Re: catalina27-talk: RF Ground

[Doug Simonsen]

Larry,   RF ground is not usually much of a problem unless you have HF radio gear on board for operating in the amateur or marine SSB bands.  In those services, a good RF ground is needed for proper operation of the antenna.   For the VHF radios and depth-sounding gear that most of us carry, the RF ground is not nearly as critical.  If you try a few different ground points, you'll probably find one that works just fine with the fishfinder.    Here's a link to a Raymarine tech support FAQ item that discusses this issue:   http://raymarine.custhelp.com/cgi-bin/raymarine.cfg/php/enduser/std_adp.php?p_faqid=382&p_created=999647004&p_sid=yX5qWX6i&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9NDMmcF9wcm9kcz0wJnBfY2F0cz0wJnBfcHY9JnBfY3Y9JnBfc2VhcmNoX3R5cGU9YW5zd2Vycy5zZWFyY2hfbmwmcF9wYWdlPTEmcF9zZWFyY2hfdGV4dD1yZiBncm91bmQ*&p_li=&p_topview=1   Doug Simonsen Kiwi, #1522 Anacortes, WA ----- Original Message ----- From: Larry Robertie To: catalina27-talk@memberclicks.com Sent: Sunday, May 07, 2006 4:03 PM Subject: RE: catalina27-talk: RF Ground Thanks Ralph,   The ground is actually an entirely separate wire,  No cover, just twisted wire.    I did a bit of research on the net.  Seems as though this earth ground can be bought in the form of a $250 copper plate bolted to the outside of the boat.  Not gonna happen.  I also saw quite a few folks advising that the ground can be made by connecting to either the exterior metal (shrouds), the engine, or drilling into the lead of the keel.   This all leads me to believe I may just install the thing, try various grounds, like the green wire, and see if I get any interference on the other electronics.   Larry       From: catalina27-talk@memberclicks.com [mailto:[EMAIL PROTECTED] On Behalf Of Ralph E. Ahseln Sent: Sunday, May 07, 2006 6:48 PM To: catalina27-talk@memberclicks.com Subject: Re: catalina27-talk: RF Ground   Larry,   This question is a lot more complicated than it looks on the surface. But the Simple (?) answer is.. Connect it to the SHORTEST lead to "Earth Ground" as possible. Less than 10 feet if possible.   So how do you make an Earth Ground on a boat ? Not easy. Again, the Simplest (?) answer is to connect it to the largest metal object that's NOT insulated from the Water.   What the idea is , to make sure the Pulses of the Fish Finder (Possibly rich in RF) do not radiate into your Stereo, TV, VHF or Marine HF radios you may have on board.   Can you tell if the lead is part of a SHIELD around the Positive and Negative leads ? Probably so. And that is the coupling to Earth of spurious RF.   It's all about RF induction, Impedances,, and all that kind of Smoke and mirror stuff ..  :-) And boy you want to start a Flame war..   Just get a bunch of Hams and would be engineers started on this one.. LOL   once or twice I tried to get folks to clarify terms.. To no avail. RF Ground, Earth, Common, Ground Plane, Negative, and Return (ugh, never use that one)  Are all different cats.   UW Ralph Ahseln Oblio Gresham OR