Car radio whip antenna question
Twitchell
around them. The wraps are not close but lazily spiral down the length of the
antenna.
Does this help reception? Is the coil attached somehow to the car or just the
antenna itself?
twitch
bpnjensen
My antenna on my minivan is like that.
I think the supporting whip is fiberglas/or some insulating material,
and the wire is the actual electrical element; and in the interest of
saving length and providing strength, they wrap the wire around the
slightly shorter antenna pole. The wire is then connected to the lead
of the antenna. It works fine, about as good as a metal whip of
similar length. Antennas for cars are pretty uncomplicated
critters... :-)
user
It adds inductance.
I think the Fanfare antenna has such a special spool that ? makes it better
?.
--
--
What's on Shortwave guide: choose an hour, go!
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bpnjensen
> It adds inductance.
Really? That's a pretty loose coil on those things, how much
inductance can it have? And frankly, do the auto manufacturers
actually *think* about things like this when car radio technology is
already so implicitly satisfactory?
We are talking about the same thing, right? Just a loose wrap of wire
on the nonconducting whip core vs. an actual compact coil?
Bruce
******
> I think the Fanfare antenna has such a special spool that ? makes it better
> ?.
>
> --
> --
> What's on Shortwave guide: choose an hour, go!http://shortwave.tk
> 700+ Radio Stations on SWhttp://swstations.tk
> 300+ languages on SWhttp://radiolanguages.tk- Hide quoted text -
>
> - Show quoted text -
Twitchell
bpnjensen says...
>
>On Jun 10, 12:55=A0pm, Twitchell <Twitchell_mem...@newsguy.com> wrote:
>> I've seen some car radio whip antennas that look like they have a wire wr=
>apped
>> around them. =A0The wraps are not close but lazily spiral down the length=
> of the
>> antenna.
>>
>> Does this help reception? =A0Is the coil attached somehow to the car or j=
>ust the
>> antenna itself?
>>
>> twitch
>
>My antenna on my minivan is like that.
>
>I think the supporting whip is fiberglas/or some insulating material,
>and the wire is the actual electrical element; and in the interest of
>saving length and providing strength, they wrap the wire around the
>slightly shorter antenna pole. The wire is then connected to the lead
>of the antenna. It works fine, about as good as a metal whip of
>similar length. Antennas for cars are pretty uncomplicated
>critters... :-)
I was wondering if I could improve my portable radio FM reception by wrapping it
like the car antenna by just wrapping it with a wire.
bpnjensen
> In article <49b45573-b11c-45d1-9ec7-c9f17cfe8...@n37g2000prc.googlegroups.com>,
>
> - Show quoted text -
Where do you use your radio? If it's inside a building with a heavy
metallic or masonry contruction, that may be the problem.
To your question - my guess is not. FM wavelengths are fairly short -
about 1 meter in length - and your antenna is probably a pretty good
length already if it is a half-meter or so (roughly 20 inches or a bit
more). Wrapping a wire around it would not affect its resonant
wavelength, and attaching a wire to it may or may not help, but too
long an antenna is not terribly helpful as a rule either.
A better choice might be to either take the radio to a place where
there is interfering metallic or masonry building in the way, or make
an external antenna for it.
Gregg
Hmm, I've never seen that. I have seen the radio whips that have wire
around them but they are then encased in plastic, like some CB
antennas are.
Gregg
I can't believe I have never seen that before. Wouldn't there be a
chance for eventually the wire to work itself free, is it glued or
clipped to the whip?
