[BC] The Future / Signal

[Mark Humphrey]

On 12/3/06, Robert Meuser <Robertm at broadcast.net> wrote:
> The horizontal was best.  At the time there was some choice and I
> strongly recommended to my customers to choose horizontal.

Many European-made cars have their antennas mounted on the roof and
angled back at 45 degrees; not only does this appear "stylish", but I
assume it improves the reception of horizontally-polarized FM signals
--- although I wonder if the H-pol azimuth pattern has any deep
"nulls", for instance, directly behind the vehicle.   Anyone know
where we could find test results on automotive receive antenna
patterns?

I've observed that the FM stations in Germany are almost all
exclusively H-pol; most are using high-gain Kathrein panel antennas
with 1/2 wave spaced dipoles, although I've seen some "batwing" FM
antennas and skewed H-pol yagis at translator sites.  The broadcast
engineering community there seems steadfastly opposed to any change
from the H-pol standard, while many other surrounding countries have
settled on "mixed" polarization.

However, V-pol appears to be the standard throughout Europe for DAB.
Perhaps the increased multipath actually improves coverage because it
fills 'dead spots".  I guess with COFDM, short reflections are not a
problem, as they would be with FM.

About 20 years ago, I did some polarization experiments at WRTI's
translator in Reading, PA.  After turning the transmit antenna (a pair
of 5-element Scala yagis skewed 90 degrees) from H-pol to V-pol, the
signal strength in car receivers improved dramatically, "picket
fencing" was reduced, and a substantial number of listeners commented
on the "power increase", although we hadn't changed the TPO.  This
convinced me that vertical beats horizontal (at least where most cars
have fender-mounted vertical whips) but maybe our results would have
been much different with the Euro-style angled antennas.

Mark