EME, Radio Astronomy, and SETI
... and the Hydrogen Line
|The hydrogen line, 21 centimeter line or HI line, refers to the spectral line created by changes in the energy state of
neutral hydrogen and occurs at a frequency of 1420.40575177 MHz, equivalent to a vacuum wavelength of around 21.1
cm, or 21.10611405413 cm more precisely. This line falls within the radio region of the electromagnetic spectrum and is
used quite extensively in astronomy, since it can penetrate dust clouds that are opaque to visible wavelengths. The
radiation comprising the hydrogen line comes from the transition between the two hyperfine levels of the hydrogen 1s
ground state. You'll need a receiver that receives well at 1.42 GHz, like the Icom IC-R7000
|Some necessary equipment is shown on the pages below.
Since I am building a new station, much of this equipment is for sale as of March 2010.
Please see the bottom of these pages for asking prices, or Contact me if interested.
The "Starfire" is a prototype of my bias-tee or
power inserter. It is a highly regulated constant
voltage source which is variable up to about 24
It may be switched to fixed voltages or operator
variable selection. The fixed position allows a
switch-selectable preset voltage level to
actuate the polarization switch in feedhorns.
Note the two green LEDs embedded in the volt
meter - these illuminate according to whether
you select the 14 or 18 volt polarity Horiz/vert
feedhorn switch ... it's actually a convenient
way to do it.
The Ampmeter monitors overall current draw,
in the event you are powering an LNA or LNB
over the coax from the rear connectors on the
Power and load
the whole system
while the feedline
unchanged in the
ready at the
|This equipment, mostly all prototypes and engineering samples, were a part of the "E-TRACS" program.
E-TRACS: Extraterrestrial Transmitting and Receiving Antenna Communications System
The "Sunfire" is a prototype of a variable gain
preamplifier and signal level meter. It is to be
used ahead of the Starfire to provide further
control of the inserted DC bias voltages and to
control the input RF signal level, either add
gain or attenuate. This is a valuable tool for
calibrating the receiving equipment. Calibration
is standardized by pointing the dish (feedhorn
antenna) directly at the sun and astronomical
noon and setting the input (thermal noise
signal) to some predetermined reference
(calibration) point. The Sunfire also provides
an audible signal to aid in manual dish
alignment. This device was designed to satisfy
the need to maintain maximum signal-to-noise
feed levels to the receiving system, but without
allowing front end overload and intermod.
The meter and
preamp may be
switched in and
out as required,
just like the DC
bias voltage which
is a part of the
The meter lights
and audio gain
may be adjusted
or inhibited as well.
Various photos of the units. Both of these are marked
"Prototype No. 001" and are hand built and contain all the
final engineering mods. The Sunfire's clear decal laminate
is coming unglued from the front panel. That looks fixable.
These units are now available for liquidation. They have
been lightly used, but show the signs of a few rebuilds,
several mods, and the usual lab-bench scuffs and
scrapes. The power supply is 120 VAC input, ground
isolated and provides the 12 VDC power feed for all the
|Both units together, for $300.00
(+ insured shipping via UPS)