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What's the Weakest Signal You Can Get a Response From?
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When working WSJT-X, what is the weakest incoming signal you expect to get a response from?
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I'm running a QDX and a QMX, each putting out 2-4 W depending on the band. I find that I rarely get a response from anyone unless their incoming signal is better than -10 dB. That sort of makes sense. If they're putting out 50 W I should be 11 dB or so below them, and -20 is the practical limit, so assuming reciprocal links the incoming signal should be -9 or better. Obviously there are people out there not running 50 W, but apparently not many. I've run numerous antennas and various bands and always seems about the same.
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I've convinced myself that this is normal, but is that consistent with other people's experience using a 4 W transmitter? |
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Mike Black
QRP (< 5W) is a challenge.
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hamspots.net and pskreporter.info both show lots of low SNR for your transmissions. Mike W9MDB On Sunday, September 22, 2024 at 01:00:17 PM CDT, pgramsey, N9LFF via groups.io <pgramsey@...> wrote:
When working WSJT-X, what is the weakest incoming signal you expect to get a response from? ? I'm running a QDX and a QMX, each putting out 2-4 W depending on the band. I find that I rarely get a response from anyone unless their incoming signal is better than -10 dB. That sort of makes sense. If they're putting out 50 W I should be 11 dB or so below them, and -20 is the practical limit, so assuming reciprocal links the incoming signal should be -9 or better. Obviously there are people out there not running 50 W, but apparently not many. I've run numerous antennas and various bands and always seems about the same. ? I've convinced myself that this is normal, but is that consistent with other people's experience using a 4 W transmitter? |
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Hi,
the precise number for the receiver could be the MDS or the sensitivity. It is measured at the receiver input.
MDS - the minimum discernable (or decodable) signal
Sensitivity - the signal that is a predefined number of SNR.
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When it comes to your question as how it works on the air, how you can make the least possible QSO than you have to calculate more things.
- from you --> the correspondent
your: TX power, antenna efficiency, --- propagation, QRM, --- correspondent's: antenna efficiency, RX sensitivity.
- from him --> you:
his: TX power, antenna efficiency, --- propagation, QRM, --- your: antenna efficiency, RX sensitivity.
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In the QSO all these are in series, so whatever parameter fails - no answer, no QSO.
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73 Bojan S53DZ |
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I work POTA exclusively 5 watt. Either with my QCX or QMX and I’ve had QSOs from coastal NC into Europe, Alaska, Hawaii, and even into New Zealand. ?Antenna is either a QRPGuys triband vertical or an EFHW.
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Usually my assigned RST is two units below what I send back. But I’ve had dozens of RSTs at 117 or so,
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QRP is all about whether the other guy can hear you. ?My POTA station is necessarily compromised, but the responder’s station is not. ?He could be using a mega element beam up 100’ + and max legal power. ?He only needs to be able to hear you and be motivated to answer. ?You can assume that if he answers, he hears you well enough.
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I don’t consider myself under equipped running QRP at a POTA activation. Usually I’m about 10% DX when I activate.
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