*Those CODAR systems are known to intrude on the bands from time-to-time.*
*They're usually pretty good about getting off the band if someone
complains.*
*(Coastal Ocean Dynamics Artificial Aperture Radar.)*
On Sat, Feb 22, 2014 at 12:39 PM, Karin Anne Johnson <
karinann@tampabay.rr.com> wrote:
> Hello Group:
> This is not so much an RFI issue, but more of a curiosity question. I've
> noticed for quite some time now that there appears to be what I would call
> sweeper signals that are quite strong on ten meters. Mostly in the CW
> sub-band.
> These signals start mostly around 28.200 MHz and sweep down in frequency
> stopping around 28.000 MHz. It is difficult to actually measure the exact
> start and stop frequencies as they sweep pretty fast. I'm looking at them
> with PowerSDR. The signal strengths vary, with most of them being about
> -80
> to -90 dBm. The antenna I am using is a simple ten meter dipole about 30
> feet in the air. I only see these signals during the day time when the
> band is open. I've never seen them after the band closes here in Florida
> after dusk. As usual I've powered off the entire house and they are still
> there on the spectrum display. Has anyone else seen these signals? What
> might they be? Ionsondes, Over the Horizon Radar of some type, Ocean
> mapping RF source? In the past I've found that Ionsondes usually sweep up
> in frequency, and
> cover a much broader range of frequencies. On a similar note, I've also
> seen what might best be described as wideband data bursts, lasting from 2
> to
> 3 seconds on a range of frequencies just below ten meters. Between about
> 27.500 MHz and 28.000 MHz. Looking at these signals on the spectrum
> display
> it almost seems that there is a master/slave relationship between some of
> these data burst signals. As one stops sending it is observed another one
> starts sending. These also only observable during the daylight hours. I
> know that the 27 MHz band used to be allocated to ISM devices so maybe that
> is what these signals are related to. I know, too much time on my hands
> and a mystery to be solved. Can't resist the urge. Anyone interested in
> positing a guess?
>
> Regards,
> Karin Anne Johnson K3UU
> Palm Harbor, Florida
>
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