90671 Standing Wave Ratio Bridge

More of a collectors item than a used instrument today! The Millen 90671 was essentially the guts of todays modern SWR meter. The user would supply power to the input of the bridge with the antenna connected to the output connector. A standard 0-1 mA meter is then connected to the two plug-in jacks on the front side of the unit. The meter would be adjusted to full scale by adjusting the RF source level with no antenna load connected. The user would then connect the antenna coax cable to the output and see the resultant meter reading change. The manual provided graphs to determine the actual SWR based on the current measured with the antenna load connected. As delivered it was designed for standard 52 ohm coaxial line, but a 75 ohm resistor was included inside the case to swap out with an internal resistance standard. Thus, it was capable of performing VSWR measurements on both 52 (50) ohm and 75 ohm antenna systems.

I bought the above from an estate auction and it came with the nice wood cabinet shown in the pictures. I'm not sure if this was a Millen option or not. If it wasn't someone sure did a wonderful job building a case just for this bridge. Millen did not supply the actual 0-1 Ma meter. I'm not sure why they didn't, because there are many products made by Millen that have Millen logos on the meters.

Owner: Don Buska, N9OO


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