In amateur radio contesting, there is a fundamental difference between when an operator can operate two radios and when they can synchronize their operation in time. It is precisely on this difference that 2BSIQ - Two Bands Synchronized Interleaved QSOs stands. This is a way of working, in which one operator simultaneously conducts two Run frequencies on two different bands and time-translates the individual parts of two QSOs so that only one signal is always on the air.
The concept was developed in detail by José Nunes CT1BOH and presented as a separate contesting technique in 2017. So it's not just about "faster SO2R". The essence is a fixed time link between two QSOs, management of TX and RX moments, work with delays and a protocol to restore synchronization.
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What is 2BSIQ and why was it created?
The name Two Bands Synchronized Interleaved QSOs accurately describes the four basic features of this technique. "Two Bands" means two bands and two radios. "Synchronized" refers to the time synchronization of the individual parts of the QSO. "Interleaved" means that two connections do not run consecutively, but simultaneously, and their individual phases are interleaved. The last part, QSOs, reminds that the goal is not just to monitor the second band, but to actually run two RUN links.
CT1BOH defined 2BSIQ as a complex contesting mode that, using a synchronized protocol, allows interleaving of two radios on two bands. The goal is to dramatically increase the number of QSOs per unit time without creating two simultaneous broadcasting stations.
Basic principle: two bands, two radios, only one TX
The basis is a classic SO2R workplace, i.e. two independent radios with sufficient isolation so that they can work on any combination of two bands without mutual interference. The difference is how the radios are used. If radio 1 transmits on the first band, radio 2 must receive on the second band. When radio 1 is receiving, radio 2 can transmit.
Thus, there is only one TX signal at a time. This is important not only from a technical point of view, but also because of the rules of the SOAB category. 2BSIQ is therefore not an attempt to create two simultaneous broadcast signals. Its goal is to make the most efficient use of the time in which the other radio would be waiting in the classical way of working.
Time is the main variable in 2BSIQ. The operator is not only trying to react faster. It tries to divide the individual parts of two QSOs so that their time intervals overlap as closely as possible.
What does "synchronized" mean?
Common SO2R allows the operator to switch focus between two radios. However, knowing which radio to watch or listen to is not enough in 2BSIQ. The operator must know exactly when the next decisive moment will come. Synchronization therefore works with the length of TX and RX intervals, with the reaction time of the counter station and with the transition between individual QSOs.
Each QSO can be divided into four basic moments: termination of the previous communication and CQ, receiving the call sign, sending the report and receiving the report. In a classic QSO, these moments are performed sequentially. In 2BSIQ, the moments of the two QSOs are shifted so that the TX of one radio takes place during the RX of the other and vice versa.
Therefore, CT1BOH identifies synchronization as the key to high rate. If the time coupling begins to gradually diverge, the advantage of interleaving is lost and the operator must revert to synchronized mode.
Interleaving: how two QSOs fit into the time of one QSO
Let's imagine two connections. In the classic RUN, we first complete the entire QSO on radio 1 and only then start another QSO. So the timeline looks like QSO 1, QSO 2, QSO 3 and so on.
With 2BSIQ, the individual parts of the QSO are translated. For example, Radio 1 may transmit a CQ or termination element, then receive a call sign. At the same time, radio 2 will use its TX interval to send the corresponding part of the second QSO. Subsequently, the situation will reverse. It is important that the two broadcast signals do not overlap.
The ideal result is a situation where two complete QSOs fit approximately in the interval that would normally take one QSO. It does not mean that every pair of connections will be exactly twice as fast. The length of call signs, reports, reactions of counter stations and other delays are variable.
Locked QSO moment pair - basis of 2BSIQ
The most important change in thought occurs when moving from classic block QSO to "locked QSO moment pair". The operator no longer thinks about two completely separate connections. It works with a pair of time bound moments of two QSOs.
In this pair, TX is the dominant element. The length of the transmission determines the basic time frame, and the received part of the second QSO must be placed appropriately within this frame. If the received element is too long, a problem will occur. If it is too short, unused time remains or the need for further correction arises.
