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Author Topic:   Revenge-22 WT ground wire
ratherwhalering posted 08-19-2006 10:52 AM ET (US)   Profile for ratherwhalering   Send Email to ratherwhalering  
'Mornin whalers,

I just removed a interphase loran/depth finder from a 1989 Revenge-22 WT (and installed a Garmin 498) and there is an odd ground wire in the helm area that runs to a grounding plate on the transom.

Is this original, and if so, where does she go?

jimh posted 08-19-2006 02:00 PM ET (US)     Profile for jimh  Send Email to jimh     
LORAN radio receivers listen for radio signals at very low frequency, 100-kHz, and it was common that instructions suggested connecting the chassis of the receiver to a grounding plate in contact with the water or to the vessel's bonding system. This was done to enhance the effectiveness of their radio antennas. The connection to the water or to the vessel's bonding system provided a counterpoise for the very short and inefficient vertical monopole antenna used to receive the LORAN signals.

As an aside, in the LORAN system all the stations transmitted on the same frequency, 100-kHz, and their signals were very carefully and precisely interwoven by a pulse modulation technique. Stations were synchronized together into chains, and, by comparison of the delay between the arrival of these signals, hyperbolic lines of position could be deduced. With three or more stations being received, a position fix could be deduced. There were usually four stations in a chain. To make the synchronization more complex, some stations were linked into more than one chain.

The technical details of LORAN are quite interesting. It is apparent that a few engineers stayed up late and drank a lot of coffee working out the details of how this would operate. The low frequency of operation permitted long ground wave reception and minimized diurnal variations in propagation. For a terrestial-based system, it worked quite well, and was used as early as the 1940's.

towboater posted 08-22-2006 08:17 PM ET (US)     Profile for towboater  Send Email to towboater     

If the chassis ground loop is connected to submerged zincs, does that qualify as a ground plate in contact with the water?

Is it possible fresh zincs could improve modern GPS, radio and depth sounder performance?

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