Our amateur 1420 MHz radio telescope consists of:



Stacked Yagi with 22.5 dBi gain.  Comprises two 45-element model 2145LY loop Yagis by Directive Systems.  This array was previously used by Dr. John D. Bernard of the Jupiter Space Station Group to observe Hydrogen-line emissions during the comet Tempel 1 collision with the JPL/NASA/UMD Deep Impactor on July 4, 2005.  The antenna stack is mounted on a Yaesu G-550 elevation rotor.



The antenna phasing network is followed by a low-noise amplifier (LNA) for the 1.3 to 1.7 GHz “Water-Hole” band.  This LNA is based upon a SETI League design.  It has a gain of ~21dB.


Coax Cable, Bias T, Filter and Signal Splitter

The LNA is connected to the station’s indoor setup via 50’ of coax cable.  Power for the LNA is supplied via the coax cable by a Bias T.  The signal is then filtered using a 4-pole interdigital filter by Radio Astronomy Supplies.  The output of the filter is split using a hybrid signal combiner/splitter.


Spectrum Analyzer/Receiver:

Hydrogen-line signals at 1420 MHz are down-converted to the 2-meter (144 MHz) band.  The downconverter is based on the design by the SETI League.  NF is 1.85 dB and conversion gain is 49 dB. This converter includes a filter which yields over 50 dB image rejection and 30 dB spurious rejection.  144MHz signals are then received by a home-made spectrum analyzer.


Main Receiver:

1420MHz signals from the second splitter output are amplified using a 28dB LNA kindly loaned to us by Dr. John D. Bernard of the Jupiter Space Station Group.  Signals are received using an ICOM IC-R7000 modified to disable AGC and enable constant operation.  (CLICK HERE for detailed instructions on modifying the IC-R7000).  Audio from the IC-R7000 is fed to the sound card input of a PC.



RadioEyes by Radio Sky Publishing is a great sky viewing software for radio astronomy. Radio Eyes is not just a sky viewer that has mappings for radio objects. It is a tool to help plan radio observations. Radio-SkyPipe from the same publisher can be used to log data in a format that can be used by RadioEyes for display.


Our favorite signal acquisition and analysis software is SetiFox available from its creator, Daniel B. Fox.


Auxiliary Equipment:

Narrow-band signals can also be received by feeding the IC-R7000’s IF to an ICOM IC-R71.  A broad spectral view of the band is obtained by analyzing the IC-R7000’s IF using an Atlantic Electronics SM-7071 panoramic display.


A remotely-controlled 1420 MHz weak-signal source is used as a check source for the station.

Amateur Radio Astronomy

Our 1420 MHz Atomic-Hydrogen Radio Telescope

          This is our receiver setup.  Our main VHF/UHF receiver is an  ICOM IC-R7000.  It features  all-mode (AM/FM/WFM/SSB) reception between 25Mhz and 2GHz.  This receiver is great for general-purpose “scanning” as well as for hydrogen-line radio-astronomy.   An ICOM IC-R71A receives <10kHz to 30MHz (it’s specified 100kHz to 30MHz, but can be easily tricked into going all the way down to a few kHz.  It’s great to receive subcarriers from the R7000).  An Atlantic Electronics model SM-7071 “pan-adaptor” spectrum analyzer completes our setup.  The SM-7071 acts as a spectrum analyzer within the IF of either the IC-R7000 or the IC-R71A.

  This is our station’s indoors front-end.  The chassis encloses the bias-T, Radio Astronomy Supplies 4-pole interdigital filter, power divider, RF amplifier and 1420 MHz to 144 MHz downconverter.

  This is our Stacked Yagi with 22.5 dBi gain.  Comprises two 45-element model 2145LY loop Yagis by Directive Systems.  (Pictured at its prior location  - the Jupiter Space Station Radio Observatory ).

  This is our home-made spectrum analyzer.  It is used to receive and display signals that have been downconverted to 144MHz.

© 2005 David Prutchi.  All rights reserved.

First Light:  October 2, 2005

  We set up the antenna array on its temporary mount to observe solar transit.  At 10am we directed the antenna towards the point at which the Sun would be at 1:30pm.

  We set up “SetiFox” to scan, and then waited very patiently for the Sun to drift into the antenna’s field-of-view.

  The antenna stack is mounted on a Yaesu G-550 elevation rotor.  An electronic clinometer sensor (left weatherproof enclosure) reports the antenna’s true elevation. The LNA is mounted inside the weatherproof enclosure at the right.  It is connected directly to the antenna combiner.


Click Here for more information

Peak of integrated power (1420.2—1420.7 MHz) at time of solar transit

Shanni’s Extra Terrestrial QSLs

Circular Yagi stack for 1420 MHz hydrogen-line observational radio astronomy. www.prutchi.com


CLICK HERE for charts [600kB pdf]

SETI is real science.  We don’t investigate UFO sightings or alien abductions.  SETI astronomers search for scientific evidence of extraterrestrial intelligence.  No verifiable alien signals have been detected so far.

Solar Transit and Galactic Core, November 2005. 

 SETI SuperStar Award

February ’06

CLICK HERE for a reprint of Shanni’s paper presented [PDF] at the 2006 Annual Meeting of the Society of Amateur Radio Astronomers:


Shanni R. Prutchi, “Hydrogen-Line Radio-Astronomy as an Elementary-School Science Project”, Proc. 25th Annual Meeting of SARA, National Radio Astronomy Observatory, Green Bank, West Virginia, June 18 through June 21, 2006, pp. 92-101.