Gregg
> In article <49b45573-b11c-45d1-9ec7-c9f17cfe8...@n37g2000prc.googlegroups.com>,
>
> - Show quoted text -
If you really want to improve your car's FM performance that bad you
have two alternatives IMO. Number one, simply replace your antenna
with an antenna just for AM or number two - go up to your local
Autozone or whatever you have in your area and buy one and add it on
yourself. There really is nothing to it unless you may have a physical
disability like a bad back or something like that. Add on a switcher
and your good to go. All cars should be done that way from the factory
IMO.
bpnjensen
>
> - Show quoted text -
Picture a thin pole (the whip) with a very gently coiled wrap of wire,
a turn every inch or so, from top to bottom. Then, the entire thing
is covered with a wrap of something like shrink-wrap to hold it
altogether. Unless the antenna is traumatized, the wire is pretty
much set for life.
Gregg
>
> - Show quoted text -
Yeah OK, you didn't mention that is was encased, I thought it was
flowing freely in the wind, my post above mentioned what you just
said. ;-)
Twitchell
Gregg says...
>
>On Jun 10, 3:55=A0pm, Twitchell <Twitchell_mem...@newsguy.com> wrote:
>> I've seen some car radio whip antennas that look like they have a wire wr=
>apped
> of the
>> antenna.
>>
>> Does this help reception? =A0Is the coil attached somehow to the car or j=
>ust the
>> antenna itself?
>>
>> twitch
>
>Hmm, I've never seen that. I have seen the radio whips that have wire
>around them but they are then encased in plastic, like some CB
>antennas are.
That's what I'm talking about...they're encased (sometimes) in plastic.
D. Peter Maus
Chrysler started doing this a number of years ago on their fixed
length car antennae. Ford and GM do it, now also.
It appears as though there's a wire, under the black polymer
coating, wound around the metal post end to end. If you look very
closely, however, you see that the 'wire' ends just before the small
ball at the top and just before the hex fitting at the bottom. It
appears to be nothing more than a superficial contrivance.
In fact, it's there to break up the airflow around the antenna at
speed. Fixed length antenna made of the usual single piece steel rod
tends, under some conditions at speed to vibrate wildly both
loosening in it's fitting, and making unnecessary noises in the cab.
They also have an unfortunate tendency to whistle.
Chrysler started with a simple sheath with different aerodynamic
properties, made of plastic, slipped over the rod to eliminate these
properties. They made quite an issue of them in TV and billboard ads
in the 90's.
Ford suppliers, on the other hand, made the rod with this same
spiral twist on it's stainless steel antennae. Expensive, but
retaining the brightwork appearance of their traditional fixed
length antennae. And if you can find one, you'll see that the spiral
is actually manufactured into the surface of the rod, with a sharp
cut on one side of the spiral and a gentle slope blending into the
rod on the other. But this was expensive, and Ford, too, have gone
with the black polymer coating with what appears to be a wire embedded.
Since these antennae are all provided by an handful of suppliers,
all the car manufacturers using and fender mounted fixed length
antenna have gone with the black polymer coated spring steel rod,
with what appears to be a wire embedded.
This is for aerodynamics. Not for any electrical property.
amdx
"bpnjensen" <bpnj...@yahoo.com> wrote in message
news:49b45573-b11c-45d1...@n37g2000prc.googlegroups.com...
Car antennas my be simple critters, but the coax used is special.
Mike
Twitchell
Thanks. Your explanation makes sense and I guess there's no reason to
incorporate this into the whip antenna for a portable radio.
thanks again
twitch
Krypsis
(100MHz)is 9.8357 feet. A quarter of that is 2.458925 feet. Therefore,
a quarter wave whip needs to only be about 30 inches long to be resonant
in the FM band, a not unreasonable length for portable applications. I
seem to recall that most aerials on portable radios are approximately
that length when extended. You would only gain then if you desired to
have a shorter aerial than 30 inches yet still retain optimum reception
ability. I might add that, short of a lot of trial and error, you would
need to delve into aerial theory in order to even retain the reception
performance you currently experience.
Krypsis
Krypsis
most often on 27 Mhz CB radios. They often had a base loading coil at
the lower end. This would look like a solid piece of cylindrical pipe at
the base of the antenna.
