[TowerTalk] Homage to Ohmage

[Lux, Jim]

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.