[TowerTalk] Re: Radials over salt water
Thu, 11 Jan 2001 18:36:12 -0500
Have to add my two cents here based on five years of ocean/bay-front
In preparing for Field Day when I first moved here to Casey Key Island,
Florida, I conducted some antenna tests running QRP which was our planned
mode. These were simple, but practical SWR/Bridge measurements and
on-the-air antenna comparisons. My QTH is ocean front with the high tide
line about 350' from the back of the house and the Bay side about 300' from
the front. I'm on the South end of the island and the island runs NNW from
me. The take-offs to Europe are over the Bay and the path to JA/Oceania is
over the Gulf.
Tests were made from my dock on the Bay side with the rigs in my boat.
Antennas were a 1) A4S at 50'; 2) a bob-tail at 50' with half of it
suspended over the bay ; 3) a Super Loop at about 36' (tilted to a low
point about 20' from the ground and at the edge of the bay); and 4) a
Cushcraft R-7 mounted at the end of the dock on a dock piling and up about
30' on a pushup mast. The common ground was an 8' copper rod driven into
the bay under the dock in about 4' of water. It was also connected to a
large piece of fencing which was maybe 10-12' long and laying on the bottom.
Take-off to the N and points East were all over the Bay.
Results: All the antennas performed far above expectations. On 40 and 80
the loop was used primarily because it worked better for US Q's, but the
Bob-Tail was a killer for EU DX. The R-7 also performed very well on all
bands. The loop was the quietest antenna and as a result was very effective
on 80 and 40. For DX, the Bobtail was usually 1 S Unit better than the R-7
or in the case of QRP, making a Q or not being heard. For DX, the R-7 was
consistently better than the Loop on 40 but the noise levels on 40 with the
R-7 usually had us back on the loop for hearing. The Bob-tail was directed
North and was generally said to be louder than the R-7 by most NE USA but
who said they couldn't tell the difference until we started A/B tests with
EU. There the Bob-Tail was always better, but again not by much. We ran 5W
or less and in some tests kept reducing the power until we were unreadable
on one antenna or the other.
During FD, we worked a lot of stations who couldn't believe we were QRP
because we were S7 to S9 on the high bands with the A4S. The A4S was always
better than the R-7 as expected, but all our operators were really surprised
that we usually got thru on the first or second call running only 5W on the
R-7. On 80, it was a big surprise to work guys we could hardly hear. Of
course FD antennas aren't always the best. The R-7 is of course a 3/8 wl
vertical with a counterpoise and needs no "ground" but it does seem to work
quite well over saltwater. All the antennas seem to work better over
I have also conducted A/B testing with two other stations that are a few
miles inland. On 40M, I can consistently hear and work DX that they don't
hear at all with comparable rig/antenna setups. This seems to be especially
true for Far Asian/Indian Ocean DX. Often when operating mobile, I can be
working JA's on the island who simply disappear after I cross the bridge
over to the mainland. The same is true when driving onto the island.
Stations seem to pop out of the noise as I near the bay.
Not scientific, but I've operated over 40 years now from all over the world
with all kinds of antennas. I just always remember the best conditions seem
to have been in the Caribbean or on the Islands and beaches here in Florida.
I call the Ocean, nature's Amp! Works for me.
Jon Hamlet, W4ZW
Casey Key Island, FL
"A little bit of Paradise in the Gulf of Mexico"
One of the W1AW/4 Crew - IARU/WRTC-2000
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