(25) THD(%)

[SlideRule]

An extract from Making Distortion Measurements with a Spectrum Analyzer, Broadcast Engineering, JAN 1978, pgs. 78-79

" In reference to … article on AM Proof-of-Performance measurements [June 1977). I'd like to take exception to the statement " there is presently no acceptable way to conduct an official proof-of performance with a spectrum analyzer … ".
  I'd like to discuss my favorite method. because it is much simpler and faster. It relies on the use of a programmable pocket calculator, such as the HP25. The calculator is programmed to solve the equation for THD …
…
  The keystroke listing for the HP25 is given in Figure 1. To use the program, follow the steps in Figure 2. (For a new calculation, go to step 2.) … "

BEST!
SlideRule

[C.Ret]

hI?

I get in trouble decyphering the original HP-25 since a fraction of it is masked at the page's boundary !

At least, I figure out what I have made wrong. I was recalling the \( \sum{x} \) instead the the correct \( \sum{x^2}\) register.

Here is a conversion of the code for HP-15C:

Code:

001-42.21.11   f LBL A
002-      16     CHS
003-       2      2
004-       0      0
005-      10      ÷       //  Divide not add here
006-      13     10^x
007-      49      ∑+
008-    45 4     RCL 4    //  R4 is ∑x²   (I was wrong here using R3 which ∑x)
009-      11      √x
010-      26     EEX
011-       2      2
012-      20      ×
013-   43 32   g RTN

To start a new computation, don't forget to press f CLEAR ∑ g RTN
To enter the values in dB you may press R/S or f A as you prefer.

[SlideRule]

HP-25 Code (from source document)

LINE  CODE    Key
01    32        CHS
02    31        ENTER↑
03    20        2
04    00        0
05    71        ÷            divide
06    15 08    g 10^x
07    25        ∑+
08    24 06    RCL 06    ∑x²
09    14 02    √x
10    33        EEX
11    02        2
12    61        ×
13    13 00    GTO 00    13 03 is a typo

BEST!
SlideRule

[C.Ret]

Ah! Thanks.

The HP25 and H15C codes are quite similar.

I still wandering about the extra ENTER^ instruction. Did my code flow without issue because program execution stop numeric entry ?

Did this extra ENTER^ signify that R/S key don't stop numeric entry on the HP-25 ? So that the ENTER key is mandatory to separate the user's entry from the next 20 entry ?