[Aavso-sid-list] Software longwave receiver

[P. W. Schnoor]

Hi Chris,

You wrote:
>  
>     You might do better with one of the VLF radio  chips? Maybe an audio 
> preamplifier? Or a few transistor pairs connected in  series? Alternatively, an 
> OP37 has bandwidth to 200kHz. OP27s are not great  over 30 kHz.

Thanks for that hint! I found the op37 data sheet. 63 MHz GBP 
compared to 8 MHz (op27) indeed looks somewhat better...

>     There seems to be something wrong with the spectrum  at 
> _http://home.arcor.de/df3lp/spec/2007-03-29_one_spec.png_ 
> (http://home.arcor.de/df3lp/spec/2007-03-29_one_spec.png) 
>  
>     The 60.0 kHz Rugby time signal seems to be  recording at 60.5 kHz. There 
> is no FM/AM modulation on this signal - it is  on/off modulation. It is strong 
> over your area. 

No, this peak in the single spectrum is not MSF. It's of unknown 
source. MSF shows a very narrow peak and is covered there by the 
60KHz grid line. It is clearly visible and right on the line in 
the waterfall displays. Look at the single spectrum from today, 
0730 utc:
http://home.arcor.de/df3lp/spec/2007-03-30_0730.png

> DCF77 seems to be coming  through strongly and is correctly 
> indicated. 

Yes, and HBG at 75KHz too but faint. Compared to my old single 
band receiver with tuned antenna and conventional fet-preamp the 
receiving of HBG is unsatisfactory. Broadband design is a real 
challenge...

I was surprised that nulling out DHO at 23.4 KHz as far as 
possible uncovered NAA, Maine at 24.0 KHz.
See: http://home.arcor.de/df3lp/spec/spec_2007-03-27.png at 
16:45 utc.

BTW: Iceland at 37.5 KHz is back on air (the radial ground 
system looks impressive at google earth)

Greetings from 54°N/10°E
Peter