[Milsurplus] AN-104

[jcoward5452 at aol.com]

The radiating element in these antennas is just a piece of stripped 
coax stuffed in a wooden mast.The metal sheath is there for "armor" 
only.It is not connected to the antenna circuit in any way except loose 
capacitive coupling.It may have a reactive contribution to the 
radiation characteristics of the antenna/airplane combination and these 
characteristics have been studied and plotted laboriously by techies of 
a previous era.Remember the fundamentals:antennas are special cases for 
transmission lines.

-----Original Message-----
From: cosmoline at aa4rm.ba-watch.org
To: scr287 at sbcglobal.net
Cc: milsurplus at mailman.qth.net
Sent: Wed, 10 Jan 2007 7:41 PM
Subject: Re: [Milsurplus] AN-104

Jack u wrote:

> I was looking for another manual tonight
> and came across AF manual 52-19, "Antenna Systems"
> |
> |
> It goes on to
> say the radiation resistance is approximately 50 ohms
> so no matching section is necessary, and for a resonance
> at 128 mc, the antenna can be used from 100 to 156 mc.
>
> Now it would be interesting to know if this is a
> simplified description, or an accurate representation
> of the insides of the AN-104.
>
> Jack Antonio WA7DIA

Perhaps 100 & 156 are 2:1 swr points. Maybe 70 ohms @ 156 & 30 @ 100. 
Thats
center freq. +/- 20%

It's old wisdom that to broadband a dipole you increase element 
diameter.
So if AN104 some 6" around that sheathed wood core, you'd have an 
effective
L/D ratio of 10% (L=19", D=1.9"). At 3.75 mhz that'd be about L=70' & D=
1.8" to give a 2:1 swr band from 3 to 4.2 mhz.

I wonder

Now isn't the antenna is a streamline tear-drop cross-section? So
D=6" would deform to a 1.9" diameter circle

Many have seen station fotos where the wire dipole elements have 
spreaders
that form
an abstract cage. Reason: broadbanding. In fact I think there's such a
drawing in
an ARRL antenna book.

I don't have the math & hygeine to support such. I'm clearly writing 
from
a corner marked "Empirical."

A ARC-5 VHF manual is here & will snoop

Tnx W7DIA

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