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Author Topic: Pulling in weak PSK signals  (Read 5665 times)
N6SBN
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« on: May 26, 2013, 09:23:36 PM »


   If a PSK signal is weak, do I gain any better reception turning up the AF gain?  I can see an increase in snow on the screen.  Not sure what is the smart way to operate.  So, how much snow on the waterfall is detrimental?  Thanks in Advance.
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W6UV
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« Reply #1 on: May 28, 2013, 11:05:05 AM »

Turning up AF gain probably won't help much. What you need to do to pull out weak signals is to increase their signal-to-noise ratio (S/N). Turning up the AF gain increases the signal level, but it also increases the noise and the ratio stays the same.

Some ways to increase S/N are: use a directional antenna to enhance the intended signal and attenuate signals (and noise) coming from other directions; use a low-noise receiving antenna, such as a beverage or magnetic loop.

Using your rig's noise reduction features, such as NR and NB, probably won't help as these tend to distort the signal.
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N4CR
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« Reply #2 on: May 28, 2013, 12:32:59 PM »


   If a PSK signal is weak, do I gain any better reception turning up the AF gain?  I can see an increase in snow on the screen.  Not sure what is the smart way to operate.  So, how much snow on the waterfall is detrimental?  Thanks in Advance.

Yes and no.

No, increasing the volume level will not increase the signal to noise ratio, which is the baseline for discriminating a signal out of ambient noise. A better antenna, more antenna height, less interference noise can all help.

Yes, most decoders work better when they are fed a 'strong enough' signal. So if you have the volume level too low going into the decoder, the decoder has a more difficult time decoding the spectrum you are sending it. I have found over the years of playing with pskreporter.info that I got a higher number of decodes per day if I have the audio input pushed as far up as possible without running into signal overload.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
N4UM
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« Reply #3 on: May 30, 2013, 05:09:47 PM »

Set your filter to as narrow a range as possible in order to increase the s/n ratio.  With psk31 you should be able to set your filter width to 50-100hzThis should improve copy
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AA4PB
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« Reply #4 on: May 30, 2013, 05:38:45 PM »

Since the PSK31 software has a very narrow DSP filter ahead of the decoder, narrowing the IF bandwidth of the receiver will not improve the signal to noise ratio seen by the decoder. What a narrow IF filter **will** do is to cut out adjacent strong signals before they push the AGC and reduce the receiver gain. If there are no signals in the waterfall that are significantly stronger than the desired signal then you shouldn't notice any difference is printing ability whether the receiver IF filter is 3KHz wide or 50Hz wide.
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N6SBN
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« Reply #5 on: June 02, 2013, 04:32:47 AM »

  I've tried narrowing the waterfall with the filters.  It does help when there are booming adjacent signals.     I tried WSPR and noted that my vertical antenna doesn't have the range that the other station have, so, I may try a ladder line dipole.   It's frustrating seeing a moderate signal on the water fall that doesn't produce text.   N6SBN
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