The New England QRP club is pleased to announce the continued availability of the simple and inexpensive HF noise bridge kit.
A noise bridge is a device for measuring or comparing impedances on coaxial cables, antennas, components, etc. With appropriate calibration, it allows for the measurement of both scalar and vector (reactive) impedances. A noise bridge contains a wideband noise generator as well as a bridge balancing circuit, and makes use of the station receiver, tuned to the frequency of measurement, as a detector. The bridge is balanced by changing a bridge capacitor and resistor while listening to the receiver for a noise null. Resistance and reactive values can be determined from the variable R and C positions, and may be converted to an SWR or Z value. The noise bridge may lack the precision of a laboratory instrument; however, it has sufficient capability for normal amateur use and can perform many of the measurements of more expensive instruments such as antenna analyzers. In addition, this version is only 1.1" x 2.75" and can easily be built into other projects.
The New England QRP club's Noise Bridge kit is still available. If you'd like one of these handy little puppies, please email Dave Benson at Small Wonders Lab:
References:
(Kindly provided by Matthew, AD5AP)
J. Althouse, "The Noise Bridge," QST, Sep 1992, pp 75-78.
J. Althouse, "Using a Noise Bridge to Measure Coaxial-Cable
Impedance, " QST, May 1991, p 45.
J. Grebenkemper, "Improving and Using R-X Noise Bridges,"
QST, Aug 1989, pp 27-32, 52.
D. Rodman, "Noise Bridge Audio Links," QST, Dec 1988, p 44.
D. Elkins, "Noise Bridge Aids Transmitter Output-Network
Adjustment," QST, Nov 1988, pp 39-40.
J. Belrose, "RX Noise Bridges," QST, May 1988, pp 34-35,39.
D. DeMaw, "A Laboratory-Style RX Noise Bridge," QST, Dec
1987,
pp 32-35.
A. Popodi, "A VHF Noise Bridge," Ham Radio, Jul 1986, pp 10-19.
J. Carr, "Using the Antenna Noise Bridge," Ham Radio,
May 1986,
pp 69-71.
F. Gehrke, "A Precision Noise Bridge," Ham Radio, Mar
1983
pp 50-56.
J. Althouse, "Antenna Tuning with a Noise Bridge," Worldradio,
May 1978, pp 5-6.
L. Anderson, "Antenna Bridge Calculations," Ham Radio,
May 1978,
pp 33-44.
T. Anderson, "Noise Bridge Calculations," Ham Radio, May
1978,
pp 45-47.
R. Hubbs and F. Doting, "Improvements to the R-X Noise
Bridge,"
Ham Radio, Feb 1977, pp 10-20.
A. Weiss, "Noise Bridge," Ham Radio, May 1974, pp 71-72.
G. Pappot, "Noise Bridge for Impedance Measurements,"
Ham Radio, Jan 1973, pp 62-64.
D. Nelson, "The RF Bridge," Ham Radio, Dec 1970, pp 18-21.
R. T. Hart, "The Antenna Noise Bridge," QST, Dec 1967,
pp 39-41.
An extensive list of references can also be found on Chris Trask's web page at:
http://www.primenet.com/~ctrask/nbridge.html