.
Note that this antenna is also not very expensive !!
I managed to work over 80 countries during the 160 M season. The band is most active during the winter months, when QRN is lower and signals stronger (few thunderstorms in Northern Hemisphere and longer periods when both ends of propagation paths are in darkness). While running full power does help, you can't work them if you can't hear them !!!
The high points of the season for me were 160 Meter CW contacts with
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ZS8IR (Prince Edward & Marion Islands), EM1KA (Antarctica), TOOR (Reunion) and VKOIR (Heard Island).
Receipt of the card from EM1KA, about 3 weeks ago, gave me Worked All Continents on 160M.
I'm looking forward to the shorter days.
Get Your Web Site in The Circuit!
Robert, N1UVA
Editor
Starting next month, The Circuit will be featuring the URL's of members personal web sites. So, if you have your own web site please drop me an e-mail with the URL and a short description would be helpful too. Your web site will then be linked from a special page on the FARA web site.
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