Shifted Psd, no visible shifted PSD level

Posts to forum

http://drm.sourceforge.net/forums/index.php?showtopic=156

 

Feb 13 2006, 11:09 PM

Greetings

I specially send very low signal to audio input.
Dream can work excelent with very low level audio signals -100db PSD

http://www.smail.lt/~ncss/regen_info/3995_-100db_To14khz.jpg

But no visible shifted PSD level.

http://www.smail.lt/~ncss/regen_info/3995_...oShiftedPSD.jpg

One can increase Y range in shifted PSD level.

I want test minimal pure radio signal level enough for software decoding.
Its need for long distances DX and receive 1296Khz BBC and other MW stations
on 80m delta loop

http://www.smail.lt/~ncss/regen_info/1296_-110db_To14khz.jpg

Best regards;

Saulius.

 

 

Feb 14 2006, 05:14 AM

Your screenshots are amazing, and you have put together an even more amazing set of hardware.

I have best results with an input level where the Input PSD has the top of the DRM signal at the -60dB line.

In the Dream main dialog, there is also an input level meter showing a transition between red and green

at about -12 or -15 dB (see screenshot attached). With the signal at that transition, the input PSD is

usually at the level I mentioned earlier, and Dream performs best for me.

Josh Moore
HCJB World Radio

This post has been edited by servantcoder on Feb 14 2006, 05:17 AM

Attached File

 levelmeter.png

 

 

Feb 15 2006, 05:27 AM

Thank you Servantcoder for estimation.

Such (today Radio Luxemburg in Lithuania)

30 db atteniuation from antenna
http://www.smail.lt/~ncss/regen_info/7295_...oShiftedPSD.jpg

10 db atteniuation from antenna
http://www.smail.lt/~ncss/regen_info/7295_...oShiftedPSD.jpg

1 minute Frequency offset after 60 min. valves heating if no interference
from power sources:
http://www.smail.lt/~ncss/regen_info/7295_..._FreqOffset.jpg

Impulse response
http://www.smail.lt/~ncss/regen_info/7295_...lseResponse.jpg

10 db atteniuation from antenna
About same time BBC on 7320Khz and visible symetric
7295Khz suppresed sideband interference on 6 ... 9 khz
total suppression consist of sum
LC + IQ DRM Decoder inside + software
supressions

http://www.smail.lt/~ncss/regen_info/7320_...Visible7295.jpg

and prior screenshots obtains from this system:


http://drm.sourceforge.net/forums/index.ph...topic=155&st=0&


Question for programmers:

when Dream started in this I/Q input positive 3 mode
routine how much
easy ( or not) - eficiently software decoding signals
compare to one channel 0 or 1 Dream mode
or 2 (default) sum mode ?


Best regards;

Saulius.