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Mobile DXing can be fun
By Mike DiPersio, KC2Q
I'm not sure if there is an award for DXCC/M (mobile), if there is,
I'm not aware of it. If there is not, then there should be. At any rate
I have been HF mobiling for about 25 years now and enjoying it very much.
I have had many different size HF rigs in the mobile from Yaesu FT101's
to Kenwood TS130 to Icom IC730 to the IC735, this last one for about 10
years - now I'm with something even smaller yet, the Icom IC706 MKIIG.
As a single unit it's small enough to locate on or near the dash area
when I owned a Toyota Camry, since replaced with a Dodge Caravan. But
when you take the removable head and just place that somewhere on the
dash, (velcro works good) the body of the radio can be placed under a
seat somewhere or in the trunk, it becomes a stealth radio, practically
invisible.
The antenna can be from a number of different sources. After trying
many, I chose Hustler, a 40 or 20 or 10-meter resonator on a 54 inch mast
works really good, but having to stop to change resonators every time
I wish to change bands does get to be a bore (I band hop a lot!). So I
tried their multiband adapter. It worked fair, but not great.
That's when I designed my own adapter about 20 years ago. It is in a
90-degree format with one resonator forward into the wind and the other
two swept back for lower wind resistance, all horizontal, and one resonator
holding this assembly in place, allowing four, not three, bands plus the
54 inch mast which gives me 6 Meters. The horizontal resonators act as
a ground plane to the vertical, and the vertical resonator and the mast
do much the same for the other bands, plus I now have the benefit of any
of five bands to go to with just the touch of the band switch on the rig.
No stopping, no changing resonators, etc. Eventually I made it out of
stainless steel rather than aluminum - keeping the coefficient of metals
similar.
I find that the quadband or multiband antenna adapter as I call it,
gives me a 58% increase in reception as well as transmit when the assembly
is together instead of working the resonators individually as a monoband.
I prune each resonator individually before I put them into the assembly.
Then I fine tune each resonator, starting with the highest frequency in
use working my way down to the 40-meter or 75-meter resonator. An SWR
of 1:1.5 can be achieved on 10, 12, 15, 17 and 20 Meters almost across
all the amateur portions of each of these bands. 40 Meters normally gives
me approximately 20 kc above and below the resonant frequency when used
as a mono. However, when in the assembly it becomes a little wider, 3040
kc above and below the resonant frequency (usually 7.255). I have done
very little with 75 Meters, therefore I can't comment on that band. Iÿ
have been making these adapters for close friends and club members over
the years. I have however, been told by others that 75 or 80 Meters works
similar to the 40meter resonator but with a higher "Q" - only
1020 kc above and below the resonant frequency.
It's true, it can be somewhat of a package, (four resonators plus SS
Adaptor) but with a 40 or 50 lb. test monofilament fishing line to prevent
the antenna from leaning back, it works ok. I can be traveling on the
Florida Turnpike at 70+ mph with no problems.
Once I reach my destination, and would like to operate from the base,
I simply remove the mast, which is on a quick disconnect, and place it
on a ball mount already mounted on a 10-inch diameter by 5-inch high cake
tin. I have wires in the length for 10, 20 and 40-meter dipole style,
connected to the cake tin to act as a ground, taking the place of the
vehicle.
This base assembly works very similar to the way it does on the car.
If it's on a roof of the building somewhere or in the field, use some
more fishing line as guys to keep it from blowing over. In my case I put
the antenna on the balcony of the condo rental in Key West, FL supported
by a "bungee" chord with a plastic wastebasket as a spacer from
the metal railing.
The IC706 MKIIG sits very comfortable atop a switching power supply (very
light in weight) 12 volts 20 amps. I also fieldtested a 12volt power booster;
it's like a car battery but somewhat lighter, with a handle and rechargeable.
Worked great. Good for jump starting other cars as well.
In the three weeks of my trip I worked a schedule on 14.305 daily from
1300Z to 1500Z and again from 2000Z to 2200Z with many Hams who join in
on the 305 group from areas in NJ, NC, AZ, TN,NY and many other states
like IL, NV, OH, TX, NE as well as stations from other parts of the world
- YJlPD,VK3JBH, NH6IG, 5B4/ RW3GW, HR6/AH6PN, EA3EVR, SP9LJD, and P43E.
All of these contacts, as well as many more from outside this threeweek
period of driving to and from Florida, have been worked with only the
100 watts the IC706 has to offer. Most of the signal reports were 59 and
59 + both to me and from me, from the mobile or the portable setup on
the balcony.
I have enjoyed this trip and you could also. Mobile HF or just DXing
is really a lot of fun. However, the logging can become a little difficult,
but with a small tape recorder to log the calls, times, frequencies, names
etc. or a copilot to log for you, can make it pretty safe.
Good luck and happy mobiling.
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