160 meters - or bust!
We start with my classic suburban lot (100' x 70') outside Boston which provides little room to build antennas for the lower bands.
A 100-foot dipole @25 feet above the ground (along the back property line) tuned well enough (through an MFJ tuner) for 80 meter WAS, performance on 160 meters was sub-par. It's easy to see why, since 25 feet is a fraction of a wavelength on 160 - meaning most of my signal was going up, not out, as we see in this EZNEC plot:
After exploring options including a sloper, inverted "U," several variations of an "L," some home-brew verticals with capacitive "top hats," as well as verticals sold by DxEngineering and MFJ, I decided to try an experiment suggested by Woody, WW1WW, to convert my 100-foot dipole, which was fed by twin-lead, into a vertical.
The EZNEC plot shows, with the vertical, I would achieve the goal of radiating most of the station's RF at an angle:
Radials, essential for a establishing a RF current return path to ground, would need to be installed. There were three challenges: 1. The small footprint of my property. 2. My house sits only ten feet from one side of my lot. 3. The only tall trees were also along the back end of the lot. So laying out radials would require some creativity. I began with four long radials at ground level:
It didn't work very well. Even with my MFJ tuner a decent SWR was impossible. To tune up a vertical only 25 feet high on 160 was going to require a loading coil.
Using EZNEC Woody modeled the antenna and calculated parameters for a base-loaded coil; 38 turns of 10-gauge wire coiled 2" to electrically extend the antenna. It would also eliminate the need for the balun. I constructed a coil using a short piece of PVC. A hole was drilled at one end for a binding post with banana jack (I was seeking an easy way to attach the radials.) An SO-239 was also installed.
The coil is connected to the center of the SO-239 on the inside of the tubeIt exits from the top of the pipe through a plastic cap. The cap and all holes were originally sealed using my wife's hot glue gun (a QST "Hints and Kinks") but, frankly, the glue did not provide a waterproof or lasting seal, so I had to redo with caulk. Now let's look at the performance of the vertical with the coil. I've included a brief reminder of what each measurement means...
This is the ratio of the antenna impedance (Z) to the transmission line characteristic impedance (50 Ω). (My buddy Doug, K1DG, says it's basically a measure of how happy the transmitter is.)
This is reactance, the opposition to alternating current due to a combination of capacitance and/or inductance (present in every antenna.) An antenna is resonant when capacitance and inductance cancel each other out.
This is radiation resistance, which measures the loss from the system (antenna, conductors, radial system). In this case, it is a reliable measure of how well the radials are performing as a counterpoise - an RF path to ground.
SWR and X were very good but R was over 50 ohms across the entire band. The four radials were a poor counterpoise and performance would suffer. More radials were clearly going to be needed, but you've seen the size of my property. Where could I lay them?
The answer was found in the work done by Rudy, N6LF in several QEX articles on verticals and radials which detail how elevated radials can be as effective - and sometime more effective, than ground-based radials. I ran a pair of radials approximately 3 1/2" off the ground, along the upper support of my fence:
These three plots show the original four radials (in red) and the two elevated radials (in blue). NOTE THE MFJ ANTENNA TUNER WAS NOT IN CIRCUIT. The SWR rose a bit but was still under 1.5:1 at the target frequency of 1.840 MHz.
Reactance was also lower at our target frequency.
What's most important is that R dropped almost 20 ohms across the band. An unqualified success!
Over the next month I experimented with several layouts of radials, including two on the top of the fence and another test with a "spider" of eight 16' radials (testing the theory that more radials, even short ones, will improve antenna performance.) None lowered R. In fact (and I challenge you to do the math - because I can't) both tests actually raised R across the entire band! In late August, 2011 I decided to try a couple of longer, ground-level radials.
The results, plotted in green, show a slightly higher SWR
