Peter,
Sad to say, but winding toroids and sticking them around will not do
anything to eliminate the IBOC crud that you have been hearing. I live
near Cedar Rapids, IA, and station WMT, at 600 on the AM dial, puts out
IBOC sidebands that can be heard when trying to hear the old WMAQ in
Chicago, at 670. (I'm an ex-Chicagoan who now lives among the corn and
soy bean fields.) The only real "cure" is to use a radio with variable IF
bandwidth to copy stations that are in the "IBOC zone" of other stations.
Since most radios do not have such a feature (except communications grade
receivers, such as what hams use), some broadcasters who own multiple
stations in closely situated markets have found out (the hard way) that
IBOC from one of their stations may cause severe interference for
listeners on other stations that are within 30 to 70 kHz of either side of
the offending station. In such cases, some stations have killed their
IBOC transmissions under orders of their owners.
The next time you want to listen to WGN on a trip, try using the general
coverage feature of your mobile ham rig and forget the car radio. (Note:
You'll probably want either a 160m or 75m mobile antenna on the vehicle to
provide signal input to the rig.) Adjusting the IF passband should
eliminate most of the IBOC problem for you.
The better SWL receivers may also be useful, and I can tell you that the
GE/RCA "Superadio" has "Narrow" and "Wide" IF selectivity positions on its
front panel. I own one, but the set is such a piece of junk otherwise
when used on the AM band that I hesitated to mention it at all. In short,
the answer to your question is not ferrites and turns, but re-designed IF
strips and maybe DSP, as well.
73, Dale
WA9ENA
Peter Laws <plaws0@gmail.com>
Sent by: rfi-bounces@contesting.com
09/07/2009 01:06 PM
To
rfi@contesting.com
cc
Subject
Re: [RFI] Washer RFI/EMI
On Mon, Sep 7, 2009 at 10:26, Jim Brown<jim@audiosystemsgroup.com> wrote:
> BTW -- another component of increased noise on the AM broadcast band is
IBOC
> -- In Band On Channel digital broadcasting -- which greatly broadens a
> station's sidebands and interferes with adjacent channels.
Drove from W5 to VE2 last summer and tried to listen to WGN 720 kHz
after dark for Cubs games. Even though 'GN is a 50 kW station on the
remnant of a clear channel, it was impossible to listen to in some
places due to that crappy IBOC stuff.
Question is, what size toroid gets rid of this and how many turns
through it??? :-)
--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!
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