The spiral of wire is the "active" element of the antenna. The whip
itself is usually made of fibreglass much akin to that which a fishing
rod is made from and has a support function. The assembly allows a
degree of flexibility without damage to the whip, the coil of wire, or
the mounting point, a feature necessary in mobile applications.
By spiralling the active element, you simulate the desired length of the
active element. In the 11 meter CB band, a quarter wave is about 9 feet.
Therefore, a 9 foot quarter wave aerial would be resonant in the 11
meter band thus having the best transmission and reception ability. A 9
foot aerial isn't practical in most automotive applications as they are
easily damaged or may damage other objects. The compromise then is to
helical wind the element. In most 11 meter applications, the helical
winding isn't sufficient so some extra matching is required. On some
helical whips, this takes the form of the windings being wound more
finely near the tip of the aerial (top loading). In other applications,
the resonance is achieved by a "loading coil" attached to the base of
the whip (bottom loading). It is said that top loading provides the best
results but I always preferred base loading coils for my applications.
I came across the last relic of my CB era the other day when I was
cleaning out my garage. It is an old magnetic base whip. It wasn't one
of the helical wound whips. Instead, it had a base loading coil and the
whip itself was about 5 feet of spring steel. It proved very useful in
the 70s when I was involved in desert rallying. Just attach it to any
vehicle, no drilling or mounting brackets required, and it used the
entire vehicle roof area as a "ground plane". Being magnetic, it was
somewhat less useful on some of the early Toyota Landcruisers with the
fibreglass rooves.
So, in summary, yes, it really does help reception as it provides a
better impedance match between vehicle and radio.
Krypsis
Radiomatt
> The FM band is 88 - 108 MHz.
Hold on, young fella. That depends where in the world you are. Japan
uses 76–90 MHz, and the OIRT band in Eastern Europe is 65.8–74 MHz. It's
only the rest of the world that uses 88-108 MHz!
dave
No electrical purpose whatsoever. It keeps the whip from whistling in
the wind.
dave
>
> Hmm, I've never seen that. I have seen the radio whips that have wire
> around them but they are then encased in plastic, like some CB
> antennas are.
On a Firestick, the wire is real.
dave
87.9 - 107.9
Krypsis
OK, then use the calculator on this website to readjust your figures if
you live or intend to live in those regions.
http://www.1728.com/freqwave.htm
88 - 108 is the most common. You will also note that my example of
100MHz is not exactly the centre of that spectrum but, for the purposes
of the exercise, close enough.
Krypsis
Krypsis
What's a few KiloHertz between friends, eh?
Krypsis
bpnjensen
Thanks for this Peter. I always thought that concept as an RF
resonator was suspect! :-D
D. Peter Maus
It's not a bad thought. There are a number of antennae that are
made with a helical coil around a form. RF System's MTA is made this
way.
But we're talking many more turns, around a broader form, and a
tighter gathering of turns along the length to be practical as an
antenna.
bpnjensen
>
> - Show quoted text -
Indeed, something where the coil would become an actual inductor and
serve to provide additional electrical length where physical length is
restricted. Along with HF broadband antennas, mobile CB and ham
loaded antennas are typical examples of what you are talking about, I
assume - can't see much reason for this with an FM antenna, the lambda
being so short.
Gregg
I know that.
RHF
> On Jun 10, 12:55 pm, Twitchell <Twitchell_mem...@newsguy.com> wrote:
>
> > I've seen some car radio whip antennas that look like they have a wire wrapped
> > around them. The wraps are not close but lazily spiral down the length of the
> > antenna.
>
> > Does this help reception? Is the coil attached somehow to the car or just the
> > antenna itself?
>
> > twitch
>
>
> I think the supporting whip is fiberglas/or some insulating material,
> and the wire is the actual electrical element; and in the interest of
> saving length and providing strength, they wrap the wire around the
> slightly shorter antenna pole. The wire is then connected to the lead
> of the antenna. It works fine, about as good as a metal whip of
> similar length. Antennas for cars are pretty uncomplicated
> critters... :-)
Auto makers went from Telescoping Whip Antennas
to Solid One-Piece Stainless Steel Antennas because
of lower Cost and greater Durability.
