Navtex/DSC problem?
Good morning....
I have two Kiwi receivers on the same site, the first and second versions.
Using the DSC extension I noticed that the Kiwi v.2 has decoding problems as it does not seem to respond to the signal to be decoded, I also tried applying the [+errs] option to check that at least the signal was treated by the internal decoder. I would add that on the 16804.5 frequency I cross-checked with YADD and found that on the Kiwi v.2 I only got error messages while on YADD the messages were decoded.
Comparing the same frequency with the Kiwi v.1, which has a decidedly less performing antenna and with the same settings with the exception of the [+errs] I noticed that many more messages are decoded compared to version 2.
Both devices are updated to the latest version of the management software.
I would like to know the reason for this problem?
Comments
Well, hard to say. But all those parity errors and "no end-of-sequence (EOS)" on the Kiwi-2 probably means an impaired receiving condition compared to the Kiwi-1. That is most likely a mistuning of the signal causing the FSK filters to give noisy output. Look carefully at the waterfall to make sure the black-and-white markers are centered on the FSK signal. Zoom in if necessary to see this clearly. Compare the two Kiwis. Does the Kiwi-2 have GPS frequency calibration?
...Both Kiwis are GPS calibrated.
The only difference between the two Kiwis in the first post is given by the fact that the Kiwi v.2 was in 3 channel mode [More bandwidth] while the Kiwi v.1 was in 4 channel mode [Kiwi classic].
Today I brought the Kiwi v.2 back to 4 channel mode [Kiwi classic] the result is what can be appreciated in the attached image, always taking into account that the Kiwi v.1 has a less performing antenna than the Kiwi v.2.
In light of the above, do I think it is a problem with the audio signal in the 3-channel version?
In light of the above, do I think it is a problem with the audio signal in the 3-channel version?
Sure seems that way. I'll look into it. Thanks for the clarification.
If I use the FSK extension "scope" mode for a test DSC signal I can clearly see in 20 kHz (3ch) mode the zero crossing detector is not quite right compared to 12 kHz mode. This might explain why it works on very strong signals but not weaker ones.
The problem is that I didn't write that part of the FSK code and I don't understand it. There is nothing in it that is 12 kHz specific. The parts that are sample rate specific are getting the correct values set in 12 vs 20 kHz (actually 20.25 kHz) mode.
So I don't know. This means it will require a lot of time to diagnose and that means it falls much further down the priority list.
Okay!
It was considered a problem report.
At the moment I remain in 4 CH mode. if it is resolved then I will try again in 3 CH mode.