Some years ago I had to shelter for a few days away inside a sea lough on the west side of the Isle of Jura, where there was no habitation for many miles and no VHF reception
. I regretted not having maintained even a simple HF receiver like that mentioned below. I have since made amends, and quoting from my post #1258 just 3 years ago: "My antenna
setup was described in a previous post, with a little modification - I now use R58 coax clipped to the backstay with the screen
clipped to the rudder
stock as an earth. The other end is coiled around a ferrite bar salvaged from a vintage radio
direction finder, then to an old atu module from a military surplus HF manpack, then to the rtl-sdr.com dongle and from there to a Dell notebook. The dongle is controlled by SDRSharp, and piped to OpenCPN
using Virtual Audio Cable (VAC). I'm afraid have no knowledge of Linux
, and have yet to succeed in in getting the rtlsdr plugin
to control the dongle.
This setup allows me to get very clear images
from Offenbach which is over 1,000 klms away.
In the past I have had success with a Sony 7600, and later a Degen DE1103 with a little tuned loop antenna. The Degen SSB
tone control (these SW sets have a circuit called a Beat Frequency Ossilator - BFO to put a tone on each SSB) is much more sensitive than the earlier Sony model, and it can also recharge it's own batteries"
The dongle mentioned is the version 3 which does not need any upconverter for HF and has excellent frequency stability on an accuracy of -1 PPM. Configure the SDRSharp Sampling Mode to Direct sampling (Q branch).
When VAC is installed select Line 1 in the Audio/Output box on SDRSharp and the Preferences box in OpenCPN Weatherfax plugin picks that up when Audio is selected there. The best frequency for me to get wefax from Offenbach DDK is 7,878.5 khz USB with 3,000 BW. If using a laptop/notebook you sometimes get "stepping" on the picture, which comes from interrupt routines in the operating system and is mostly resolved by switching off any battery
saving routines and ensuring the the battery
is fully charged. This "stepping" can make the image unusable for the morphing procedures in the plugin.
My best frequency for Northwood wefax is 4,608.5, but Offenbach is much better. I also managed to get a poor image once from Boston on 9,108.5 when on the SW coast of Ireland
I also use Multiplex which does not need SDRSharp to decode SYNOP/SHIP transmissions, also from Offenbach, on 7,644.507 khz.
As you can see these frequencies are 1.5 khz down from the published frequency to allow for the sideband.
I can also tune & decode Navtex by using SDRSharp with Fldigi, and of course any HF voice transmissions can be heard just on SDRSharp.
All of the aero and marine
frequencies can be tuned by switching to a different antenna, as well as broadcast stations
A neighbouring boater who is an electrical engineer
and a HAM showed me a modern ATU about the size of a matchbox with a small loop antenna which he uses, but I have not seen his wefaxes. I'm sure the large ferrite rods and ferrite inductors in my old ATU filter an awful lot of noise
RTL-SDR.com has an article about a hacked GPS
antenna to tune satellite
which I have yet to be successful with.