PSR B0818 - 41 is one of the few pulsars which show multiple drift regions having well defined phase relationship .
In this paper we report new results from the multifrequency observations of this pulsar with the Giant Metrewave Radio Telescope ( GMRT ) .
We determine the mean flux of the pulsar at multiple frequencies and find evidence for a low frequency turn-over in its spectrum .
Significant linear polarization is observed with depolarization at the edge of the profile , which is likely to be due to orthogonal polarization mode jumps .
Circular polarization changes sign near the middle of the pulse profile at 1060 MHz which is not observed at 325 and 610 MHz .
Remarkable frequency evolution of polarization angle ( PA ) is observed for this pulsar , which is commonly not seen in other pulsars .
Based on the frequency evolution of average profile , observed PA swing and results from subpulse drifting , we propose two possible emission geometries , \alpha \sim 11° , \beta \sim - 5.4°and \alpha \sim 175.4° , \beta \sim - 6.9° .
Simulation of the pulsar radiation pattern with both these geometries reproduces the observed features in the drift pattern quite well .
In addition to the remarkable subpulse drifting observed at 325 MHz , we report subpulse drifting at 244 and 610 MHz .
At 244 MHz we observe drifting in the outer regions but not in the inner region whereas at 610 MHz subpulse drift is observed in both inner and outer regions .
Sometimes , we see changes of drift rates , transitions from negative to stationary and stationary to negative drift rates , many of which appear to have some connection with nulls .
We determine P _ { 3 } ^ { m } ( the measured time interval between the recurrence of successive drift bands at a given pulse longitude ) , P _ { 2 } ^ { m } ( the measured longitude separation between two adjacent drift bands ) and \Delta \Phi ( subpulse width ) values at different frequencies for both inner and outer drift regions .
Though P _ { 3 } ^ { m } is the same for all the drift regions , P _ { 2 } ^ { m } and \Delta \Phi values are different .
The peak emission from the leading and the trailing outer regions are offset by \sim 9 P _ { 1 } .
Utilising this information , we solve the aliasing problem and argue that drifting is first order aliased with corresponding carousel rotation period P _ { 4 } \sim 10 s , which makes it the fastest known carousel .
The drift pattern from the two rings are phase locked for PSR B0818 - 41 .
The same is found to be true for , all pulsars showing drifting in multiple rings of emission .
This finding puts constraints on the theoretical models of pulsar emission mechanism and , favors a pan magnetospeheric radiation mechanism .