Main Features
The receiver is a single-conversion superhet design tuning from
about 20.25-22.5MHz, with a sensitivity of approximately 1mV for a 10dB
signal-to-noise ratio. Only three controls are provided: RF gain, tuning and
audio gain.
All components are mounted directly on a small PC board
measuring only 117 x 102mm, which can either be used "naked" or housed in a
standard low-profile ABS instrument case (140 x 110 x 35mm).
The receiver can be powered from either a 12V battery or a
mains plugpack supply delivering between 15-18V DC. The current drain is
typically between 55-75mA.
There are two audio outputs from the receiver: (1) a line
output suitable for connection to the line-level input of a PC sound card and
(2) a low-impedance output capable of driving external headphones or a small
8W
speaker. Both outputs can be used at the same time.
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Mention the term "radio astronomy" to most people, and they’ll
either look completely blank or visualise huge arrays of steerable dish antennas
– like the one at Narrabri in NSW. Of course, a lot of radio astronomy is done
nowadays using these big arrays or huge ‘valley sized’ antennas like the one at
Aricebo in Puerto Rico. But it’s still possible to do interesting observations
using much simpler antennas and equipment, at "decametric" frequencies (8-30MHz)
in the HF radio band.
The parts for the Jupiter Receiver are all mounted on a double-sided PC board. The top groundplane pattern is necessary to ensure stability.
In fact, a NASA-sponsored project called "Radio Jove" has been
promoting this type of radio astronomy for the last 10 years as a science
project for high-school students and interested hobbyists. Over 1000 simple
receiver kits have been sold, for 20.1MHz reception of noise bursts from the
planet Jupiter, the Sun and other objects in the Milky Way galaxy.
There’s only one problem with the US-designed Radio Jove
receiver as far as Australian students and hobbyists have been concerned: the
receiver kits cost US$155 each plus shipping from the USA, so it will set you
back about A$200 to have one sent over here. This has discouraged more than a
handful of people in Australia from getting into radio astronomy.
To encourage more Australian students and hobbyists to have a
go, SILICON CHIP has developed its own
low-cost receiver project. And that’s the background to the new receiver
described in this article. You’ll find its basic specifications summarised in
the "Main Features" panel but the bottom line is that it’s quite suitable for
basic radio astronomy at decametric frequencies around 21MHz. This makes it fine
for receiving noise bursts from Jupiter, the Sun or other sources in the Milky
Way.
