[Milsurplus] AN-104

[jcoward5452 at aol.com]

Well,I didn't read Jack's input until after my last post, but I think 
the sheath is isolated from the radiating element.The sheath is also 
structural support for whatever "long wire" was installed.You don't 
want the "long wire" to be an electrical element for the VHF antenna.
 Are there no manuals applicable to these antennas specifically?
  I love a mystery but this stuff should be well documented I would 
think.
 Jay KE6PPF

-----Original Message-----
From: jcoward5452 at aol.com
To: cosmoline at aa4rm.ba-watch.org; scr287 at sbcglobal.net
Cc: milsurplus at mailman.qth.net
Sent: Wed, 10 Jan 2007 8:32 PM
Subject: Re: [Milsurplus] AN-104

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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