[time-nuts] Subject: Re: Don't use cheap cables -- a cautionary tale
Brucekareen at aol.com
Brucekareen at aol.com
Tue Mar 5 23:54:05 UTC 2013
I would like to add to Bob Camp's comment about twisted pair.
In the past I used to provide one-turn resonant loop antennas for AM
broadcasters who needed to monitor signals from their transmitters at studio
facilities in electrically noisy urban buildings. The three-foot diameter
resonant-loops were grounded at the centerpoint and provided low noise
reception, but this was degraded if a coaxial lead-in was used. A workable
solution turned out to be shielded audio cables. These seemed to have a
characteristic impedance of about 150 ohms. At the receiving end we used ferrite
150-ohm balanced to 50-ohm unbalanced transformers. With the balanced
circuit and shielded audio cable, very long runs could be employed with little
noise pickup.
Bruce, KG6OJI
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