[BC] The Future / Signal

[Dana Puopolo]

Two station in RI were combined into an ERI slant linear (dipoles aligned at
45 degrees) antenna. It kicked ASS!! They replaced it with a cogwheel some
years ago, but their signals aren't as good these days....
Craig Healy can elaborate...Craig?
-D

 

------ Original Message ------
Received: Sun, 03 Dec 2006 12:47:04 PM EST
From: Robert Meuser <Robertm at broadcast.net>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] The Future / Signal

I think the difference might be that a low powered translator might be 
working on a more pure line of sight path.  The reason that the Germans 
are so against anything other than horizontal polarization is the test 
that was conducted in the 70s. There was a paper from Kathrein written 
by Marvin Crouch which documents a detailed research project dealing 
with various polarizations there. I have tried to locate it on the web 
to no avail so far. One of the things pointed out was that once the 
signal hit the metallic auto body, the polarization was random anyway. A 
similar test was conducted in  Saskatchewan Canada in the early 80s with 
similar results.  In that test a Kathrein panel antenna was arranged so 
that it could produce CP, Horizontal, Vertical, or elliptical 
polarization. Those tests produced similar results. This is the reason 
the CBC in Canada has built horizontal only stations for their network. 
Not all their stations are HP. If an existing CP station was not 
scheduled to be rebuilt, it was left alone. A number of commercial 
stations mostly C1 or C's up there are Horizontal only as well, notably 
in Ottawa and Halifax.

R


Mark Humphrey wrote:

> 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
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