Pulsar reception with a single 23 element yagi
Of course not everybody has
enough space for setting up a dish antenna. I wanted to demonstrate
that pulsar reception is even possible with a single longyagi and a
good preamplifier. My 3m dish has a gain of roughly 20dBi, or a bit
less because of interactions within the multiband feed system. Based on
the experience that I can detect B0329+54 on every attempt on 420 MHz
with the 3m dish, I decided to build a 23 element yagi following the
DG7YBN design. NEC simulation showed a gain of 18.6dBi, that means a
dish equivalent of 2.6m with 50% efficiency. Also backlobe and sidelobe
suppression is good.
As I wanted to keep the building process as simple as
possible, and additionally have the possibility to assemble and
disassemble the whole system within short time for tests at sites with
low RFI, the boom and the pole and also the tripod are made out of
wood. I can split up the 5.3m long boom into three parts, for easier
transportation inside a car.
Tracking is done manually, using a very simple indication system, similar to my first 5m dish for EME back in 1982!
23 element DG7YBN yagi
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Elevation adjustable in steps of 5 deg, good enough as the 3 dB beamwidth of the antenna is 23 deg.
But now I have drilled more holes to have 2.5 deg steps.
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Azimut indication and adjustment is also done in a simple way.
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Observations
were made on 429 MHz using this antenna, 2-stage preamplifier up
at the driven element, 4-pole interdigital filter followed by a
RTL-SDR (2MHz
bandwidth). For using 10 MHz bandwidth it would be necessary to go down
to 420 MHz in my case, because of the RFI situation. I did not measure
the performance of the yagi on that frequency yet, probably it is worse
than with a dish which is more broadband.
Also the intention was to have a system which is cheap, and easy to build and set up, to encourage others to try themselves.
See
below the results of a 4 hours observation of B0329+54
2 MHz bandwidth,
software IW5BHY
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2
MHz bandwidth, software Presto
The quality of the reception is roughly the same as with my 3m dish!
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