Proven Transmitter Hunting Attenuator



The schematic below or click here version for a pdf is the result of several generations of attenuators that were not suitable for all types of transmitter hunts.  Many of these Version 3 attenuators have been built for hunters in the Denver, Colorado area and they have been shown to work for all types of hunts and power levels.  Some of the features are as follows:

1.) Passive attenuator with loss from 0 to ~45dB with no battery drain.

2.) Combination passive and active attenuator with loss from 10 to ~120dB.  Increasing passive loss before the actiive attenuator keeps spurious signals to a minimum for very strong transmitters.

3.) Use of a balanced modulator (SBL-1) to suppress the fundamental frequency much better than a single diode mixer in active attenuators.

4.) Single control for all types of attenuation.

5.) Current drain of less than 2mA. for long battery life.  The battery can either be 2 AA, 2 AAA, or a 3.6N 1/2 AA lithium battery for hundreds of hours of battery life.

6.) Handles signals in excess of +20dBm.

7.) Usable from 80m thru 70cm.
Click on any pic for higher resolution image
The upper left picture shows the inside construction and the point to point wiring. The small coax is RG-316 and the super small coax is RG-178.  The 2 upper pictures show the attenuator built in a 2.2" x 4.2" x 1.2" diecast box where the lower right has the attenuator built (squeezed) into a 1.4" x 3.5" x 1.1" diecast box and double sided foam taped to the back of a Yaesu VX-5.  The radio can easily be held with one hand and the attenuator knob turned while the other hand is swinging the antenna.
Active/Passive 1 Knob Attenuator V.3
Larry Benko, W0QE    March 2003
Page content last updated Mar. 12, 2008
Copyright 2008 Larry Benko, W0QE

Active/Passive
Attenuator V.3

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