----- Original Message -----
From: "Phil Agur" <[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
>
> 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