That is why 2BSIQ cannot be simplified to "I listen to two radios at once". It is a precise timing of four moments of two QSOs.
Video: what the real 2BSIQ sounds like
With 2BSIQ, the audio preview is perhaps even more illustrative than the diagram. CT1BOH released a recording of CR3OO's operation in which two bands can be heard working. It is advisable to use headphones when listening, because the sound of individual radio stations can be monitored separately.
On the recording, CT1BOH is not listening to its own broadcast. During its own TX, it listens to the second radio, i.e. the station that responds on the second band. The two-minute sample contains 17 QSOs, for an instantaneous rate of 510 QSOs/hr. This figure should be understood as the instantaneous speed of the short section, not as the average rate of the entire contest.
Why TX must be the dominant element
In an ideal QSO pair, the TX time of one radio must create a sufficiently stable frame for the RX time of the other radio. CT1BOH explains this by comparing the rabbit and the tortoise: the shorter element must "lead" on the longer element. If the TX is not the dominant part of the pair, perfect synchronization cannot be maintained.
The practical consequence is fundamental. The operator cannot arbitrarily change the length of the broadcast according to the immediate situation. Any TX extension, repeat or unexpected gap is reflected in the next pair. Therefore, it is important to have well-prepared CW macros and to know exactly their duration.
So in 2BSIQ, speed is not only determined by the number of words per minute. Equally important is the predictability of the length of individual QSO elements.
CW speed, mark length and reaction times
The length of the call sign is very important for synchronization. CR3OO's analysis from CQWW CW 2016 showed that at an assumed speed of 30 WPM, approximately 90% of US call signs fit within the 2.55 seconds required to transmit "TU CR3OO". For non-American call signs, it was 74%. The average length of the analyzed American call sign was 2.044 s and the average length of the other call signs was 2.286 s.
These numbers show why the geographic composition of the pile-up can affect the success of the 2BSIQ. A shorter call sign means less risk of the reception interval extending beyond the planned moment. CW speed is therefore not only a question of maximum readability. It must be set up to support a stable time structure.
What happens when sync breaks
The most common problem is lag. If the opposite station responds late, the operator waits for the end of the TX or has to respond to a repeated call sign. This shifts the next moment and the pair's sync begins to diverge.
At this moment, 2BSIQ uses the operational protocol. The CT1BOH material lists four basic mechanisms: Skip, Shift, Delay and Anticipating. Their purpose is to get the pair of QSOs back into the correct time relationship without the operator having to stop the entire process and start over.
Modern experience with 2BSIQ confirms that timing remains a critical element. During live contesting, stations may appear that immediately repeat their call sign after a short delay, or, on the contrary, stop waiting and go to another frequency.
Four operator actions during one pair
2BSIQ looks like an automated process on paper, but the crucial part is still performed by an operator. The CT1BOH divides one pair into four basic actions: pressing the appropriate button or starting TX, capturing and writing the callsign, waiting for the other radio to complete TX, and moving on to the next QSO pair.
On the first radio, for example, the operator can start CQ with F1. During its TX, it listens to the second radio, captures the callsign and writes it to the log. After the end of the TX of the first radio, it goes into the transition interval and prepares the second radio. It then starts its TX, during which it listens to the first radio.
So it is not a chaotic switching of attention. This is a repetitive sequence that the operator must perform with very little variability.
Video: TO7A and original interleaving
Before 2BSIQ there was an interleaving QSO in the form used by UT5UGR of TO7A. CT1BOH used available videos from CQWW CW 2013 and 2014 to analyze this operation in detail. It was these recordings that allowed him to break down the individual TX and RX intervals down to the timeline level.
The video from 2014 is interesting because it is not just a view of the workplace. This is a real audio recording of the operation, on which you can watch how two QSOs are translated and where the time decay of the synchronization gradually appears.