The Fiberglass Rod with Wrapped Wire Whip Antennas
were done for the same reason : lower Cost and greater
Durability; over the life of the Car/Truck.
idtars ~ RHF
.
RHF
>
> > - Show quoted text -
Most likely the Wire Wrap is done as a function
of improving the Mechanical 'properties' of the Whip
and not for any Electrical 'properties' associated
with the performance of the Antenna.
~ RHF
.
RHF
> In article <49b45573-b11c-45d1-9ec7-c9f17cfe8...@n37g2000prc.googlegroups.com>,
The Core of the new Auto Whip Antennas is
Fiberglass {non-metal} and thus the Wrapped
Antenna Wire is a Free Element in Space.
Wrapping a Wire around your Metal Whip Antenna
effectively couples the Wire to the Whip and makes
it part of the Whip Antenna Element.
-if- the Wire Wrap only extends the length of the
Whip basically you gain nothing.
however -if- the Wire Wrap extends the length
of the Whip and the un-wrapped Wire then extends
beyond the Whip you have effectively Extended
the Whip Antenna.
idtars ~ RHF
.
DEFCON 88
about window antennas. My Mitsubishi Galant has an antenna embedded in
the rear window. It's not one of those dipoles that you used to (or
still?) see embedded in the front windshield of GM cars. Rather, it
has a peculiar folded design that's hard to describe. It works very
well. I get exceptional reception, especially on AM. In fact, one of
the reasons I chose the Galant is because it had the best AM reception
of all the cars I test drove. What's the theory on these window
antennas? Do they have a pre-amp ahead of the radio?
dave
Mine are crossed active loops at MF frequencies. Folded dipole at FM freqs.
Ian Jackson
<8bbf2e76-cb7c-4404...@z25g2000vbk.googlegroups.com>,
Gregg <gk...@earthlink.net> writes
I once made a helically compressed 80m halfwave dipole by winding each
leg of around 66' of PVC insulated wire on 33' of the type plastic line
used for rotary clothlines/airers (making sure, of course, that the
inner core was nylon, and not steel).
I marked the line every 6", and the wire every 1'. After a few false
starts, I soon got the knack of getting the spacing of the turns
correct. I suppose that diameter of the line was around 1/8", and I
needed to space the turns at around 3/8".
Obviously, I had dipole consisting of 132' of wire, but I have no idea
whether the turns were close enough to make a significant increase in
the inductance per unit length, thereby loading the antenna, and making
it electrically longer than a halfwave.
I only used the antenna once, at a scout 'Jamboree on the Air' event. I
put it up as an inverted V, with the centre at about 30', and the ends
at 20'. I used 300 ohm feeder. It was very sharply tuned (using a
balanced Z-match tuner). Daytime conditions on 80m were not very good,
but the antenna seemed particularly poor. I think I only managed a
couple of contacts, with only S5 reports where I would have expected
s9+.
40m was a bit better but, at the end of the day, just before we packed
up, things seemed distinctly lively on 20m. I got a 59 from 350 miles
away and, surprisingly, another from 40 miles (extremely short skip
conditions, it appeared, which may have explained the poor conditions on
80m).
I haven't bothered to try the antenna again. I have no idea if it was
working OK on 80m, and the poor performance was simply poor conditions.
I've still got it somewhere, so maybe one day, I'll get around to it.
--
Ian
Brenda Ann
"dave" <da...@dave.dave> wrote in message
news:4c13e4da$0$5494$bd46...@news.dslextreme.com...
The old window antennas weren't dipoles at all. Both "elements" were
connected to the center of the lead-in. The only reason for the dipole
appearance was symmetry, which helped to make them less of a distraction to
the driver.
