Thursday, January 19, 2012

Baofeng UV-3R: Fix for Extremely Low Power

Many hams have measured the output of the UV-3R on low power and noted that is extremely low - as low as 100 mW. SP3SWJ reports a fix by "exchange some inductance in first stage transistor driver from 47nH to 220nH." You see his notations in the schematic here. He also reports the change improves the spurious transmissions on the harmonic.

Here are his measurements using Motorola R2670 on SMA antenna port:

HI POWER +33 dBm
2nd harmonics -27 dB
3rd harmonics -41 dB

LO POWER +16 dBm --- before fix
2nd harmonics -10 dB
3rd harmonics -44 dB

LO POWER +31.4 dBm --- after fix
2nd harmonics -27 dB
3rd harmonics -47 dB

He says the the change improves the output across all VHF frequencies.

Bert, DD5XL, verified that the mod works:

He "used a 150nH wire-wound 0603 SMT coil to replace the stock 47nH type. Before that my low-power output was around 60mW, it increased by nearly 10dB now up to 620mW with a fully charged battery (4,1V). High output is at 2,1W now, this increased of about 200mW compared with before mod.
I've also made a quick check with the spectrum analysator for the low-power setting, the first harmonic is now down to roughly -45dB, this is also an improvement although I already had a improved harmonic suppression by the PA0EJW filter mod."

Via the UV-3R Yahoo Group

No comments:

Post a Comment