# ARRL

Members can access, post and reply to the forums below. Before you do, please first read the RULES.

## Serious Error in 2018 ARRL Handbook!

Mar 16th 2018, 16:25

#### AG6RF

Joined: Dec 13th 2000, 00:00
Total Topics: 0
Total Posts: 0
In the 2018 Handbook, on page 11-3, second column, an equation is given for an AM signal with fC carrier and fM modulating signal. It's the sum of three expressions, one for the carrier, one for the upper sideband, and the third for the lower sideband, as explained in the text that follows.

But the sine functions for both sidebands are shown as the same: 2π(fC + fM)

Also, the arguments for the sideband terms are missing time, t.

Csin(2πfCt) + ((C*M)/2)sin((2π(fC + fM)t) + ((C*M)/2)sin((2π(fC - fM)t)

This is a pretty serious error, as this is the fundamental equation for radio. I'm surprised it got in there.
Mar 19th 2018, 09:27

#### W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Thanks! I added this to the errata page for the 2018 Handbook.

http://www.arrl.org/arrl-handbook-reference

Zak Lau W1VT
ARRL Senior Lab Engineer
Mar 19th 2018, 23:00

#### AG6RF

Joined: Dec 13th 2000, 00:00
Total Topics: 0
Total Posts: 0
Great! Thanks.
Apr 28th 2019, 22:16

#### AG6RF

Joined: Dec 13th 2000, 00:00
Total Topics: 0
Total Posts: 0
@W1VT
THERE IS STILL AN ERROR IN THE 2019 HANDBOOK!!!
The sign of the argument of the third component should be negative: (fC-fM), not (fC+fM)

I have a hard time believing that this error is there in the first place. This equation is the FUNDAMENTAL EQUATION OF RADIO.
Please FIX IT! It's not even in the 2019 errata page.

Errors like this bring all the technical details in question.

May 2nd 2019, 13:05

#### W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Chapter 11 - Modulation

The equation on page 11.3 should read

Csin(2πfCt) + ((C*M)/2)sin((2π(fC + fM)t) + ((C*M)/2)sin((2π(fC - fM)t))