On the 160 Vertical page I introduced you to the issues I faced getting on 160 meters with my small suburban lot. This page presents the story of how I successfully set up a vertical antenna on the Gentleman's Band.

It began in 2011 when my then co-worker Woody, WW1WW (tired of hearing me whine about my station's poor 160 performance) suggested converting my 100-foot dipole into a vertical by twisting the leads of the twin-lead together and feeding them into a balun. 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:

Aerial view of the QTH showing the four radials(white, orange, yellow, and green lines) and the location of the former dipole (dotted red line) now acting as capacitive "top hat"
   

View of the former dipole, now a vertical, showing locations of the four original ground-based radials
 
 

The MFJ Balun secured - and grounded - to a ground rod. RG-8x coax feeds into the shack and the MFJ tuner.

So how did it work?
 
Not well at all. Even with the MFJ tuner a decent SWR was impossible:

Plot of 160 meters adjusting the MFJ tuner for best SWR every 25 kHz

 38 special

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 tube

 

It 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 had to redo with caulk.

 
 

The new coil, installed, with black tape wrapped around the 10ag wire.
 

 
Readings were taken with an MFJ-259B loaned by Erik, KE1V (thanks!)

Before we look at the results... a brief review.

SWR	X	R
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.

With four radials here are the plots of SWR, Resistance (R), and Reactance (X) across 160:

 

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?

Nurse... elevate me

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:

The red lines show where the first two elevated radials being tested are attached to the fence

This annotated aerial shows where I hung the elevated radials around the property:

The length of the longer radial is a bit less than 130 feet, or 1/4 wavelength at 160 meters.

Check out the plots for SWR, R, and X, which include the original four radials (shown in red) and the addition of two elevated radials (shown 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. X was lower at the target frequency. What's most important is that R dropped almost 20 ohms across the band. An unqualified success!

Some other interesting things happen with the addition of the 2 elevated radials, like a steeper bend in the plot of X (an increase in Q.)  But wow look at R - as much as a 20+ ohm difference from the 4-radial configuration. Outstanding.  But can we do better?
 

8 is Enough?

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:  

Location of the additional 2 radials

The results, plotted in green below, show a slightly higher SWR with X not changing appreciably from the levels measured with 4 (red) or 6 (blue) radials.  But there was good news in the data as R shows the extra 2 radials reduced R across the entire 160 meter band by another 5 ohms, as low as the 30 ohm range near the lower part of the band, precisely in the targeted area of the band (CW & FT8). 
 

 

 

It appeared the point of diminishing returns had been reach, with respect to the number and placement of radials. By then it was winter 2011/12 the best time of year for operating 160. During the next few months I contacted 41 states and 9 new countries, a HUGE improvement over the dipole.

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May 2012 Update

The vertical was great, but I missed the dipole and its performance on 80-10 meters. To allow both vertical and dipole operation I added a relay, mounted on top of the loading coil, so I could switch the antenna remotely, from the shack.