Return-Path: Received: (qmail 93800 invoked from network); 15 Jan 2004 03:09:05 -0000 Received: from unknown (HELO ptb-mxscan02.plus.net) (212.159.14.236) by ptb-mailstore02.plus.net with SMTP; 15 Jan 2004 03:09:05 -0000 Received: (qmail 38264 invoked from network); 15 Jan 2004 03:09:05 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore02.plus.net (212.159.14.216) by ptb-mxscan02.plus.net with SMTP; 15 Jan 2004 03:09:04 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1AgxsV-0009qC-Vu for dave@picks.force9.co.uk; Thu, 15 Jan 2004 03:09:04 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Agxrt-0001P3-4f for rs_out@blacksheep.org; Thu, 15 Jan 2004 03:08:25 +0000 Received: from [213.46.243.28] (helo=amsfep15-int.chello.nl) by post.thorcom.com with esmtp (Exim 4.14) id 1Agxrn-0001Jo-IV for rsgb_lf_group@blacksheep.org; Thu, 15 Jan 2004 03:08:19 +0000 X-Fake-Domain: Peter Received: from Peter ([24.132.154.248]) by amsfep15-int.chello.nl (InterMail vM.6.00.05.02 201-2115-109-103-20031105) with SMTP id <20040115030749.FSDT3882.amsfep15-int.chello.nl@Peter> for ; Thu, 15 Jan 2004 04:07:49 +0100 X-Bad-Message-ID: no DNS (Peter) Message-ID: <029e01c3db14$7e78ca20$f89a8418@Peter> From: "Peter van Daalen" To: rsgb_lf_group@blacksheep.org References: <014d01c3dac6$cd3aabe0$f89a8418@Peter> <4005E8D7.7000301@mindspring.com> Date: Thu, 15 Jan 2004 04:05:56 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: LF and /MM performance offshore. Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 2 Content-transfer-encoding: 8bit

Thanks, Frank, this is definitely most interesting info for me.

Could anyone make now a rough estimation of the possible total /MM performance gain in dB over a well equipped and favourably situated land station ?

I mean the possible " real " seagain effect as per Franks speculation plus the effect of the " virtual " seagain thru much better antenna efficiency because of the vessels' steel hull and deck etc. in salt water plus the effect of flat and undisturbed 360 degrees radiation surface ( sea ) plus the effect of reduced or near zero manmade noise at high sea ( I have 26.4 KWH DC battery banks onboard for the EME in statu nascendi and during Rx/Tx I switch AC generators off ).

All electrical/electronic gear ( except the mandatory navigation gear, but these are very well shielded ) is switched off during Rx.

73, Peter, PE1ECM

----- Original Message -----

From: "Frank Gentges" <fgentges@mindspring.com>

To: <rsgb_lf_group@blacksheep.org>

Sent: Thursday, January 15, 2004 2:11 AM

Subject: Re: LF: Re: lf andnoise and offshore.

> Peter,
>
> AMRAD conducted several winter trips to the Outer Banks of North
> Carolina to listen to LF signals in the days before transatlantic
> amateur signals were common. The Outer Banks are a long narrow strip of
> land several miles offshore from the North Carolina mainland. We
> observed LF broadcast signals and compared to what we were seeing at
> sites more inland were stronger. We attributed this signal difference
> to sea gain and would put its value at 10 or more dB in the few cases we
> observed although we did not make careful measurements.
>
> The ITU has put together a model for radio propagation and includes a
> factor for sea gain. It only works out to be worth a couple of dB in
> the test cases we ran. I think the ITU model does not recognize the
> amount of sea gain that is available from moving to the sea coast for
> the really best conditions at least below 200 kHz.. I am convinced it
> is there and is significant.
>
> Also the noise was low but we could find quiet sites inland and we just
> could not hear the Transatlantic signals nearly as well inland.
>
> <caution, speculation on> I speculate that the LF waves are combining.
> and adding in phase due to the long wavelength, at the sea water
> interface and traveling in as surface waves stronger than the low angle
> sky waves that created them.. Similar to glints or mirages we see
> optically. <speculation off> We can hear other surface waves at 770
> kHz on the Outer Banks from New York City duirng the day and night. We
> cannot hear them much past a mile inland as the land kills the surface
> wave propagation. While we did not conduct a similar experimant on LF I
> suspect they would also fade down to the sky wave strength if we went
> inland.
>
> Frank K0BRA