You don't mention how high you will be above sea level. Too high and
the "L" gain & angle won't improve as much as within 1/2 WL and a few
meters above sea level. So the 160L is ok at 80m from the tide line but
the 80m ought to be closer if you can manage that. More than a
wavelength from salt water and a vertical is pretty much a normal over
dirt vertical.
I'm a believer in elevated radials for expeditions. Two resonant ones
work within a fraction of a db of 4 or more elevated. Only one and its
less than 1.5db such as the steppIR crankIR. It still takes a lot of "on
the ground" radials to minimize the ground losses, even close to salt
water (perhaps unless there is salt water intrusion just below ground
level).
Rudy Severns has done a lot of research and modeling.
antennasbyn6lf.com. Relative to more compact elevated radials, check his
article "Short Radials for Ground-Plane Antennas" in the ARRL antenna
Compendium vol 6. A single inductor and two elevated radials as short
as 1/8 wl are within a fraction of a db from 1/4 wl. My plan for my
next DXpedition.
I've used DHDL's which have RDF much better than BOG's, which really
don't work over salt water infused soil/sand/coral. It's easy to make
DHDL's switchable 180 deg, which might be useful EU vs US. If you are on
granite then the usual 200' BOG length advice seems ok, but I've not
tried them. But most any Rx only antenna will help, especially if you
have diversity synchronous radios (e.g. K3 with 2 receivers for CW or
SSB integration in your head). Sometimes the noise rejection worked on
bands not expected (eg 15m Rx on an 80m DHDL). Experienced but not modeled.
No experience with VP2E's.
Good luck, have fun and I hope to work you!
Grant KZ1W
On 6/29/2019 4:21 PM, Martin wrote:
Topbanders,
Operators from VO and DL teamed up to go to Ile aux Marins, a small
abandoned island just a few 100 meters from St.Pierre , FP . We are
right now planning our antennas.
There is daily tourism on the island , so the antenna farm can not be
big. The location is about 80m from the sea, so we hope for good take
off angles.
For RX, we plan to use BOGs. How long should we make them? Do you think
this may work?
For TX on 160m and 80m we plan to install inV L's with radials on the
ground. What number do you suggest minimum near salt water?
40m vertical , 30m vertical: Will we be better off with VP2E's or with
verticals and radial field? What do you think? Any hint welcome.
Other bands: Hexbeam.
Please visit www.fp2019.net
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