An Outbacker Perth on the rear rail is sounding better all the time!
Art
Ralph E. Ahseln wrote:
*----- Original Message ----- *
*From: "Phil Agur" <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>*>*
*Subject: RE: catalina27-talk: backstay antenna*
**
*> My concern on a C27 install would be just what kind of antenna
length is
> left when isolate down from the top and isolate 8 ft off the cockpit
floor.
>
> I'll swag the isolated antenna wire would be about 26ft. Icom calls it a
> long wire antenna but how long is long, and I leave it Ralph to us
what that
> means.
>
> Phil Agur s/v Wing Tip
> *
**
**
*Phil , et al,*
**
*Without getting too technical.. It's all about Wave Length.. And
that's the problem.*
*The commonly thought of most "efficient" antenna is One Half Wave
length of the frequency (WL/2)*
*WL(meters) = Speed of Light (radiation propagation= 300,000,000
m /sec ).. Divided by the Frequency (Hz ) *
*Or...*
*WL(Meters) = 300 / F (Mhz)*
**
*The International Distress Frequency is ... 2.182 Mhz or about
137 meters = .*
*Half Wave 137 / 2 = ~ 69 meters = ~ 230 feet !!! *
*That would be a very long BackStay Indeed..*
**
*And the "top" of the HF (SSB) Is roughly 10 meters *
*Half Wave = 10 / 2 = 5 meters or... about 15 feet !!*
*Certainly workable on most boats.. *
**
*BUT.....*
**
*How is it possible to have SSB transmission throughout those Wave
Lengths ? *
*A "magic black box " called an "Antenna Tuner " *
*It's job is to make the wire "LOOK" like it's different lengths..
Electrically.. But as in all things.. A compromise means less
efficient.. *
**
*In the truest sense a .. Long Wire Antenna should be MULTIPLES of a
FULL Wave .. So in the strictest definition *
*a Long wire antenna for the Distress Frequency of 2182 Khz should
be at least 460 feet long !!! or longer !!*
**
*However , Many of us probably would call a Half Wave single length of
wire a "long wire" as well but that still ..Either has to be around
230 feet or IF shorter..... Have an antenna tuner..*
**
*The Radiation pattern of any radiator is affected by .. It's
operating frequency, It's length .. AND.. what "Parasitic" elements
(such as shrouds, stays) are nearby,... THEIR lengths ....and their
distance from the Radiator...*
**
*It's all about radiation .. *
**
*Whew... My brain hurts .. LOL*
**
*Questions ??*
**
*Ralph Ahseln*
**
*P.S.....I sure hope my math was all OK.. At my age the brain gets
fuddled on numbers sometimes LOL*
**
