to Original Article on MonitoringTimes.com
By Bob Grove W8JHD
When you’re operating VHF/UHF portable, it’s really no big
deal to find an adequate antenna. Resonant elements are short,
and a gain antenna doesn’t require vast expanses of real estate.
But for the HF ham operator or shortwave listener, a resonant
element can easily be 60-100 or more feet in length, and a
multiband antenna can impose a daunting challenge. Often,
a transmatch (“tuner”) is employed to cancel the reactance
of an impedance-mismatched antenna system.
And what about restricted apartments, camping locations, business
trips, or even Field Day? And how about long-distance emergency
comms after a natural disaster or other unforeseen event?
Wouldn’t it be nice to have a compact HF antenna that folds
up to a few inches to fit in a pouch?
The military has done it in the past with interchangeable
elements, inductively-wound elements, or even reeled metal
tape measures which can be unfurled to an appropriate length
for the band chosen. Perhaps it’s the latter approach that
may have inspired this interesting product from DWM.
Multiband Antenna to Go
The dipoles are assembled around pairs of enclosed, fishing-style
reels which resemble a “Yo-Yo,” as first observed by Jeffrey
Lauterbach, the son of DWM’s owner, Bill Lauterbach (WA8MEA).
Each reel can release up to 40 feet of insulated, stranded,
#22 wire; a pair can effect a dipole for 40-meter operation
(7 MHz), or shorter for higher-frequency bands up through
two meters (148 MHz).
The basic “Deluxe” pair YYTD-259 includes a pigtail PL-259
male connector for transceivers; the YYTD-PHN is equipped
with a 1/8” (3.5 mm) phone plug for popular multiband portables
like most Radio Shack, Sony, Grundig and Sangean radios; and
the YYTD-RCA provides an RCA phono plug for models like the
Sangean ATS-803 and Radio Shack DX-394, DX-440 and some older
receivers and transceivers. All “Deluxe” models are $29.95
each plus $7.95 shipping.
For multiband operation, the new, four-reel, dual-band, model
Yo-Yo-Vee model 4 ($49.95 plus $7.95 shipping) or six-reel,
tri-band, model 6 ($59.95 plus $9.95 shipping) may be in order.
The multiband pairs of reels are connected to a popular Budwig
center insulator affixed with a standard SO-239 female “UHF”
connector for transmission-line attachment.
If you have a transmatch handy, you can trim the VSWR very
low, even on lower frequencies than 7 MHz. Or simply use the
transmatch with the basic YYTD-259.
The Budwig insulator also has a center hole to support the
dipole and relieve the strain on the deployed wire.
Erecting the antenna
The reels are encapsulated, not open, to resist moisture intrusion
and prevent unraveling. Each reel has a handy, molded loop
to facilitate tying it to a support (tree limb, building eave,
pole hook, etc.). When erecting both ends of the dipole, you
will need to provide lengths of tether cord; these can be
used to tie down securing stakes for the poles as well.
A tie-off tab is provided on each reel for wrapping a turn
of wire to keep it from unraveling further once the proper
resonant length is established. The reel is equipped with
a spinner knob which assists in both deploying and spooling
The six reels which comprise the tri-band dipole are colored
by pairs, assisting the operator to equalize lengths on each
side of the center insulator. Actually, this isn’t really
necessary since all three pairs are electrically connected
to the same point on the center insulator, but it’s a thoughtful
While the small-gauge wire may appear skimpy, it is sufficient
for both receiving and transmitting (100 watts or so).
If you don’t have trees or eaves to support the dipole, you
will need to provide masts. DWM suggests telescoping lengths
of rigid PVC; it’s strong, cheap and lightweight. Try to get
it up as high as possible, since a horizontal dipole will
react reflectively with the ground, distorting the radiation
pattern to favor overhead instead of the desired horizon.
It’s best to feed the antenna with lightweight RG-58/U coax;
larger-diameter, heavier RG-8/U will provide no significant
improvement except when in very long runs (well in excess
of 100 feet) at HF.
And one final tip: You may wish to measure off correct lengths
for the band(s) of operation, wrapping a small piece of contrasting-color
tape at those points, or brushing on a swath of paint. This
makes it much easier to deploy the right length of wire in
For more information including ordering, contact DWM Communications,
P.O. Box 87, Hanover, MI 49241; or phone them at (517) 563-2613
(orders) or (517) 563-9022 (business). Email: firstname.lastname@example.org
or visit their website: http://qth.com/dwm.
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