An answer on Basic QSO format? mentions things like "QRM" and "QSB". What do those terms mean?


5 Answers 5


"QRM" is one of many Q-codes used as abbreviations in radio communication. "QRM" in particular refers to human-generated interference (as opposed to "QRN" which is used to refer to atmospheric noise). "QSB" refers to fading (variation in signal strength over time).

The codes originated from the desire to keep CW (morse code) transmissions as brief as possible due to the format's inherent bandwidth limits, but have stuck around and now often show up as abbreviations in regular conversation as well.

  • $\begingroup$ yeah, sorry; should've been clearer in my answer. $\endgroup$
    – scruss
    Oct 23, 2013 at 2:19
  • 2
    $\begingroup$ No worries. I think there's a general tendency in the ham community to tend towards jargon; I just like to help make stuff more approachable for people who aren't as familiar with the lay of the land. $\endgroup$
    – Amber
    Oct 23, 2013 at 5:51

I keep these "Q" signals in line with this :

  • QRN is "N"atural band noise ( lightning )
  • QRM is "M"an-made band noise ( crowded signals )
  • QSB is "B"utterfly effect from Ionosphere in-stability.

QRM is interference in general, regardless of the source, mostly because it's rarely obvious what the source is. QRN is static, like with wall switches and atmospheric noise. Not sure where / when the "man-made" and "nature-made" thing came about, but I don't believe they are generally understood meanings of those Q-codes.

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    $\begingroup$ The QRM and QRN Q codes are over 100 years old. Back in 1912 the noise from modern electronics was non-existent; received noise was either "atmospherics" (natural noise, or QRN in other words), or obvious interference from someone else's signal or harmonics, i.e. QRM. Nowadays most people would agree with you that QRN means static-like noise regardless of the source, but some people operating far away from civilization can probably still distinguish the difference between QRM and QRN, similar to the way that they see many more stars than city folks. $\endgroup$
    – rclocher3
    Feb 4 at 0:00

To clarify some of the definitions of QRM here:

QRM is a signal from another radio station, that is interfering with you hearing the station that you are in QSO with (or you want to receive).

  • It can be any mode: CW, SSB, AM, digital, etc.
  • It can be another amateur station
  • It can be a shortwave broadcast station.
  • It can be a jamming station run by a country.

QRN is lightning, power line arcs, or similar RFI.

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    $\begingroup$ "signal carrying intelligence " Someone tuning their rig is QRM, but does not carry intelligence. $\endgroup$
    – Duston
    Feb 4 at 14:14
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    $\begingroup$ The ITU standard is specific to "being interfered with", yes. But common use, especially among Amateurs (a service where some of the ITU Q codes make no sense anyway) has drifted from the meanings set out in the 1920s. As a specialized language it has evolved as languages do. Few Amateurs would consider this definition to be much more than pedantry (even if that pedantry was for fun in an on-air conversation). $\endgroup$
    – user21417
    Feb 4 at 14:16
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    $\begingroup$ Similarly, QRN is broadly speaking about being "troubled by static" (as defined and observed in all services). It, too, has drifted into the common use we see/hear today $\endgroup$
    – user21417
    Feb 4 at 14:19
  • $\begingroup$ @MikeWaters, I don't believe "QRM" is used that way any more. Today, it's any kind of interference, intelligent or otherwise. $\endgroup$
    – Noji
    May 15 at 19:17
  • $\begingroup$ @Duston Thank you. Removed that from my answer. $\endgroup$
    – Mike Waters
    May 15 at 23:02

I may have introduced a new Q code, it is used locally and often. QRM - (Man) made, such as electrical, cross talk, etc QRN - (natural), lighting QRW - (wife) occurs when husband spends excessive time on the air

  • $\begingroup$ While this is cute, it's not really a useful answer to the question. :) $\endgroup$
    – David Hoelzer
    Sep 22 at 19:15

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