[Lowfer] 650 khz Cuban wobbler

[craig wasson]

This one looks like a malfunction - as mentioned the normal audio
fades out just before it appears.  I think it's an oscillation in the
audio stages - most likely it is sweeping back and forth outside the
audio bandpass for a while, then narrows down to be in the passband
until it drops to zero.

Back in 2003 someone noticed a "woodle" in radio station KFI's carrier
frequency - a very noticeable recurring zigzag.  Some thought the
shifting was carrying some secret hidden signal.  I think it ended up
being a factor of how the frequency stabilization worked, and maybe
something was broken.

Most AM stations and NDBs show a distinct sawtooth pattern when the
crystal oven goes on and off, plus some day/night ambient temperature
caused variation.  You can use this to identify a specific carrier out
of the myriad of carriers on some frequencies.  There is a yahoo group
"MWOFFSETS" that discusses this and posts unique patterns that people
can use to identify a specific station.  The variation is usually a
fraction of a Hz, but easily monitored using speclab.  I've used this
to identify dozens of LWBC stations although not all have published
offsets so you have to use the signal variation along the grey line
over a week or so to determine exactly which station it is.

If you thought monitoring QRSS beacons was esoteric - monitoring
carrier offsets is even more so.  It can take a week or two to be
confident you've identified a particular station if you are just using
time of day shifts and grey line signal strength changes, or for
stations that are not on 24-hours a day.  Luckily with an SDR you can
monitor many carrier frequencies simultaneously and record a week of
data on a single .jpg image so it's not all that time consuming.  Some
of the more powerful European stations have a detectable carrier
during mid-day even in summer.

Craig - N6IO


On Tue, Mar 12, 2013 at 12:52 AM, KD7JYK DM09 <kd7jyk at earthlink.net> wrote:
> : Nice!  Sure wish we could find out for sure what, why and where it is.
>
> Does it sound like anything to the ear?  What if sped up?  There must be
> something to it, it looks too good for a malfluctuation.
>
> Kurt
>
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