The general purpose of the Marathon is an increasing QRP activity, using of WW-locators and the lowest usable QRP power. For value estimation of so called "reference distance of QSO" both power of self transmitter and other station used also. It is not contest but QRP statistic game only. All QRP operators of the World welcome.
Date and time: April 1 (00.00 UTC) to April 30 (23.59 UTC)  annually.
Only follow modes usable: CW, SSB, DIGI (PSK, MFSK, HELL, Olivia).
All HF bands 10 to 160 m including WARC.
No any exchanges, Marathon is not a contest. Add your WW-locator and power in report only. Participants may use QRP power only 1 to 5 watts output, other station may use any power. Only 1 QSO per each HF band per each day (UTC) may be submitted. Choose the best resulted QSOs itself. The same station may be submitted if the station operate from different WW-locator not depended of band.
Any passive power attenuators or power dividers are forbidden. Only output RF power from active component before antenna (transistor, valve) must be submitted.
Only QSO distance of 500 km or more may be submitted.
Is not acceptable to reduce output power during QSO! Only CQ or called power must be declared. Only WW-locators may be used for distance calculation. For reference distance of QSO unit of measurement used - Luk.
The reference distance of QSO calculation formula:
Z = L / sqrt (P1 x P2)
L - distance, km
P1 and P2 - both stations power, Watts
Z - reference distance of QSO, Luk

Results of each participants are accumulate separately by the bands.
Winners - by each band results.
There is an automatic calculation special form for add submitted QSOs here -
The memory certificates will sent to every participants.
Add your current QSO's before 23.59 UTC of the next day.
Marathon's Referee have a right to check any QSOs data reliability using any possible way
(ask other operators, ask QSL, eQSL, HRDLog.net, LoTW, QRZ.com etc)
Any prize sponsors and donations are welcome.  
For any questions -

Sponsors and donations are welcome!
"Look In the Horizon"
QRP Marathon