03-01-2018, 05:59 AM
(27-10-2017, 07:57 AM)VK2FAK Wrote: Hi All...
Steve.
The question now is, as you have said you managed to find one of the stronger Pulsars, what are your plans for being able to find more. A new antenna looks like the only way to go, Is a large dish the only possible alternative ?
John
Hi John,
Sorry to take so long to reply - but after a couple of months and no responses I stopped looking (I only logged on because I have a question - which will turn up on a separate thread).
As far as looking for more pulsars - that is a long-term target. What I am looking for at the moment is trying to detect a 'glitch' on the Vela pulsar rotation period. AFAIK it would be the first such detection by an amateur radio astronomer. Every 3 years or so, Vela's slow spin-down rate is interrupted by a sudden spin-up - sometimes up to 3 ppm. I take daily spin frequency measurements looking for such a jump. To improve the accuracy of the measurement (reduce the standard deviation) I am currently in the process of expanding the antenna aperture by a factor of 4: i.e., adding 3 more Yagis to make a 4x1 array.
Steve
(27-10-2017, 03:57 PM)VK2FAK Wrote: Hi...
My question really came out of looking at what others were using, and was surprised at the 3D ground plane design. I would never have thought it would provided enough gain to do the job. So antenna's other than big dishes may have there place..
John
Hi John,
The two smallest aperture antennas used by amateur pulsar hunters are Andrea Dell'Immagine's (IW5BHY) 3D corner reflector antenna @ 422 MHz and my 42-element circularly-polarised Yagi @ 436 MHz. Either of those can fit in a small backyard. Vela passes almost overhead for latitudes from NSW to Tasmania and so my long boom Yagi is pointing nearly straight up. Mind you - it is useful to have good neighbours (mine are fascinated by the antenna and keep asking about the latest results). Each of us target the strongest pulsar visible in our respective hemispheres (B0329+54 for the northern hemisphere; B0833-45 [Vela] for the southern hemisphere). Both our antennas are fixed and pointed to the transit track of the respective pulsars. IW5BHY can get away with a linearly-polarised antenna as B0329+54's signal is almost completely unpolarised. However, Vela's signal is almost completely polarised. This is a problem as the polarisation swings almost 90 degrees during the ~2 ms pulse time - hence the use of a circularly-polarised antenna in my case.
The pulsar signals are very weak and with these two small aperture antennas it is necessary integrate over a couple of hours to extract the pulse.
Personally, the thought of seeing the results each day from an object some 900 light years away AND being able to measure a physical property (rotation period) is still exciting even after 7 months of daily observation. To see a 'glitch' would be even more exciting.
Looking for a cosmic QSL bureau...
Steve