RHF
wrote:
> "dave" <d...@dave.dave> wrote in message
The embedded Wire Windshield Antennas used
two very thin parallel wires and the two created
a larger signal capture area plus the two provided
some redundancy if one should break.
The newer Printed-On Window Wire Antennas
{Circuit Trace (Wire) on Glass}
have a great sectional width {less likely to break}
and go around and/or across the Window.
At least that is how the one we have in the rear
side window of the Ford Windstar Van is laid-out
it come in {starts} from a single contact point and
goes almost all the way around the rear-side
Window with a 1/2" gap between the far-ends;
plus there is an extra leg starting in one corner
of the Window that goes across the Window at
a Diagonal Angle; and yet another extra leg
starting at the opposite corner of the Window that
goes across the Window at a Horizontal Angle.
* Sort of a bent & folded Window Windom Antenni
FWIW the Ford Windstar Van's Rear-Side Window
Antenna seams to work very well down in the SF
Bay Area but poorly up here in the mountains :
While the Solid Metal Whips and the Wire Wrapped
Whip Antennas seam to do as well in the SFBA
and much better up here in the Sierras. This may
be due to the fact that the Whips actually project
out away from the Body {counterpoise} of the Car
and are physically by-design a better EMF "Probe"
then the Foil-on-a-Window Antennas.
and that's how i hear it on the radio ~ RHF
.
dave
SLJ21...@aol.com
>
> - Show quoted text -
I spent 33 years at General Motors Product Service Engineering and I
can tell you that on General Motors vehicles the wire wrapping on the
antenna is there to break up the air stream around the mast so it
doesn't whistle in the wind stream.
Krypsis
The theory is they are simple and vandal proof! They also lessen the
effect of an external aerial on the aesthetics and the aerodynamics of
the car. No wind whistles on these window aerials!
Krypsis
bpnjensen
I don't think the windshield-internal dipoles work as well on FM as a
good external vertical whip of the proper dimension. They are not
omnidirectional, nor are they vertically polarized, both of which are
helpful for FM in a moving car. The folded ones may have different
characteristics that overcome these drawbacks, I don't know for sure.
Moreover, they are not likely the AM antennas at all - almost every
car AM radio since dirt has used a ferrite- or air-core coil antenna;
far more effective than a whip or wire ever could be. Especially the
ferrite, it gets you what a whip cannot - ~ full wave resonance and
high relative gain. Match that with a quality AM radio and you'll
have a nice MW DX machine in your car. I love listening to stations
on the Great Plains when driving overnight to Yellowstone :-)
Bruce Jensen
Brenda Ann
"bpnjensen" <bpnj...@yahoo.com> wrote in message
news:00f9d188-c9d7-427e...@k25g2000prh.googlegroups.com...
I don't think the windshield-internal dipoles work as well on FM as a
good external vertical whip of the proper dimension. They are not
omnidirectional, nor are they vertically polarized, both of which are
helpful for FM in a moving car. The folded ones may have different
characteristics that overcome these drawbacks, I don't know for sure.
Moreover, they are not likely the AM antennas at all - almost every
car AM radio since dirt has used a ferrite- or air-core coil antenna;
far more effective than a whip or wire ever could be. Especially the
ferrite, it gets you what a whip cannot - ~ full wave resonance and
high relative gain. Match that with a quality AM radio and you'll
have a nice MW DX machine in your car. I love listening to stations
on the Great Plains when driving overnight to Yellowstone :-)
Bruce Jensen
1) Those were not dipoles. The use of two wires was for symmetry purposes
only. They were not directional at all.
2) The only AM car radios that ever used a loop or loopstick antenna were
the "pull-out" portables. Almost every car radio ever made (up until
digital readout synthesized units) used variable inductors for tuning, but
for tuning only, because they were more stable than variable capacitors.
The antenna was and has always been that whip on the fender/cowl/windshield.
