No Decode.

4 posts / 0 new
Last post
Anonymous (not verified)
No Decode.

Hi John, M1ENI

Tried to reply to your "Decode" post but forum reply seems to be broken so I will try this way.

Well the essential things required for a good decode are:

1. Your computer clock must be set correctly, errors greater than + or - three seconds will prevent both RX and TX decoding).
(Quick check are the received signals on the waterfall, starting exactly on the two minute markers)?

2. You are using Upper Sideband, the correct sideband for WSPR,s (LSB won't decode)

3. The grey box showing Rx Noise should be showing 0 dB but, it is not critical +- 10 dB will work ok.

4. Frequency is critical, only to the extent that the WSPR prog will not decode anything outside Plus or Minus one hundred hertz of the 1,5kHz audio tone frequency so selecting USB setting the tranceiver dial to 10,138,700 should receive the WSPR band 10,140100 to 10,140,300, a signal on 10,140,200 should produce an audio tone of 1,500 Hz. (No RIT or XIT offset)

So assuming Correct Timing, USB Sideband selected, RX Noise Level (0dB) adjusted, and Dial Frequency correct, the next step is to look at the software and the computer.

What Version of WSPR's, what operating system and brief details of CPU and memory?

I suspect from your description of the problem that the trouble lies in slow processing of the received data.

The WSPR transmission has 50 user data bits, 112 error correcting code bits, combined with another 162 bits of synchronizing symbols fed into the decoder and error correction process.

When the signal is nice and clean a single pass through the decoder may produce a good decode.

When the received signal is noisy, distorted, or suffers interference the data is looped through the decoder many times, the more times the longer the decoding time.

When the signal is badly distorted it may do up to 20,000 loops through the decoder, which depending on the computer speed and other processing being done can take minutes.

You can see in this printout extract, the 2nd last figure in each line is the number of decode loops each decode required. (1 to 19860)

100929 0816 6 -23 0.0 10.140237 JL1DLQ PM95 37 0 10276 40
100929 0818 14 -18 2.1 10.140199 F5UL JN35 37 0 1 0
100929 0820 4 -26 -0.1 10.140182 WW7Y DN40 37 0 12 0
100929 0820 5 -25 -0.7 10.140193 KF6I DM13 30 0 19860 17
100929 0822 27 -3 -0.2 10.140164 WA2YUN RK39 37 0 1 0
100929 0824 5 -26 -0.6 10.140193 KF6I DM13 30 0 5540 0
100929 0828 8 -21 0.4 10.140191 JQ2WDO PM95 37 -1 12710 12

So a slow decode ties the computer up for a long time, reducing the chance of decoding other signals.

Hit Ctrl + Alt + Del and select performance to see your CPU usage, if you are hitting 100% for long during a decode you have a problem.