Архив за 17.04.2019

Sudden Problems with NOAA Decoding

I've been receiving lots of good NOAA images recently, and having a blast doing it! But today, I ran into a bit of a problem with decoding.

I went out to receive a southbound NOAA 18 this morning, set up my gear, waited for the pass, hit record, same as always. Pretty much the same as the day before, where I recorded this less than perfect image from NOAA 19. But hey, it was usable.

Today, I received this monstrosity. Post processing in WXtoIMG, including slant correction, did nothing. This was the best I could do using noaa-apt. Better, but unusable for any sort of post processing. I thought it was a one off problem. Then I recorded NOAA 18 and NOAA 15 on northbound passes this evening (raw unprocessed images shown here). Processed, they look better, (18, 15) but not good enough for post processing to work there.

Now, I've done some research on what might have caused this, and I have some theories. This site says that too many background processes running on the PC doing the decoding can lead to loss of synchronization, and changing recording volume during recording can cause banding. The latter (volume change) I am guilty of for today's NOAA 15 pass. I'm fairly certain I didn't screw with the volume on 18's southbound pass, and I certainly didn't do so on 18's northbound pass. But even if I did, could it cause these issues? 15's decoding was already wonky before I changed volume. I also watched 15's live decoding as I changed volume, and it didn't seem to affect it. I've recorded a dozen passes before this, and never had any of these issues.

Can too high recording volume cause this? I am usually hovering somewhere around 80, but never had issues with this before (see my previous successful decode).

I received these images using a new V-Dipole, but yesterday's one was its first reception, and it went without issue, so I'm doubtful it's that.

I've had a fairly good SNR of between 25-35 for these passes, and the raw audio does not sound anyhow different.

Have any of you run into similar problems? What could be causing these reception / decoding issues?

Album

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KerberosSDR • Re: 90 deg and Sample Size

Tamas added the calibrate 90 button, but it's currently not fully complete, so I might actually remove it from the next version.

The idea is you could have an external signal source that you place at 90 deg of your antenna array, and calibrate with that. Using an external source would remove any skew from the antennas/cables etc. Currently it seems to calibrate at 0deg though.

The sample size boxes are placeholders at the moment, and do nothing. In a future version that someone is working on we'll be able to set the sample size, but at the moment it's fixed to the block size.

Statistics: Posted by rtlsdrblog — Wed Apr 17, 2019 11:43 pm


KerberosSDR • Re: Pi image issues…

All the images are shrunk down to 7G, so they should fit on all 8GB cards, unless yours is really bad?

Are you able to connect to the KerberosPi WiFi?

Statistics: Posted by rtlsdrblog — Wed Apr 17, 2019 11:38 pm


KerberosSDR • Re: Share your results

mdacosta wrote:
Wed Apr 17, 2019 5:11 pm
After several hours of fine tuning, I'm able to get a nice bearing on the ULA (linear array) but, could not get the UCA (Circular array) to get a nice bearing. Anyone else having the same issue?

Are we sure the drawing and info on the UCA is good?
Antenna radius = λ*s or should it read
Antenna spacing = λ*2

Thanks
What frequency, spacing factor and antenna radius are you using? λ*s is correct.

Statistics: Posted by rtlsdrblog — Wed Apr 17, 2019 11:36 pm


Comment on LimeRFE: A LimeSDR RF Front End for Ham, Cellular and Wideband Networks by Dana

Yipe!!! YES!!! 222 and 902 ….thx Dave 73

Comment on LimeRFE: A LimeSDR RF Front End for Ham, Cellular and Wideband Networks by Dave N2OA

In addition to 220 – 225 MHz don’t forget 33cm 902-928 MHz

KerberosSDR • Re: Clock oscillator on KerberosSDR?

Thanks for getting back to me. I'll post my results when I've managed to do something with it. Now to make some antennas ...

Statistics: Posted by Chris Eilbeck — Wed Apr 17, 2019 10:36 pm


Comment on LimeRFE: A LimeSDR RF Front End for Ham, Cellular and Wideband Networks by Dana VE3DS

Hey you guys MISSED filters for 222 – 225 MHz!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Is there an SDR M.2 or any addon i can put into a laptop/netbook?

I want a mobile SDR without have the annoyance of carrying round a USB stick and having to accidentally break it by catching it on something.

submitted by /u/HS524
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Comment on LimeRFE: A LimeSDR RF Front End for Ham, Cellular and Wideband Networks by Earnest Hart

Very interesting. Looking forward to learning more about this. 73.

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