These are far more effective than a loop or loopstick in an automobile,
since those type antennas do not work at all well inside a steel structure.
I guarantee you that if you unplug that whip from your car radio, it will go
silent (unless you are sitting next to the transmitter site.)
RHF
> On Jun 13, 7:22 am, Krypsis <kryp...@optusnet.com.au> wrote:
>
>
>
> > On 13/06/2010 4:30 AM, DEFCON 88 wrote:
>
> > > OK, this deviates somewhat from the topic, but I've always wondered
> > > about window antennas. My Mitsubishi Galant has an antenna embedded in
> > > the rear window. It's not one of those dipoles that you used to (or
> > > still?) see embedded in the front windshield of GM cars. Rather, it
> > > has a peculiar folded design that's hard to describe. It works very
> > > well. I get exceptional reception, especially on AM. In fact, one of
> > > the reasons I chose the Galant is because it had the best AM reception
> > > of all the cars I test drove. What's the theory on these window
> > > antennas? Do they have a pre-amp ahead of the radio?
>
> > The theory is they are simple and vandal proof! They also lessen the
> > effect of an external aerial on the aesthetics and the aerodynamics of
> > the car. No wind whistles on these window aerials!
>
> > Krypsis
>
> I don't think the windshield-internal dipoles work as well on FM as a
> good external vertical whip of the proper dimension. They are not
> omnidirectional, nor are they vertically polarized, both of which are
> helpful for FM in a moving car. The folded ones may have different
> characteristics that overcome these drawbacks, I don't know for sure.
>
- at all almost every car AM radio since dirt has
- used a ferrite- or air-core coil antenna;
H U H ?
- far more effective than a whip or wire ever could be.
- Especially the ferrite, it gets you what a whip cannot
- ~ full wave resonance and high relative gain.
- Match that with a quality AM radio and you'll
- have a nice MW DX machine in your car.
- I love listening to stations on the Great Plains
- when driving overnight to Yellowstone :-)
-
- Bruce Jensen
DEFCON 88
--------------------------------
[...]
. . . . . . . . . . . . . . . . . . . . .
>
>
> Moreover, they are not likely the AM antennas at all - almost every
> car AM radio since dirt has used a ferrite- or air-core coil antenna;
> far more effective than a whip or wire ever could be. Especially the
> ferrite, it gets you what a whip cannot - ~ full wave resonance and
> high relative gain.
>
What? Car radios use coil/loop antennas for AM? I think you're
mistaken. The metal car body would seem to be a bad environment for
such an antenna.
bpnjensen
wrote:
> "bpnjensen" <bpnjen...@yahoo.com> wrote in message
OK OK! I get it :-) That's what I get for not paying attention in car
radio class :-)
dave
Since dirt until very recently AM car antennas have been active whips.
Note the very tiny center conductor in a car antenna co-ax; because the
impedance is so high at 1 MHz. The 31" whip, plus the lead, is your AM
antenna. Same as an MFJ or Stoner Dymek active. No difference. Short
whip into an FET. The old radios had slug-tuned PTOs. Maybe that's
what you're thinking of.
dave
>
> OK OK! I get it :-) That's what I get for not paying attention in car
> radio class :-)
You're not going to like my post either then.
I use mobile 3G/4G for my in-town listening (sorry 'Dwardo) and Sirius
when I'm away from civilization. Still listen to the AM at night.
Always will.
bpnjensen
You're right, I'm a dufus. I actually knew that, but a brain fart
caused me to go sideways. Apologies all around.
Broofus da Doofus
bpnjensen
Oh, I don't mind :-) Just wrote a reception report for REE via Costa
Rica, so I'm happy.
david.h...@gmail.com
> I've seen some car radio whip antennas that look like they have a wire wrapped
> around them. The wraps are not close but lazily spiral down the length of the
> antenna.
>
> Does this help reception? Is the coil attached somehow to the car or just the
> antenna itself?
>
> twitch