[Milsurplus] Car Whip Antenna "gain"

[Facility 406]

On 8/14/2025 04:29, Jeff Kruth via Milsurplus wrote:
> 24 dB? Over a standard antenna?

102", with a loading coil, resonant at, say, 1.5 MHz, compared to 39" of 
wire, resonant, at, maybe nothing at all in the AMBC band.

> Hmmmm. But aperture gain? There is no aperture.

Aperture seemed to be a better description of a wire in space gathering 
energy, like a lens, with much more physical size, like what one can see 
with a pocket monocular, compared to a telescope with a 60" lens at the 
front.  Not aperture gain, a larger aperture, a larger energy gathering 
area.  "A bunch more wire chucked into space to pick up more things" 
doesn't sound quite right.

"In fact, a car antenna is not considered an antenna at all, except in 
name. At a frequency of 1 MHz, wavelength is 300 meters, so a 1 m long 
whip is .3 %. The proper name and way to consider it is as an
"electrostatic field probe"."

Try asking for an electrostatic field probe when a tree branch snaps 
one, and you go to the dealer, of local Napa Auto Parts, or anyone, 
anywhere, at any point in time, of the past 100+ years...  "Aerial" 
might work 100 years ago, or in the UK.  I'm thinking they consider it 
an "antenna".  Probably everyone does.

"You can scarcely make it "resonant" with a coil, sorry."

Well, shoot, WTH are series loading coils in antennas for, I mean, 
beyond the whole inductive/capacitive/reactance thing, and, well, 
"resonate", and hopefully work better in a field, I guess...?  I dunno, 
just tossing words out there.

> However lengthening the probe will make it intercept more 
> field, So sure, longer is better.

Like, a bigger energy gathering aperture?  Perhaps not the best, or even 
the most common term, but I picked it up a few years ago from a fellow 
in defense that was focusing photonic energy at what we call RF through 
metallic RF "lenses", the same as he was using other equipment to focus 
the same type of energy, at what we call light.  Only the size of the 
equipment, and some material changed, to match the frequencies, and 
wavelength in use.

Maybe the shape of his was different, and hence, more aperture-like in 
appearance, as we consider it in optics?  Maybe he was using the term as 
in geometry, and lines meeting at a point.  Is the word no longer used 
like that?  Hard to say, but it made sense for the application.

> Still 24 dB is a gain of 250 X. Still hard to believe, as not directional.

A resonant 102" whip, with loading coil, resonant at operating 
frequency, compared to a random wire about 39" long?  Relatively 
speaking, perhaps.  It may still suck, but it may be +24dB over even 
suckier (highly technical jargon).

If one squishes the somewhat beach ball shaped lobe of an antenna, of, 
say, 360 degrees elevation (is it still elevation when going downward?), 
down into a narrow disk at the horizon, where the ground-level broadcast 
transmitters are, even though it's still 360 degrees when looking from 
the top, is there no relative gain if that lobe is now only 10 degrees 
"high", picking up 100% of a roughly 10 degrees span of intended signal, 
and 350 degrees less of nothing wanted at all?  Is that not directional? 
  Does directional not work like that?

> The "coax" for the standard car radio set-up was just a low capacitance shieIded wire, to try to get the 
> maximum voltage into the radio

Pretty wild shielded wire design.  Center conductor surrounded by a 
dielectric, then shielding, then an outer jacket, with shielded 
connectors at each end, of a coaxial design.  At what point does it 
switch from shielded wire, to coaxial cable?

Had some oddball stuff in my old sedan, 93 Ohms, and peculiar press-on 
connectors.  Researched it, found the stuff was called "coaxial cable", 
made by Ford Aerospace, originally designed for satellites in the 
1970's, which may explain why it was found in a Ford.

Although, I have seen stuff like you mention once, a single solid wire, 
flopping around in what looked like 1/4" ID ice maker tubing, with a 
shield, and connectors.  Still coaxial in appearance and design, but 
terrible stuff to work with.  I wonder what the capacitance was of the 
wire flopping from side to side, varying by a few mm, and if it was 
stable?  The constant buzzing in the cabin drew my attention to it, as 
the center conductor rattled around.  Thinking back, I saw it used 
twice, both by Toyota, in the 80's, and 90's.  Those Japanese are always 
forward thinking in their designs!

> Just so you know that this is not opinion pulled from some nether orifice, I am an antenna guy by 
> profession, who also taught college, with experience in EMC testing, antenna pattern measurement, field strength > measurement, etc. Just so you know I am not in the class of the modern "no-nothings".

I'll dig up the article, as I'm re-reading the book I found the 
information in.  I don't know what B&W claimed, but I recall a specific 
AMBC coil was mentioned, and the group that had done the testing, was 
called the "3995 Mobileers", which was created right after WWII, and 
focused on mobile antenna development from the mid-40's, into at least 
the 80's, as the book was written in 1988.

Anyway, 102" of antenna electrostatic field probe with loading coil, 
resonant at operating frequency (is it an antenna yet?), sounds better 
than 39" of "antenna", with no coil, resonant at nothing in the same 
range, so I figured I'd take the idea of the dozens of guys, playing 
with the ideas for decades, that measured the relative gain, run with 
it, and see if there is a plug-and-play consumer-level improvement for a 
guy with a thing on a fender, driving around with a radio, picking up 
some stuff.

I'll keep plugging away, I'll figure out this whole antenna notion yet!

Kurt

P.S., Your name sounds familiar, but I may be confusing it with a 
fellow, last name "Carruth" that I went to school with, but, I came 
across this, so not the same fellow:

https://www.arrl.org/hamfests/microwave-update-2013-conference