160 meters - or Bust!NOTE: I am pleased to offer a download of the slide deck I use for my talk on this project, which I've given to a couple of local ham clubs. If you are interested in booking me to speak and you are not in New England we could set up a Skype. Email me here to arrange...
Living on a classic suburban lot (100' x 70') I'm faced with the typical shortage of room to build antennas for the lower bands. While I was able to tune the 100-foot dipole on 80 meters well enough for 80 meter WAS, performance on 160 meters was sub-par. It's easy to see why since I was operating with a dipole only 25 feet above the ground - a fraction of a wavelength on 160 - which meant that most of my signal was going up, not out.
After exploring my 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, and turn it into a vertical by twisting the leads together and feeding them into one side of a balun. The real work would then involve laying out radials, needed to act as a counterpoise. The small footprint of my property required a creative layout of the radials:
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, with lines drawn showing the four original ground-based radials placed along the fence
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?
An SWR under 1.5:1 on all 8 bands between 80 and 10 meters was possible with an MFJ-941E tuner. But even with the tuner getting a decent on most of 160 meters was impossible, as evidenced by this plot of SWR vs. f:
Plot of 160 meters adjusting the MFJ tuner for best SWR every 25 kHz (frequencies above band limit of 2 MHz displayed to show the dip.)
Getting a 25' vertical to tune up on the lower end of 160 was going to require a loading coil. Using EZNEC Woody modeled the antenna and calculated parameters for a base-loaded coil that would not only electrically extend the antenna but also eliminate the need for the balun.
I got a short piece of PVC, and cut two holes, one
for a binding post with banana jack (to which I could
attach radials) and another hole for an SO-239.
The coil is connected to the center of the SO-239
on the inside of the tube and the wire threads to the
outside where it is wrapped 38 times around a 2" piece
of PVC, then threaded back inside...
...so it could exit 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
The new coil, installed, with black tape wrapped
around the 10ag wire.
Here is my first reading at the base of the antenna with an MFJ-259B - thanks to Erik (KE1V) for the loan
So let's look at the plots of SWR, Resistance (R),
and Reactance (X).
Even though R was above 50 ohms across the band, I could still operate in the lower end of 160 without the use of the tuner (look at that SWR!) and through the spring static got some good reports on 160 (thank you 1900 Net.) Operation on 80, 40, and other HF bands was also possible with the MFJ-941E tuner.
Nurse... elevate me
Now it was time to tackle R, with its unacceptably
high readings. 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 in N6LF
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 the fence, as seen below....
The red lines show where the first two elevated radials being tested are attached to the fence
This annotated aerial shows the path of 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.
Here are the plots of SWR, R, and X with the original 4 radials (shown in red) and after the addition of the 2 elevated radials (shown in blue). Note the rise in SWR, but the improvement in Reactance and major improvement in Resistance:
Some other interesting things happen with the
addition of the 2 elevated radials, like a steeper bend in
the plot of X, which indicates an increase in Q. But
most important to our goal of improving system output is
the lowering of R across the entire band, with 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 improved
(lowered) R, in fact 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 to the 160 meter ground system
The results, plotted in
green below, show that SWR rose and X did
not change appreciably from the levels measured with 4 (red) or 6 (blue) radials. The
plot for R shows that the extra 2 radials (8 radials) reduce R across
the entire 160 meter band by about 5 ohms and into the 30
ohm range near the lower part of the band, which is
precisely in the targeted area of the band.
By the fall of 2011 I felt like I got to the point
of diminishing returns with the radials and decided to
operate that winter with the system as is, and see how I
did. Which wasn't bad - in fact, it was pretty damn
good, with 41 states and 9 countries contacted, a HUGE
improvement over the dipole.
May 2012 Update
Really enjoyed the 160 vertical, but missed my 80/40/30 dipole, so I took Woody's suggestion and added a relay so I can switch the antenna back and forth between a dipole and a vertical, remotely from the shack.
A circuit diagram of the remote antenna switch
The base of the antenna just after closing up the relay box, showing more of the twin lead above the relay box, which will act either as the vertical on 160 or a feed for the dipole on 80.
In the shack, this MO-DPDT switch is wired to send 12v to the relay at the base of the antenna with opposite polarities, depending on the selection of 80 or 160. The polarity for 80 selects the twin lead (turning the vertical into an 80 meter dipole) while the polarity for 160 selects the base coil (so, with the two leads shorted turns the antenna into a vertical.)
The relay, showing the effects of water (humidity?) inside its plastic case.
Just like Roy Scheider in Jaws, I was gonna need a bigger boat. Or, in this case, a bigger relay, one with contacts wider apart (to prevent arcing even in humid weather) as well as a box that would protect it better from the elements. (When I opened the first box up, there was a small pool of rusty water at the bottom - not sure if that was all humidity or some leakage from rain)
Annotated look at the feeds to the new relay. I eliminated the banana jacks, instead threading both the 80 meter feed and 12v supply directly, through holes in the box that were heavily caulked.