What equipment is required for 2BSIQ
The hardware base is not necessarily exotic. Two radios, two independent RF signal paths, sufficient isolation between stations, and equipment to ensure proper headphone and PTT switching are required. A contest logger capable of working with two radios and with accurate timing of CW messages is also important.
CR3OO used two in 2016 K3, two amplifiers, bandpass filters, antenna switches and stack match. He provided control Dxlog.net. The audio-box had a simple PTT logic: during TX of radio 1, the headphones set to R2R2, during TX of radio 2 to R1R1, and during RX without TX to R1R2.
Interestingly, CT1BOH lists one computer and two keyboards as a more practical solution. Two computers on the network are a possible configuration, but require additional lock-out hardware to prevent simultaneous transmission.
2BSIQ versus classic SO2R
Klasické SO2R umožňuje počas vysielania na jednom rádiu počúvať druhé rádio, hľadať násobiče alebo pracovať stanice mimo hlavného RUN pásma. Je to mimoriadne efektívna technika, ale QSO na druhom rádiu spravidla nevytvára takú tesnú časovú štruktúru ako 2BSIQ.
With 2BSIQ both radios are used as RUN radios. So the operator does not broadcast on one band and only "hunts" on the other. Own QSOs are taking place on both bands, while their moments are shifted in time.
Analýza CR3OO a CR3E z materiálu CT1BOH odhadla pri porovnaní konkrétnych operácií približne o 35 % viac QSO pre 2BSIQ, o 9 % menej násobičov a približne o 23 % vyšší výsledný počet bodov. Ide však o odhad založený na porovnaní historických operácií, nie o univerzálny koeficient platný pre každý contest a každú stanicu.
Where 2BSIQ comes from
2BSIQ was not created as a completely new concept. It is the result of the gradual development of several contesting techniques. One of the basics was SO2R, then inband operation in the Multi-Single category and finally interleaving QSO used by UT5UGR on TO7A.
In Multi-Single inband operation, the RUN station can transmit on the main frequency and other stations on the same band use the times when the RUN station is receiving. P33W, CR3A and 4O3A significantly increased the number of QSOs in this way. For example, according to the presentation, P33W added 3301 QSOs to the RUN operation via inband stations.
CT1BOH came to 2BSIQ precisely through these experiences. Work with PTT, interlock, timing and reaction times was important.
TO7A: why interleaving alone was not enough
TO7A with UT5UGR was a major step. Interleaving was used for the full 48 hours of CQWW CW 2013 and 2014. The result was a significant increase in the number of QSOs - from about 7000 to about 7900. However, CT1BOH pointed out a fundamental difference between interleaving and truly synchronized interleaving.
In the analyzed section, one suitable QSO interval lasted 12.1 seconds. In 241.5 seconds, one radio could theoretically handle 20 QSOs. TO7A made 24 of them with the help of two radios in the given section, i.e. 20% more. The problem was that this advantage could not be sustained.
Graphical analysis of the timeline showed a gradual breakdown of synchronization. The individual TX and RX intervals moved away from each other, and instead of a regular structure, gaps and shifts were created. It was here that CT1BOH identified a space for a new protocol.
As CT1BOH gradually reached 2BSIQ
Development did not start directly with 2BSIQ. As early as 2000, CT1BOH as KH7R used alternating RUN on two bands and achieved up to five QSOs per minute. However, it was classic band switching, not interleaving. Two keyboards, two microphones and two foot switches were used.
Later, the development of advanced SO2R and Alternate CQ mode followed. However, he only used the free time of the second radio. It did not allow two QSOs to be inserted into the time of one QSO. Experience with Multi-Single inband then showed the role of precise timing and interlock.
The decisive impetus was the question why TO7A does not achieve a much higher number of QSOs than the classic SO2R during interleaving. The analysis of recordings and waterfall subsequently showed that the problem is not the idea of interleaving itself, but insufficient synchronization. CT1BOH therefore introduced locked QSO moments, information about the end of TX, calculation of the optimal length of moments and resynchronization rules.
