small logo SETI League Technical Manual -- Block Diagram

Line Amplifiers for Amateur SETI
Copyright © 1999 by H. Paul Shuch, Ph.D.
Executive Director, The SETI League, Inc.
PO Box 555, Little Ferry NJ 07643
email n6tx @

Need just a little more gain in your hydrogen line receiving system, perhaps to overcome coax losses? Don't waste money on cascading expensive LNAs; a satellite TV line amplifier works great!

Skyvision [phone (800) 500-9275 in the US] has two 20-dB gain blocks in their catalog. Item #02-3000018 (PerfectVision part number PVAMP-1) sells for $24.95, is currently on special at $19.95, and exhibits flat gain from 950 to 2250 MHz. It is intended as an IF gain block for C-band TVRO systems. Part #02-3034005 (SVI part number ILA-20W) is flat from 40 to 2150 MHz, is priced at $29.95, and is sold as an IF gain block for Ku-band DBS systems. Both units have around a 3 dB noise figure at 1420 MHz, and acceptable dynamic range if used after a HEMT hydrogen-line LNA.

These amplifiers have type F female connectors in and out, are quite small, and require 12 to 24 volts of DC fed through the center conductor of the coax, drawing very little current. They also provide the DC back up to the LNA's center pin, which is useful if you are feeding DC up through the coax already -- simply insert these amps into your existing line, with the appropriate coax adapters, and they work. This scheme will require that you use an accessory called a DC Inserter, or Bias Tee, to supply the required DC voltage to the center conductor of your coaxial cable, if your microwave receiver does not supply it.

I just tested both units mentioned above, and can find little difference in performance for our purposes.

Caution: if you cascade too much gain, you'll end up with GPS satellite responses or interference from other out-of-band signals. If a little gain is good, a lot is not necessarily better.

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