[DML] Re: Antenna Technology Idea

[Marc A Levy <malevy@xxxx>]

I have some experience with Radio and Antenna technology, having worked
on Cordless Telephone projects. I am sure some Ammeter Radio (HAM) guys
on the list may be more qualified to talk about this than me, but my few
years working on Cordless Phones did teach me a few things.

While it is true that radio receiver technology has improved over the
years with more accurate local oscillators, digital tuners and higher
tolerance components, I don't think this will have a huge effect on
improved radio performance in the D.

I have never opened up the stock Delorean radio, but I expect that in
general the radios are not as good as they were 15 years ago. Age effect
the stability of the components used to tune the radio. The radio
could be re-tuned with the proper equipment, but sometimes in the long
run this will cause more problems.

Sad to day, but most of the stock stereo's found in todays new cars are
better than after market replacements as far as radio reception goes. 
This is not because they have come up with some new wiz-bank radio
technology, it is because they are starting to use a not-so-new idea of
antenna diversity.

Most of the new cars have multiple antenna's (usually two). The
antennas are designed and placed such that in some cases one will be
better than the other. Inside the radio, there is a RSSI circuit that
can decide which antenna is getting a better signal, and use that one. 
This is system is running all of the time, so if your turn a corner and
the environment is such that the "inactive" antenna is better, the radio
switches to that one.

This all works because of the way radio signals travel, and bounce. The
Physics involved with all of that is out of my scope.

The technology has been around for many years. The first time I saw it
used in a car was my parents 1988 Mazda. There were two antennas in the
car, and the radio never had static. On the front of the radio was a
label "Antenna Diversity".

Now, Back to the D. Most of the work of Antenna Diversity is done by
the receiver itself. I have not yet seen any after market stereo
companies that offer Antenna Diversity, so unless someone is going to
redesign the radio receiver, I don't think it is going to happen.

If your goal is to just get rid of the mast antenna, then a dipole
antenna under the louvers MAY work, but the antenna will now be
horizontal instead of vertical. This changes the property of the
antenna pattern such that when you turn a corner a station that was
clear before will quickly be gone. This is of course THEORY, and may
work in practice anyway depending on the RF environment in your area. 
Most of the Diversity systems I have seen use both a Vertical and
Horizontal antenna, but a horizontal alone (in THEORY) will not be as
good for this application.

On that same idea, the windshield antenna is both horizontal and
vertical. It travels vertically up the center of the windshield, and
then splits left and right horizontal across the top. This is a similar
design to the freebie antennas that come with home stereo systems. I
have never been able to get a decent signal from those antennas here in
Central New Jersey. With all of the RF noise in New Jersey, those
antennas receive TOO MUCH!

And after all of that, your back were you started. Might as well just
try it. I am sure you can find some formulas (Or finished designs) on
the net to get the proper length for a dipole to cover the standard
radio frequencies.

Mike Substelny wrote:
> 
> DMC Joe wrote:
> 
> > . . . Radio sensitive technology has improved drastically since
> > the late 70's when the factory installed units were designed. [SNIP]
> 
> > I would like to see if today's auto radio technology coupled
> > with the windshield antenna would make for satisfactory reception.
> 
<SNIP> 
> I have often wondered if this same technology could be used to build an antenna inside or
> under the rear sunshade louvers of a DeLorean. That would achieve both the look Guigaro
> intended and the radio performance owners expect.
> 
> Do any electrical engineers out there feel up to the challenge?