Empire Model NF-315 useful for audio measurements?

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I recently got an Empire NF-315 Noise and Field intensity meter and now I'm wondering if it is of any use for audio. It was designed in 1963, is transistor based, and apparently is some sort of radio receiver used for measuring RFI.
The BW seemingly is 20Hz to 15kHz. The input impedance can be switched to 50, 600 or 100k Ohm (iirc). It weighs a ton since it has the capability of battery operation. Input is BNC and it also has an output for headphones...
If I understand correctly this is an oldschool spectrum analzer, or more like a spectrum meter, no?
Has anyone worked with this instrument or has any additional info? A source for a manual would obviously be very much appreciated.
 

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I finally managed to play around with the thing, and it's an entertaining piece of equipment.
It turned on nicely, and as far as I could figure out the unit was more or less calibrated. I then fed it a 1kHz sinewave from my smartphone and looked at the fundamental and also the harmonics.
Switching from one level to another is a bit sketchy, i suspect that some resistors went out of spec. The headphone thing is also funny, I believe it is the output of some demodulator, it let's you listen to the distortion in a certain way.
Turns out my smartphone has very low distortion and it's mainly 3rd harmonic.

Beside from that it's virtually impossible to find anything online related to the NF-315, so I'd still be grateful for any input on the device and/or manuals, schematics and so on. If anyone wants to see more pics I can upload some.
 
The free download contains a description of the unit that may answer enough of your questions about the unit for you to decide if it is applicable to your audio testing needs without the expense of buying a manual.

The product literature says: "a sensitive audio harmonic wave analyzer" and "Recording and X-Y plotting outputs". Those features suggest it might be useful for measuring the level of harmonic distortion components and doing frequency response tests.
 
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Thanks xmo for your effort! I have seen the ad before and must say that the actual unit looks slightly different from what the ad depicts.
I have also found the manual for the NF-105 which is similar enough to get an idea of what these instruments do, basically it's a primitive spectrum analyzer like I suspected.

The design is quite intuitive, so it's not too hard to figure out how to use it, and as I have written above, I already used it to look at the distortion characteristics of my smartphone's audio output. In principle the unit works fine, the levels are a bit off due to drifty resistors and old caps I suppose. I'd have to replace a whole bunch of parts, so I don't know if I'll make the effort.
 

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