Training, simulator and real operation
2BSIQ requires training because the operator must learn to perceive two parallel QSOs as one time structure. CT1BOH had limited opportunities to try this mode on air at his home QTH. Therefore, he used two separate Morse Runner simulators.
Before CQWW CW 2015, he spent around 20 hours simulating. He completed 240 five-minute sessions and logged 7,500 QSOs. The average rate was 375 QSO/h, with individual five-minute blocks ranging from 312 to 420 QSO/h. As of 2016, Dxlog.net also included a built-in 2BSIQ simulator.
Simulátor tu nemal nahradiť contest. Jeho význam spočíval v kalibrácii časovania, CW správ a operačného protokolu. Pri technike, kde aj malé oneskorenie môže posunúť ďalší pár QSO, je opakovateľný tréning oveľa užitočnejší než náhodné skúšanie počas contestu.
Can 2BSIQ change the boundaries of SOAB contesting?
In the original 2017 presentation, the question was asked very specifically: can 2BSIQ help break the then SOAB world record? EA8BH's 2000 performance of 18,010,765 points, 7555 QSOs and 817 multipliers served as a benchmark.
Analysis at the time showed that a combination of about 9,500 QSOs and 690 multipliers would add up to about 19.4 million points. 2BSIQ was thus creating a new space: instead of looking for additional multipliers, the operator could focus part of the strategy on dramatically increasing the number of connections.
Since 2017, however, contesting has continued to develop. Aktuálne výsledky CQ WW CW 2025 ukazujú, že EF8R s N6MJ dosiahol v SO HIGH ALL 26 516 025 bodov pri 12 552 QSO. To je podstatne vyššia úroveň než historický rekord, ktorý CT1BOH analyzoval v roku 2017.
Therefore, 2BSIQ cannot be seen only as a historical technique associated with CR3OO. It remains one of the tools that push the boundaries of single-op contesting performance. At the same time, however, the rate itself does not determine the result. It's a combination of QSOs, multipliers, promotion, geographic location, antennas, and the ability to maintain high accuracy for dozens of hours.
About CT1GOD
José Carlos Cardoso Nunes, CT1BOH, is among the long-time CQWW contest operators. According to his own presentation, his contest history dates back to 1989. 2BSIQ material lists 54 participations in CQWW and more than 250,000 QSOs. Over the years he worked from a number of contest stations and QTHs including P40E, KH7R, CR3E and CR3OO.
Jeho prínos k 2BSIQ nespočíva iba v používaní tejto techniky. Dôležitá je predovšetkým snaha rozobrať contesting na merateľné časové intervaly a hľadať príčinu, prečo určitá metóda funguje alebo nefunguje. Prechod od zvukovej nahrávky cez log až po grafickú časovú analýzu TO7A je dobrým príkladom takéhoto technického prístupu.
Summary
2BSIQ is not simply "SO2R on steroids" or just a quick switch between two radios. It is a precisely defined method of contest operation, in which two QSOs are divided into individual TX and RX moments and these moments are then shifted in time. The basis is a pair of radios, two bands, only one transmitting signal and, above all, synchronization.
The hardest part isn't the hardware itself. It is much more difficult to maintain the time structure of the QSO with different long call signs, different reaction times and unpredictable behavior of opposing stations. Therefore, 2BSIQ has its own operational protocol for delays, offsets and resynchronization.
At the same time, the development from SO2R to Multi-Single inband and TO7A interleaving to 2BSIQ shows the typical radio amateur way of technical progress: not a revolution of a single device, but a gradual uncovering of losses in the existing system. CT1BOH identified that interlacing QSOs alone is not enough. It is crucial that the QSO pairs are locked into a common time structure.
That's why it is 2BSIQ interesting even for a radio amateur who will never fight for a world record. It forces you to think about contest operation as a technical system in which CW speed, delay, PTT, audio path, logger, workplace ergonomics and the operator's ability to correctly time each next step are equally important.