I thought riometers/sounders used FMCW emission, slewing in a quasi-linear 
fashion from 2 or 3 MHz up to about 20 or 30 MHz at around 80 to 100 kHz/s or 
so.  Are there ionospheric chirp sounders that emit for several seconds at a 
time centered on the same freq as shown in the spectrogram at 26.5 MHz?
--
Dave
On 10/23/25 10:42, 'Lester Veenstra' via Society of Amateur Radio Astronomers wrote:
> CW Chirp ionosphere radar
>
> Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
>
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> *From:*
sara...@googlegroups.com [mailto:
sara...@googlegroups.com] *On Behalf
> Of *Dave Typinski
> *Sent:* Wednesday, October 22, 2025 11:36 PM
> *To:* 
sara...@googlegroups.com
> *Subject:* Re: [SARA] Radio Jove Question
>
> Those look like HF radar to me.  Normally they hop all over the place
> frequency-wise, but that operator seemed to have a fetish for 26.5 MHz.
>
> I'm thinking of the stuff that sounds like this:
> 
https://radiojove.gsfc.nasa.gov/library/multimedia/audio/rfi/hfradar1.wav
> --
> Dave
>
>
> On 10/22/25 14:34, kb3puw wrote:
>
>     Thanks, I will keep looking.  I see these little blocks in your data.  I
>     assume they are the digital burst transmissions that I see a lot of in this
>     frequency band (they are quite recognizable if you demodulate them as AM)?
>
>     On Tue, Oct 21, 2025 at 9:28 PM Dave Typinski <
dav...@typnet.net
>     <mailto:
dav...@typnet.net>> wrote:
>
>         We observed a Type III solar radio burst at 1909 UTC on the 20th.  Could
>         be what you observed; hard to say for sure without timestamps.
>
>         In the spectrogram below, Time UTC is on the horizontal and freq in MHz
>         is on the vertical.
>         --
>         Dave
>
>
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