Reactance did not change appreciably from the levels measured with 4 (red) or 6 (blue) radials.
The good news was R. The extra 2 radials reduced R across the entire 160 meter band by another 5 ohms, as low as the 30 ohm range around 1840 (the FT8 frequency)
...plus WAS & over 100 other entities
Table showing modes & DX distance
Country/Entity Callsign Grid Mode Miles
New Zealand ZL4AS RE43vt FT8 9494
Antarctica RN1ANL JB59 FT8 8792
Argentina LU8DPM GF03 FT8 5567
Cyprus 5B4AMM KM65 FT8 5265
European Russia RT6T LN05xb FT8 5125
Hawaii K9FD/KH6 BL11 FT8 5031
Crete SV9CVY KM25ka FT8 4915
Bulgaria LZ2WO KN22oo CW 4604
Ukraine UX1UA KO50em FT8 4470
Serbia YU1EL KN03ev FT8 4353
Belarus EU1WW KO34 FT8 4187
Bosnia-Herzegovina E77DX JN84ix CW 4182
Hungary HA7TM JN97 FT8 4171
Slovenia S51V JN86cm CW 4105
Croatia 9A1A JN75vn CW 4101
Lithuania LY7Z KO15we CW 4086
Slovak Republic OM2XW JN88ss CW 4079
Austria OE8SKQ JN76jn CW 4045
Czech Republic OL7M JO80cf CW 3977
Poland SP3DOI JO81vp FT8 3972
Finland OH1XX KP10ok CW 3886
Mauritania 5T5PA IL40li FT8 3774
Aaland Island OH0Z JP90we CW 3773
Italy IK4ADE JN54oe FT8 3758
Sweden SM3NRY JO99ah CW 3758
Switzerland HB3YAT JN46bt JT65 3758
Denmark OZ3AEV JO65gq JT65 3672
Spain EA3NE JN11an JT65 3652
Germany DL8GP JN39lh JT65 3634
Peru OA4AZP FI20ge JT65 3630
France F6ECI JN05sa JT65 3524
Morocco CN2CO IM64 FT8 3512
Belgium ON4GPE JO21nb FT8 3511
France F6GCP JN16gq FT8 3497
Norway LA7QIA JO29ta FT8 3335
Svalbard JW7QIA JO29ta FT8 3334
Portugal CT7ANG IM67 FT8 3334
ALASKA AL7TC BP51 FT8 3328
Canary Islands EA8AT IL38 FT8 3289
England G3BJ IO82om CW 3157
Wales GW5R IO82 CW 3112
Scotland MM0SJH IO89jb SSB 3042
Scotland (Orkney Is) MM0EAX IO89ka FT8 3031
Northern Ireland MI/3Z0X IO64pp FT8 2951
Ireland EI4KF IO54ue CW 2908
Iceland TF3DT IP04rr FT8 2547
Venezuela YV1KK FJ66wp CW 2512
Mexico XE1GRR DL80ho JT65 2418
Costa Rica TI7W EK80aa CW 2379
Trinidad & Tobago 9Y4/VE3EY FK90ik CW 2308
Azores CU2CE HM58xl SSB 2270
Madeira Is. CT3MD HM58qm FT8 2239
Nicaragua H7/RM0F EK72is CW 2237
Colombia HK1T FK20ox SSB 2203
Grenada J38XX FK92aa CW 2190
Barbados 8P9AE GK03fe CW 2154
Saint Vincent J88HL FK93jg CW 2119
Curacao Is. PJ2T FK52kg CW 2105
Bonaire Island PJ4A FK52me CW 2103
Honduras HR1LW EK84JB FT8 2090
Aruba P49X FK52al FT8 2076
Saint Lucia J68GU FK94mb FT8 2070
Martinique FM5CD FK94kq CW 2025
Belize V31YN EK58 FT8 1965
Dominica J79WTA FK95 FT8 1964
Montserrat VP2MSN FK86vq CW 1872
St. Kitts & Nevis Island V47KA FK87pg FT8 1816
St. Eustatius & Saba Is PJ5/SP6IXF FK87ml FT8 1798
US Virgin Is. NP2J FK77ps CW 1762
St. Martin FS/VA7XW FK88 FT8 1754
Puerto Rico KP4KE FK68kl CW 1687
Greenland XP3A GP44de FT8 1684
Cayman Islands ZF2CW EK99 LSB 1680
Dominican Rep. HI3K FK49ps SSB 1581
Turks & Caicos Is. VP5CW FL41aa CW 1495
Bahamas C6ANA FL24aa SSB 1315
Cuba CO8LY FK29bx JT65 920
Bermuda VP9/WW3S FM72ph CW 792
Jamaica 6Y5WJ EN82jl CW 619
Canada VA3WU FN03jc FT8 414
USA K1DG FN42ht CW 38
WAS completed in 2019
Mode Call Locator State Date
FT8 AL7TC BP15 AK 12/30/2019
JT65 KX4X EM62wi AL 11/16/2011
CW W5TZC EM34kh AR 11/14/2011
CW N7DD DM42lj AZ 1/28/2012
JT65 N6KMR CN91rn CA 12/31/2011
CW K0RF DN70jf CO 11/27/2011
SSB K1OQ FN41bp CT 8/24/2007
SSB N3PG FM28fw DE 5/6/2011
SSB WD3J EM70vk FL 5/16/2011
CW W1IBQ EM73um GA 12/28/2008
FT8 K9FD/KH6 BL11 HI 12/29/2019
JT65 W0MRZ EN42ea IA 11/16/2011
JT65 N7ESU DN17oq ID 12/31/2011
CW K9CT EM50aq IL 12/18/2011
JT65 W9THD EN71hp IN 11/23/2011
JT65 K0ASK EM28in KS 12/15/2012
CW W5MX EM77up KY 12/2/2011
JT65 W5ADD EM40wl LA 11/25/2011
SSB W1KQ FN42ip MA 8/24/2007
SSB K3WX FM19md MD 12/12/2008
CW W3HBM FN54vj ME 9/16/2011
HELL W8LEW EN72QP MI 2/06/2009
CW WI0S EN34ew MN 12/13/2008
JT65 K0TPP EM48rj MO 11/24/2011
JT65 N4UPX EM50jm MS 12/31/2011
JT65 N3RC DN45op MT 12/31/2011
CW W4MY FM15du NC 12/28/2008
JT65 ND0B EN07gn ND 3/5/2013
CW K0HA EN10lx NE 1/29/2012
CW K1BX FN43dc NH 1/11/2009
CW K2TTT FN20rw NJ 12/19/2010
JT65 AI5I DM65 NM 2/27/2013
CW K7CA DM26kc NV 12/28/2014
CW NN2L FN23ub NY 12/10/2008
CW KQ8M EN91hr OH 5/30/2010
CW K5CM EM25ir OK 12/4/2011
JT65 K7ZV CN82gk OR 1/4/2013
CW W8FJ FN20ic PA 12/28/2008
SSB W1XX FN41ej RI 2/27/2011
JT65 N4BAF EM84st SC 10/3/2011
JT65 WA0GMH Em19fa SD 1/29/2013
CW AD4EB EM65nt TN 12/2/2011
JT65 W5GW EM10ba TX 12/27/2011
JT65 KB7EEG DN31wd UT 1/4/2013
SSB W4NF FM18hq VA 2/27/2011
CW WB2MIC FN33jk VT 12/10/2008
JT65 K7LFY DN18bi WA 12/29/2011
CW NE9U EN54fl WI 12/3/2011
CW KE7/8 EM99 WV 1/21/2011
JT65 WY7FD DN74pm WY 12/10/2011