On 10/21/21 1:52 PM, KD7JYK DM09 wrote:
Exactly, its off by 2 ohms! Supposed to be 50. LOL!
When we had standards, it was 52. Once standard became "nominal", it
was rounded down in print to cover sloppiness/ease in manufacturing.
I don't know that 52 ohms was ever a "standard" - Just today, I was
sorting through a lab here at JPL and a pile of loads and pads from the
early 60s (yes, labeled in KMC), many with their original careful
calibrations (that's not just a 10dB attenuator, it's a 10.22 +/- 0.01
dB attenuator)
They're all labeled 50 ohms.
And picking up one and measuring it with my not recently calibrated
(2014) Fluke 77, they measure 50 ohms +/- 0.1
Long since discontinued MIL-C-17 M17/74-RG213 specifies
Characteristic impedance: 50 ohms +/- 2
FWIW M17/28 (RG-058) says the same thing.
Now, those are modern (from 1977)..
It is true that there are people selling "RG-8 like" coax that they
claim is M17/74-RG213 equivalent, and has nom impedance: 52 ohms, and
nom cap 29.6 pF/ft
https://www.awcwire.com/rg-catalog/rg8-coax-cable
(Their RG-213 is 50 ohms and 30.8 pF/ft)
SO maybe, it was the decadent period of the 70s, when RG-8 was cast to
the side like a soiled tissue (actually, all the RG were ended) and
Mil-C-17 M17/74-RG213 replaced it.
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