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The photos below document some of the hardware development initiatives being pursued in the SETI League laboratories. More details on this and other equipment may be found in the SETI League Technical Manual.
| Dr. Dave Clingerman, W6OAL, through his company Olde Antenna Lab, produces a commercial SETI LNBF assembly (integrated Low Noise preamp, Block downconverter and Feedhorn) for Project Argus use. Here on his workbench, the helical feed (left), LNA (right, smaller box) and downconverter (right, larger box) are awaiting installation into the PVC radome (seen at rear center). |
 W6OAL photo |
| Here the Olde Antenna Lab SETI LNBF (see photo above) is inserted into its radome, and is awaiting sealing and end-caps. The helical antenna feed can be seen at left, just inside the PVC pipe. |
 W6OAL photo |
| Inside and outside views of Hardware Committee chairman Lee Kitchens' Project Argus feed assembly. Lee writes, "aside from the electronics, just about any part can be made or found locally. I couldn't find an airflow fan switch so I made one out of a lever microswitch, paperclip arm, and airflow paddle made from tin sheet. The waterproof containers are Rubbermaid. The waterproof 'Air In' - 'Air Out' are plumbing elbows. Old heat sink. Bought a used Peltier for $25. LED out of an old radio. If the fan fails for any reason, the paddle will fall shutting off power to the fan, Peltier, and LNA. All power wires are shielded. Had to move the 12V power source outside close to the dish because the voltage drop in the power line from the house made the fan's airflow insufficient to move the paddle." |
KB9PIP photos |
| In an innovative approach to bandpass filtering, SETI League member and Eastern Australia regional coordinator Noel C. Welstead has built this coaxial cavity for his station, and finds that inserting it in the feedline between his first and second preamplifier stages decreases radio frequency interference. Watch this space for future documentation of this filter design. |
 VK4AYW photo |
| Tom Clark's Totally Accurate Clock project is providing SETI League members with a low-cost precision time and frequency standard. The circuit board shown here interfaces via an RS-232 connection to a personal computer's serial port. The metal box seen mounted above the circuit board is a Garmin GPS, with its patch antenna on top. In addition to providing accurate position information and both Greenwich Mean Sidereal Time (GMST) and Local Mean Sidereal Time (LMST) to atomic-clock accuracy, the unit can be used to slave a precision crystal oscillator to 1e-09 (one part in a thousand million) accuracy. |
SETI League |
| Executive director Dr. H. Paul Shuch attempts to measure sun noise with a portable radio telescope. This system serves as a test-bed for the hardware and software to be used for the recently initiated Project Argus all-sky survey. The actual antennas used for SETI are much larger. |
SETI League |
| WSS-1296 PC Board, sold by Down East Microwave to produce a test signal in the 23 cm amateur band, was modified by SETI League engineers for use as a 1420 MHz weak signal source. The manufacturer is now offering the modified board and kit as commercial products, under the model number WSS-1420. |
SETI League |
| Stable, low-cost hydrogen-line weak signal source, with a quarter-wave antenna of brass hobby tubing soldered to the output microstripline. The test signal can be heard in sensitive SETI receivers at a distance of several hundred meters. Construction details appear in the accompanying article. |
SETI League |
| The commercial version of the SETI League weak signal source is sold by noted equipment supplier Down East Microwave, as their Model 1420-WSSK for $60 in kit form. Here is a packaged version, using an enclosure supplied by Down East Microwave. (Note the homebrew querter wave whip antenna at upper right.) A discount is offered to SETI League members in good standing. |
SETI League |
| The Down East Microwave 23LNA, a preamp for the 23 cm ham band, is easily modified for SETI at the water-hole by removing one turn of wire from the input inductor (seen here to the left of the FET). In noise figure competition at the October 1997 Microwave Update conference, the modified unit measured in at 14.9 dB gain, 1.02 dB noise figure at the 21 cm hydrogen line. Priced at $50 in kit form, $75 assembled and tested, this easily modified unit is an economical path to superb SETI performance. |
SETI League |
| Swept frequency response of the modified Down East Microwave 23LNA. Initial gain peaked at +17 dB at 1296 MHz, and dropped to +12 dB and +7 dB at the 1420 MHz hydrogen line, and the 1660 MHz hydroxyl line, respectively. After modification, the gain figures at those three frequencies are +13 B, +15 dB, and +12 dB, respectively. Noise figure appears flat at about 1 dB. |
SETI League |
| Swept frequency response of a hydrogen-line AmpliFilter being tested at The SETI League's microwave lab. One of the SETI League's hardware initiatives is the development of standard, frequency-selective gain blocks for use in the next generation of microwave receivers. This AmpliFilter is constructed on an existing weak signal source printed circuit board (the DEM WSS-1296 used in other SETI League projects), with all filter poles shortened by exactly 0.1 inch on each end (12 places total). |
SETI League |
| Surgically modified AmpliFilter printed circuit board. The hobby knife cuts are clearly visible. We used an approxo knife to raise the resonant frequency, because there's nothing exact about the process. |
SETI League |
| By trimming another 0.1" off each end of each filter pole (for 0.2" trim total, 12 places), the resonant frequency of the AmpliFilter goes up to 1540 MHz. This is the local oscillator frequency being contemplated for The SETI League's new-technology receiver initiative, STAR-1. Note that, compared to the prior picture, gain reduces by about 2 dB, but the filter skirt response is unaffected. |
SETI League |
| Executive director Dr. H. Paul Shuch, hard at work in The SETI League's microwave circuit development lab, modifying the above AmpliFilter. |
SETI League |
| Not being content to leave well enough alone, we trim the filter poles by yet another 0.1" (for 0.3" trim total, 12 places), to achieve this frequency response. The AmpliFilter is now nominally resonant at the 1660 MHz hydroxyl line. Gain is down by a total of 4 dB from our original design, and the lower filter skirt is noticeably degraded. Nevertheless, we have a workable hydroxyl line front end, which we expect to incorporate into the STAR-1 prototype. |
SETI League |
| SETI League advisor Dr. Malcolm Raff contemplates the schematic of a proposed new SETI receiver. The project, code-named STAR-1 (for Spectral and Temporal Analysis Receiver), is being spearheaded by executive director Dr. H. Paul Shuch, who met with Raff in San Francisco in February of 1997 to discuss the preliminary design. |
SETI League |
| Improved SETI feedhorn incorporating a scalar choke ring, fully described in the accompanying article. The placement of the choke ring along the waveguide feedhorn can be varied to optimize performance for maximum gain, or minimum noise temperature, as required by the user. The feed can also be readily optimized for dishes with a wide range of focal length to diameter (F/D) ratios. |
SETI League |
Follow this link to Hydrogen Line Downconverter photos.
Follow this link to Hydrogen Line Receiver Development photos.
Click here for lots more pictures.
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