What Is a Valid QSO?

Ham operators make radio contacts on a routine basis. We call another station or another station responds to our call, we exchange some information, maybe chat for a while and then finish the contact, clearing out with our callsigns. Most of the time we clearly know whether we had a valid radio contact, commonly referred to as a QSO.

Sometimes it is not so clear. I hear a DX station calling CQ…I call him (giving his callsign and my callsign) and I hear him say “your report is 5 and 9” so I say “QSL and 73” and put him in the log. Did I really work him? Maybe not. Did he hear my callsign correctly? Was he even talking to me? Not sure.

The question of what constitutes a valid radio contact has been asked for decades. Edward Tilton W1HDQ in the “The World Above 50 Mc” column, QST Magazine, March 1957 wrote this:

As amateurs we are presumed to be engaged in communication. This implies exchange of information, not just identification of one another. Thus, a reasonable definition of a QSO, for amateur purposes, would seem to be an exchange of useful information. Otherwise, why communicate at all?

Tilton goes on to say:

The minimum exchange for two-way work to be considered a contact has been fairly well standardized on a two-stage procedure: positive identification of calls at both ends, and the complete exchange of signal reports. The latter is about the shortest item of information that can be transmitted between two stations that will have any meaning at all. The form varies with various operating activities, but the basic idea of mutual exchange remains in all.

Actually, the exchange of signal reports may be replaced by some other “exchange of information.” For example, during VHF contests the standard exchange of information is usually the 4-character grid locator. Signal reports are not usually given.

The IARU Three Steps

The International Amateur Radio Union (IARU) in their HF Manager’s Handbook and VHF Manager’s Handbook says:

A definition for a valid QSO is:
A valid contact is one where both operators during the contact have
1. mutually identified each other
2. received a report, and
3. received a confirmation of the successful identification and the reception of the report.
It is emphasized that the responsibility always lies with the operator for the integrity of the contact.

Let’s take a practical look at the IARU definition and what it means:

1. mutually identified each other

You exchange callsigns with the other station (making sure you have them correct). This tends to happen naturally as part of the calling process in amateur radio.

2. received a report

You exchange a signal report or some other information (grid locator, contest exchange, …)

3. received a confirmation of the successful identification and the reception of the report.

You acknowledge that you have the information from 1 and 2, by saying “QSL”, “Thank you” or something similar.

Some Scenarios

The rigor applied to making a contact does vary depending on the specific situation. Here are a few specific examples that will help explain this.


The WSJT-X software used for making FT8 contacts has IARU Steps 1, 2, and 3 embedded into its communication protocol. FT8 is intended to work well under weak-signal conditions, so the software implements a rigorous use of information exchange. Appropriate use of this software guarantees a valid QSO.

These are the FT8 messages for K0NR working W1AW.

The QSO starts with one station calling another (callsigns are exchanged). The standard FT8 messages (see figure) show that KØNR calls W1AW with grid locator included (TX1). Typically, W1AW would respond by calling KØNR and providing a signal report. (Signal reports are in decibels, just a number.) KØNR responds with TX3, which does two things: sends “R” to indicate that the signal report from W1AW was received AND sends the signal report of -15 dB to W1AW. When W1AW receives that transmission, it knows that callsigns and signal reports have been exchanged and sends RR73 to complete the QSO. KØNR may respond with a 73 message, but that is not required for a valid QSO.

I realize that if you haven’t worked FT8, this may be confusing. If so, just note that the design of the WSJT-X software leads the user through these specific messages to ensure that the three IARU steps happen.

VHF Contest QSO With Weak Signals

Radio contacts during VHF contests can be a bit casual: one operator calls another (callsigns exchanged) and they tell each other their grid locators. IARU Step 3 (the QSL or acknowledgment) may be assumed or perhaps one of the operators just says thanks or 73 to indicate the contact is complete and they are signing clear. But when the signals are weak, VHF operators tend to be more careful about making sure they made the contact.

Here’s a weak-signal CW QSO between KØNR and W9RM:

KØNR calls W9RM

W9RM responds and sends his grid (DM58)

KØNR responds with multiple “R”s to indicate that the grid was received and sends his grid (DM78)

W9RM responds with multiple “QSL”s to acknowledge that the information is complete

KØNR would probably reply with “73 73 73” but that is not necessary for a valid QSO

HF Contests

HF contests are fast and furious, with a high value placed on quickly making contacts. Thus, they tend to use the bare minimum to complete a QSO. Let’s take the example of a Big Gun station making multiple contacts in succession, otherwise known as “running.” Here, ZF1A is working the CQ Worldwide DX Contest with a number of stations calling him. He initiates the radio contact with “QRZ?”

ZF1A calls QRZ?

KØNR calls ZF1A by just saying his callsign
KØNR: Kilo Zero November Romeo

ZF1A calls KØNR and gives the contest exchange: signal report (always 59 in a contest) and CQ Zone (08 in this example)
ZF1A: KØNR 59 08

KØNR responds with a “Roger” to indicate the information was received and provides a signal report and CQ Zone 04
KØNR: Roger 59 04

ZF1A acknowledges the information and calls for the next station
ZF1A: Thank you, ZF1A QRZ?

