Ryan Logan wrote:
On Sat, 16 Apr 2005, Frank Dresser wrote:
"Ryan Logan" wrote in message
ocaldomain...
I was listening to my SW radio and was just surfing through channels when
I found one on the 31m band around frequency 10.00 Mhz. It was some kinda
christian evangalance show. Anyway, I had been listening for maybe 5
seconds to a good strong signal when I started hearing beeps very quietly
in the background.... Kinda like maybe picking up the phone on a 300 baud
modem. That's the best way I can describe it, which may not be very
accurate as I haven't heard a 300 baud modem in.... ever. Anyway, this is
the first time I've heard this since I've been listening to stations and
it sounded kind of odd. Anyone know what this could have been?
My first guess is the interference came from a SW utility station. There
are still alot of digital signals transmitted on SW. Some utility stations
share frequencies with some SW stations and some receivers might also be
sensitive to spurious out of band signals.
Here's a page with recordings of some utility signals:
http://www.wunclub.com/sounds/index.html
This is from:
http://www.wunclub.com/
Frank Dresser
It soudned EXACTLY like that Radio Teletype (RTTY) sample. BTW I run a
Text Based BBS that you can telnet to at bbs.ryan42.com. I have heard of
packet radio, where you can connect to other ssystems over a radio band.
is that similar to this?
I'll leave it to somebody else to explain the tech specs of RTTY, but if
you were indeed hearing an RTTY signal, it was probably an image of a
station on another band, caused by the IF mixer in your radio. The
station you were probably intending to hear was a WWCR outlet, this one
on 9985. Most images on SW radios appear 910 khz away from the actual
station, since the IF of most radios is 455 khz. That would make the
actual freq of the RTTY on either 9075 or 10895 if my mental math is
correct. If you hear RTTY on the WWCR frequency again, tune to either
9075 or 10895 and see if you hear the same signal. If you do, it
probably will be VERY strong meaning it's local to you. If this is the
case then it's an IF image created by your radio's internal circuitry
and there's little you can do about it. IF=Intermediate Frequency, the
frequency that all radios use in their internal circuitry in the process
of turning a radio wave into an audible sound. IF for AM/SW is usually
455 khz, a standard that dates all the way back to the early days of
tube radios and that remains the same because of social inertia. IF for
FM is 10.7 Mhz, another standard developed early on (early in FM's
history in this case) and that stubbornly refuses to change.
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