Re: WJIB-AM 74 music on weekends???

[Aaron Read <aread@speakeasy.net>]

At 05:34 PM 8/19/2003, rogerkirk wrote:
>"Dan Strassberg" wrote:
> >...In addition, I never knew that air conditioners affected AM
> >reception. The motors are ac induction motors and as far as I know,
> >they do not produce RFI. What else is there in an air conditioner that
> >could cause interference?
>
>IIRC, modern air conditioners have a small micro-chip to control
>temperature, fan speed and run the timer.  That alone cold provide
>a lot of hash.
>
>Is it possible that the Green, Blue and Orange lines and their
>DC motor controllers could be making RFI?

I believe the newer Red Line cars and the new-new Green Line cars (at 
least) use electronic braking (reversing the motors' magnetic fields as if 
they were trying to spin the motors backwards).  You can hear it as they 
pull into a station with the electronic-sounding wail that decreases in 
pitch over six or seven steps...almost like a gearshift.

Those things put out an INSANE amount of RFI....I was deafened one day 
listening to WBZ on my walkman a few years ago on a Red Line T.  It's even 
audible in the FM band.

But that sort of RFI wouldn't penetrate from the tunnels up into Quincy 
Market.  Not enough to make that much hash.


--------------------------------------------------------------------------------------------
Aaron "Bishop" Read             aread@speakeasy.net
FriedBagels Consulting          AOL-IM: readaaron
http://www.friedbagels.com      Boston, MA