Howard wrote:
On 5 Jul 2004 18:41:38 -0700, (ken) wrote:
Finch wrote in message ...
I'm planning a long road trip in a couple of weeks. I planned on
driving primarily at night and I thought it would be interesting
to be able to listen to shortwave along the way.
So my idea is to take along my DX-390, sit it in my lap and twiddle the
knobs as I drive. I'll listen through an earpiece.
snip.............................................. ...................
You will get much better reception if you put a mag-mount antenna on
the roof of the car and run the attached co-ax lead to the DX-390.
Get an adapter for the co-ax plug from Radio Shack. The easiest place
to find a mag-mount antenna is at a truck stop. They usually have
CB-type
mag mounts for $25.00 or so. You have to modify the coil so make sure
you
get an antenna where the coil is a good size where you can get at the
windings.
The CB coil is resonant at ~27 mhz and has to be modified for the SW
bands.
The easist way is to bypass the coil with a jumper wire across the
coil.
This is usually enough to give you an untuned whip which will work
fine on SW.
If you find one of the CB antennas with large coils you can replace
the CB coil
with a hand-wound coil of smaller wire and many turns. This will make
the
antenna broadly resonant in some part of the SW spectrum. If you
really want to boost performance you can put taps on various parts of
the coil but that may
be more than you have time to tackle right now.
Another quicker, better way is to get a BIG mag mount and a 10 mhz
whip
from a ham radio supplier, but that would cost more. Also, the antenna
acts as a
thief magnet and has to be stored in the trunk each time you park.
Another useful item for mobiling with a portable is a small FM
transmitter
designed for automobiles. You plug in an audio source switch it on,
and you can
hear your radio, casette, etc on you car radio with lots of volume.
Wal-Mart
has them for about $20. I found that on my setup, the SW7600G was a
bit short
on volume.
Modern car radios are buried so deep in the dashboard that it is
usually
quite a project to get at the Motorola plug at the end of the car
antenna lead, but that is another possibility. You would have to get a
3-foot extension and the correct adapter, but the car antenna works
fine and you wouldn't have the use of
the car radio.
To sum up
1. The cheapest way is to use your existing car antenna if you can
get at it. Adding a length of whip didn't seem to
help much.
If you do add a length get the 56" fine whips used
on amateur
2-meter antennas to keep the wind loading down
2. The next way is to get the CB mag-mount and modify it.
3. The best way is to get an amateur mobile antenna. Make sure the
total height does not get you whacking street power
and phone
lines or low bridges.
After trying all the above, I found the modified CB antenna the
best. It didn't stick up too high, used a smaller magnet, and was easy
to remove to the trunk, and with taps, was just about as good as the
ham antenna.
Considering the vast wasteland that is AM broadcasting, SW is
worth the trouble.
Sorry about the fragmented text: it looks perfect when typed: must
be some setting buried in Netscape.
Generally good advice. The question I have is regarding the mods to
the CB antenna - did it really make much of a difference with the coil
bypassed?
I have used my Icom R2 to listen to shortwave while mobile. Granted,
it's not a great performer on the sw bands (bandwidth is a bit wide)
however with a 19" magmount (2 meter 1/4 wave antenna) I've been able
to hear the major broadcasters. Does the '390 have memories? If so
it would be to your advantage to pre-program your favorites and just
hit a button or two versus fiddling with the tuning knob.
Have a fun trip,
Howard
It's easier/better to buy a magnet mounted whip antenna with no coil
than removing the coil from a CB antenna. Radio Shack has magnet whips
with no coil. The longer the better for shortwave use.
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