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O
N THE BENCH
PROJECTS, REVIEWS, TIPS & TECHNIQUES
A Camping DXpedition -
Part 2
Photos and Story by David Payne Sr.
If you look at radio project magazines from
the 1920s, you’ll see that people took their
radios everywhere. For any outdoors activity
you could possible imagine, people figured
out a way to take these early radios with them.
Among the most memorable to me was a project
for installing a crystal radio on a bicycle – one
wonders how it could be ridden with that bulky,
homemade radio on the handlebars – and another
for enjoying radio in a small sailboat. The
sailboat mast served as means to erect a vertical
antenna, while a ground wire trailed underwater
behind the boat.
There’s no reason we can’t do that today.
In fact, it’s far easier for us. We have radios
capable of amplifying sound, so you don’t need
to drag along a bulky set of high-impedance
headphones. Our radios are also capable of amplifying
signal, negating the need for stringing
up a great deal of wire – although you surely
can if you want to.
You don’t necessarily have to go on an
overnight trek to enjoy your radio out-of-doors,
nor do you have to use a cumbersome antenna
to enjoy the experience. Even a simple trip to
a park with a portable radio can get you away
from RFI and offer a vastly improved listening
experience.
When I was a young man, I worked for a
city park which was located atop a very high
hill. I traveled from park shelter to park shelter
throughout the day, stopping at each for an hour
or two to pick up trash, clean the restrooms and
hose off the concrete surfaces. And, I listened
to shortwave while I worked.
My setup was very basic – and it had to
be because I couldn’t be erecting and taking
down nice, big antennas several times a days
on the city clock. I had a Radio Shack DX-360
portable. It was the perfect radio for the task,
only 10-inches long with 9-band coverage. For
an antenna, I had a piece of small-gauge wire
about 20 feet long with an insulator and rope on
one end and an alligator clip on the other.
I simply set the radio on a picnic table,
attached the alligator clip to the antenna,
and tied the other antenna end to one of
the support posts at whichever shelter I
happened to be working.
Even though it was in the middle
of the day – as well as the middle of
the summer – I enjoyed great reception.
Radio Netherlands, in fact, sounded as
strong as a local AM station and it was
while working there that I heard my name
on radio for the first time – a letter read
on-air by Radio Netherlands.
❖ Choosing your
antenna
In most camping experiences,
you’ll be liberated from the antenna
constraints of home. Unless there is some special
rule prohibiting it, you can temporarily install basically
any antenna design you want. If you bring
plenty of rope, insulators, wire, and a couple of
copper rods, you can erect any antenna imaginable.
Last month, I discussed a fan longwire I had
built for camping. There are, however, many other
options.
The camping antenna that is most exciting to
me is the Beverage antenna. A typical Beverage
is a single wire one or two wavelengths long. A
resistor connected to a ground rod terminates the
end of the antenna pointed at the target area.
This is a very simplified version of it, but
the Beverage works like this: on a typical endfed
longwire, signals coming from behind the
feedpoint first travel all the way down to the other
end of the antenna. Once it reaches the other end,
it’s reflected back. The beverage is directional,
because most of the signal coming from the rear
is sent to ground instead of being reflected back.
In the AM band, a one-wavelength Beverage
could be more than 1,000 feet, but for a shortwave
band, such as 31 meters, your one-wavelength
antenna would be around 100 feet.
To construct this antenna, you’ll need one
end terminated at an insulator – with a feed line
for your radio coming off of it – and the other end
terminated with a clamp that you can attach to a
ground rod. Between the end of the antenna and
the ground clamp, solder in a 470-ohm resistor –
you could try using different resistor values to see
what works for your soil.
When you add the resistor, your soldering
joint may not be able to hold the weight of antenna,
so you’ll need to relieve some of that stress.
One way is to make a small loop of wire at the
resistor’s location and hold it together with a zip
This diagram shows how to couple your outdoor antenna
to your portable radio.
tie so that when the antenna’s own weight pulls
upon it, the resistor is safely tucked away in the
loop. As long as the loop doesn’t slip, there will
be little tension force on your resistor’s solder
joints.
Before you go, attach the clamp to the ground
rod and check to make sure there is conductivity
between the antenna and ground rod. If nothing
else works, one temporary – and easy – grounding
solution I’ve found is simply wrapping a long
section of bare wire around the copper rod and
holding it securely with a common hose clamp.
One benefit of this antenna is that it’s not
something you’ll need to hoist into the trees. In
fact, it should be only a few feet above the ground
to work properly. However, it can be a very serious
trip hazard if installed too low, so it would be
more suited for installing in remote areas. Even
so, I would try to keep it at least 8 feet from the
ground at its lowest points. Even if you know it’s
there, it can be very easy to stumble into during
darkness.
Make sure it’s pointed where you need it!
The Beverage is a highly-directional antenna, but
because of its length – and you will surely have
to work it around obstacles in a forested area – it
will be cumbersome to adjust. So make sure it’s
pointed in the right location. Use a compass to get
your bearings, which you should obtain from an
azimuthal map centered on your location.
If your location doesn’t have room for a long
antenna, you can still get plenty of wire in the air
by going horizontal and vertical with a delta or
quad loop configuration. Since your radio will be
receive-only, you have a great deal more freedom
in how your antenna is configured.
It would be nice to have an impedancematching
transformer and 50-ohm coax line to
couple your radio to this antenna, but that’s
not always an option with portable radios.
If you have external antenna and ground
jacks, you can still use coax – and have one
end of your loop going to the coax shielding
and the other to the center conductor.
This should still work nicely even if you
don’t have a variable capacitor or two to
tune your loop.
If your radio doesn’t have those jacks,
you can still connect it by wrapping insulated
feed wire around the telescopic
antenna of your radio and terminating that
feed wire to a second ground.
68 MONITORING TIMES August 2012