Now, I don't get on the air much in warm weather, and 2015 was a pretty harsh winter, with something like 110 inches of snow in just a few weeks, so when the nice weather arrived I wasn't going to spend much time in the basement. Now it was November of 2015 - and getting cold (shivers of dread) - so I thought it would be a good idea, before the snows arrived, to sweep up each band to ensure I could get on all the HF bands.
Yikes! Immediately I saw serious problems on just about every band, save 10 meters; inability to tune-up, can tune up (using the IC-718 ultra-low power feature) but full power saw the SWR spike above 5:1 and, on 12 and 15 meters, having the tuner's indicator lamp glow like a supernova when I keyed up. Hoping it was something simple I started the troubleshooting by disconnecting and reconnecting all the coax and twin-lead. Nope, that didn't do it. I opened up the case in which the switch is located, and gently sanded the relay connectors. No dice.
The result of three and a half years of New England weather on the relay
Close-up of just a few of the connections that were redone after the discovery of serious oxidation. Those two solder joints to the jack up top were so loose it is amazing that the antenna worked at all in either 160 Vertical or dipole configuration.
The fun never stops. Just a few months after fixing the above, the problem returned but now it was on 160 meters, with the vertical. This time, I discovered another weak link in the antenna system: the banana jack I had cleverly installed in the PVC to easily connect and disconnect
Also saw a return of SWR spikes (See above, the Janauary 2016 Update,) but only when using the dipole on 40 and 80 (no such problem on my 40 meter dipole, narrowing once again the problem to the antenna switch,) so I went back and re-soldered and re-screwed connections inside the box, eventually getting the problem to disappear. The question, of course, is for how long...
September 2017 Update
Someone PLEASE make the fun stop ;( As I explain on my QTH page, in 2017 I discovered that the tree in which I had hung one side of the 100' dipole had been girdled (that's when varmints nibble away the bark, preventing the tree from getting water and nutrients, effectively killing it) so I had to have the tree removed, and then installed this 40' aluminum mast from ChannelMaster, which holds up the north side of the dipole/top cap for the 160 vertical.
After two snowstorms and a deep-freeze (temps below zero for a few days) we caught a break mid-January with a few glorious days in the 60s! I used one of those days to go back out to the base of the antenna and pretty much do what I did in January of 2016, which was to clean up all the connections (inside: sand the relay contacts and screws for the twin-lead, outside: sand the exposed twin lead that connects to the top of the box because they, too, had developed a coating that was preventing a good connection to the relay.) All is well, once again. This fall I will make it a point to get ahead of this.
The weather people are saying "March is the new February," and I can attest to the fury of the March 8th storm. Because it started as rain and THEN turned to snow, it weighted down everything outside, including the 40' ChannelMaster mast which, when I woke up the next morning was bent beyond help. ***sign*** guess I'm restricted to 20 meters and above until I can decide on a replacement, likely a 50' Rohn which, because I can have the tube sections intersected with each other (especially up top) could be strong enough to withstand another onslaught. (Notice I said "could" and not "should")
My new, very kind neighbors next door gave me permission to hang one side of my dipole/vertical from their tree which is just over the fence on their property. After a few flings of a one ounce fishing weight with my sling shot (purchased a ham flew market) I was quickly back in business. Here's an annotated aerial of the property with the new alignment of the dipole/top cap (blue is a 20 meter dipole and green is my ten meter dipole):
As luck with have it, the center of the dipole ended up directly over the outdoor switch box, which elimiated the need for me to move it and all the support cabling and power line. Back on the air with both long dipole and 160 vertical, and picked up a few more long-distance countries (Iceland and the Slovak Republic) on 160...
Took advantage of what for passes in a New England winter for a pleasant day and took out my sling shot, a 5oz weight and some fishing line and pulled. Hard. Got the antenna raised 16' higher. As you can see below, the vertical AND higher dipole are performing beyond my wildest hopes...
Two views of the antenna (l: back of the house, r: from the front) now 16' higher...
Countries Contacted on 160
Holy crap! New Zealand and Antarctica on 160!
(This exchange almost doubled my previous distance record on 160)
I also have all the Lower 48 states and over 65 countries. Yes, I count the Orkney Islands separately from Scotland (go to www.joeandnemo.com to learn why). Countries marked in red were collected after the extending of the vertical in January 2019.
|Trinidad & Tobago||9Y4/VE3EY||FK90ik||CW||2308|
Kitts & Nevis Island
|US Virgin Is.||NP2J||FK77ps||CW||1762|
|Turks & Caicos Is.||VP5CW||FL41aa||CW||1495|