RE: catalina27-talk: backstay antenna

Tue, 10 Jan 2006 22:48:40 -0800

If I remember correctly the ground plane was by hocus pocus (capacitive coupling for Ralph) from a large sheet of copper foil on the inside of the hull below the waterline to the water surface. Cabo to San Diego over 750 nautical miles was clear as a bell on the IC-M750RT.

 

Obviously the automatic antenna tuner (needs to be automatic as the required tuning changes with frequency) so the transmitter is loaded correctly but I’m not sure of the signal strength impact of dropping from 40 ft of antenna on a bigger cruiser to 26 ft on antenna on a C27. Maybe a good question for Icom Tech Support.

 

Phil Agur                    s/v Wing Tip

Commodore,             Call Sign WCW3485

IC27/270A                   MMSI 366901790

www.catalina27.org      Vessel Doc# 1039809

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ralph E. Ahseln
Sent: Tuesday, January 10, 2006 8:14 PM
To: [email protected]
Subject: Re: catalina27-talk: backstay antenna

 

I should make one important Addendum.

 

A QUARTER WAVE antenna will ACT like a HALF WAVE.... IF.....

 

IF....  There is a PLANE in apparent Opposisition to the Radiator..

 

That is.. 

 

IF...  you have a GROUND PLANE that is equal or larger than the Quarter length.

Radiation will "See" that as a continuation of the HALF WAVE..

 

So it is likely that in Marine installations...  A ground PLANE  ( NOTE A "Plane")

Is made to act as part of the system..

 

Often the Backstay and a Ground Plane is the Antenna on a vessel..

 

So the Radiator can be ONE QUARTER WAVE LENGTH..

 

How one accomplishes that GROUND PLANE.. is a subject that makes for a lot of anger and Heated discussion..

 

It's a lot more complicated than just ..  Tying to the Backstay and the BONDING strap of a boat..

 

At least .. In My Humble Opinion...

 

ralph

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