Certainly for contemporary military and Coast Guard ships, the vertical is
the solution for all the stated reasons in this discussion. However, until
very recently commercial shipping used long wires for routine communications
and special verticals for vlf, and until 1980, mf direction finding. With
requirements to have quiet times 2-3 times an hour to monitor 500 kHz plus
the need to do ship's business on 4, 8, and 12 mHz (among other freq), an
end fed long wire was the simplest solution for most owners.
The comments about the RF environment on military ships is very interesting
because that was one of the reasons that the Aegis class cruisers were
developed. They are generally assigned to a carrier battle group with the
carrier responsible for attack communications and the Aegis cruiser
responsible for defensive communications and the two ships linked on a high
speed data channel. In addition, if the Comm center on either ship is
damaged the other could assume that role. So you have complementary roles
and redundancy.
My son was on the CG-49 USS Vincennes in the 1980's and he setup and managed
a MARS station aboard ship and he told me that they could only operate
during a time and place when the ship could shut down certain comm links
because of RFI to and from the MARS station.
David, K1LD
----- Original Message -----
From: <blueis@sprintmail.com>
To: <Towertalk@contesting.com>
Sent: Thursday, March 14, 2002 8:24 AM
Subject: Re: [Towertalk] Antennas over Salt Water.
> Ted K6HI stated...
>
> > All the navy and coast guard ships I have ever seen, and been on many,
all
> > have vertical antennas for HF. They usually have two, on opposite
sides,
> > one on starboard and one on port.
> >
> > I have never seen a beam on one for HF. Doesn't this say something?
>
> Sure does... the environmental conditions make a yagi/LPA a BAD choice:
> wind-driven rain entering traps
> high winds (hurricane takes out antenna)
> lack of space ( a Hy-Gain 3-30Mhz log periodic WOULD
> look good!)
> changes in ship's heading would require constant
antenna
> positional changes
> and these are the first ones that a 'ground-pounder' could
> think of!
>
> I think it says that a vertical is the best survivable choice -- given all
> possible conditions.
>
> gary b
> RVN BTO
>
>
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
|