- Remove the nut from the rotary encoder.
- Remove the four screws holding the circuit board: There two near the
lower-middle of the board and also two just above the display.
- With the display face-up, there is a solder connection to the SMA connector
near the connector itself on the circuit board. While gently lifting up on the
bottom of the circuit board, apply heat. The center pin of the SMA connector
should easily pop out when the solder is melted. Note that lead-free solder is
used, so you'll have to turn up your temperature-controlled iron to a higher
temperature.
Once the board was removed, I alloyed the lead-free solder in the hole where the
SMA connector was with "leaded" solder and removed it - a process that I did
twice. With old-fashioned leaded solder, the working temperature was lower and
the eutectic mixture was more favorable to working and then I cleaned the hole.
VHF second harmonic
All UV-3R Mk.Is, and some Mk.IIs and UV-X4s up to a certain serial number, emanate a strong
second harmonic at the antenna terminal when in the 2m ham band (145 * 2 = 290 MHz). When
a VHF resonant antenna is connected to the antenna socket the effective radiated power of
the 2nd harmonic
probably
lies within required FCC/CE specs. A fix has been published in the
Yahoo Group Files section and consists in adding a capacitor to the output low pass filter.
UV-3R Mk.IIs and UV-X4s after a certain serial number (see the database) have a reduced 2nd
harmonic compared to Mk.Is and early Mk.IIs.
For owners in the United States of America, stock UV-3R (MarkI and MarkII) are Part 90
approved, not Part 97.
For owners in the European Union, the stock UV-3Rs comes with CE0678 certification (starting
point for further information is
http://ec.europa.eu/enterprise/sectors/rtte/documents/)
.
Loud volume and 1750Hz access tone
Many users are irritated by the volume difference between the ham bands, the FM broadcast
radio, and the various beeps. While the two ham bands and the beeps are already pretty loud at
the minimum volume setting, volume has to be increased for the FM broadcast radio.
There are two possibilities:
1.
increase the AF amp feedback circuit - this reduces the overall amplification and is only
useful when the FM broadcast radio volume is less important. This mod is described
in detail at <TBC>. R15 (100k) is decreased down to at least 33k, to provide stronger
feedback and hence less total amplification (a 27k soldered across R15 brings the total
resistance to 22k).
2.
modify the balance of the audio being mixed, by reducing both the levels of the ham
bands path and the beep audio path. For the ham bands path R13 (10k) may be
UV-3R FAQ v. 2012-01-27
Page 25
