Baofeng UV-3R LPF Modification, redux

This is the second UV-3R I've modified to have better 2nd harmonic suppression. The first worked better.

This one came with an FCC sticker, ostensibly indicating that it didn't need the fix. Unfortunately, it was even worse than mine.


47uF 1206 capacitor
Frequency Before After
144 MHz -15 dBc -36 dBc
148 MHz -24 dBc -40 dBc

FCC Label

Here's the FCC label in the battery case.

FCC Label


Here are screenshots from an HP 8559A spectrum analyzer.

At 144 MHz, 2nd harmonic -15 dBc:

Before, 144 MHz

At 148 MHz, 2nd harmonic -24dBc:

Before, 148 MHz


A 33pF capacitor didn't provide enough harmonic suppression so I went to a 47pF one. I moved up to size 1206 based on what I had on hand and ease of installation. I also mounted the part vertically, following a suggestion from NX6S.

SMT 1206 Capacitor, 47pF


At 144 MHz, 2nd harmonic -36dBc:

After, 144.005 MHz

At 148 MHz, 2nd harmonic -40 dBc:

After, 148.000 MHz

After, on popular frequencies

Here's the 'after' results on some popular frequencies:

At 144.870 MHz, 2nd harmonic -36dBc:

After, 144.870 MHz

At 146.340 MHz, 2nd harmonic -37dBc:

After, 146.340 MHz

At 147.900 MHz, 2nd harmonic -40 dBc:

After, 147.900 MHz

Frequency Test

It's 64 Hz by, according to my GPS-locked frequency counter:

Freqency, 146.52 MHz