This is a fast and tight exchange. Note that to save time, KØNR did not say ZF1A’s callsign during the contact. It does have the potential of a broken QSO if the operators are not paying close attention. KØNR must be sure he is hearing ZF1A’s callsign correctly and that ZF1A sent KØNR’s callsign correctly. Similarly, ZF1A will make sure he has KØNR’s callsign and exchange before moving on. If ZF1A is not sure of KØNR’s callsign and exchange, he will ask for a repeat. Sometimes the running station just calls QRZ? to complete the contact so IARU step 3 is implied. (If ZF1A did not have confidence that the QSO was complete, he would have asked for a repeat.)

Parks On The Air (POTA)

From the POTA rules: “POTA does not require a formal exchange, though many activators will wish to receive real signal reports, names and locations.”  My experience is that the park Activator usually sends a (real) signal report and the park number (e.g., K-4404). The Hunter usually sends a real signal report and state. Something like this:

KØNR: CQ CQ Parks on the air Kilo Zero November Romeo

KØJJW answers him
KØJJW: KØNR this is KØJJW Kilo Zero Juliet Juliet Whiskey

KØNR responds with the signal report and park number
KØNR: KØJJW you are 57 in park K-4404

KØJJW acknowledges the information and provides a signal report and state.
KØJJW: Roger. You are 5 6 into Colorado. Thanks for the activation.

KØNR confirms that the QSO is complete and moves on to the next station
KØNR: QSL and thank you, this is Kilo Zero November Romeo, Parks On The Air

When conditions are marginal, a POTA QSO will naturally tend to have signal reports and QSL messages sent multiple times to make sure that the information gets through.

Summits On The Air (SOTA)

The general SOTA rules state “QSOs must comprise an exchange of callsigns and signal reports, it is strongly recommended that the summit identifier be given during each contact.” SOTA contacts are similar to POTA contacts in terms of format, except the summit number (e.g., W0C/FR-004 ) is exchanged instead of the park number.

Time Constraints

Meteor scatter (MS) is an interesting case, mostly because it can take a long time to complete the QSO.  The two stations are transmitting to each other on alternating time windows hoping that a meteor will streak by and leave an ionizing trail so that a radio contact can be made. It is common for an MS QSO to take 30 minutes or longer.

The message sequence is similar to the FT8 example, so I won’t repeat it here. Imagine sitting in front of your computer patiently waiting for the right meteor burst to occur so that 1) callsigns are exchanged 2) signal reports are exchanged and 3) a final acknowledgment occurs. This raises the question of how long is too long to count as a valid QSO? I don’t know of a specific standard but most people would agree that if the three steps occur over several days, it is probably not a valid QSO. It seems like most hams working MS complete their contacts within a few hours, typically less.

One more question: what information do you need to record concerning the QSO? This will also vary depending on the circumstances, but most hams log callsign, signal reports, time (UTC), frequency or band, and mode. Note that Logbook of The World does not store signal reports but does require and store the time of the QSO, along with the band and mode. Another example: when submitting a contest log, the context exchange from both stations must be included (and these are checked against other submitted logs). The point is you need to be thinking about how the QSO information is going to be used and recorded. [Thanks, Bob/WØBV]


The three steps in the IARU definition of a valid QSO can be summarized as: 1) exchange callsigns 2) exchange signal report or other information and 3) confirm that #1 and #2 happened. This still leaves some gray area when it comes to deciding whether a QSO was valid or not. Most of us have had that funny feeling at the end of a marginal contact: should I put this in the log or not? This is where the final IARU advice applies: The responsibility always lies with the operator for the integrity of the contact.

The post What Is a Valid QSO? appeared first on The KØNR Radio Site.

Bob Witte, KØNR, is a regular contributor to AmateurRadio.com and writes from Colorado, USA. Contact him at [email protected].

2 Responses to “What Is a Valid QSO?”

  • Steve VE7SL:

    Good discussion Bob as there are still many out there that don’t fully understand the minimum criteria. In most of these scenarios I find that without a further acknowledgements of your ‘RRR’ or equivalent, that one party or the other is always left wondering if the contact is indeed complete. I know back in the CW MS days I’d always send my ‘RR73’ over and over just for insurance. It’s similar on FT8 with the choice of RR or RR73 and can often lead to one or the other wondering if it’s all wrapped up. So your final comment is right on the money.

    Real-time internet chat between the same two stations is another topic altogether! 73 Steve

  • Bill Mader:

    In a serious contest operation, the running (calling CQ) op will acknowledge the search and pounce (S&P) op’s report with “thanks” or “TU” on CW. If there were additional callers, the “TU” will suffice and one or more callers will send ONLY their callsigns ONCE. Serious contesters rarely send QRZ. A simple “again” ONCE suffices or “?” on CW. Brevity is the key to good communications and high contest rates. Nobody needs to send “please copy” as (duh) that’s expected. 73, Bill, K8TE

    P.S. These concepts apply to chasing DX, contesting, and working special event stations. As W6H last month, I could have worked more than the 6,700+ contacts I made if more ops used these and Bob’s techniques.

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