BAOFENG LPF MODS BY ANDY G0FTD ------------------------------ After reading KA7OEI's info on the UV3R Yahoo users group I decided to opt for the 33pF mod as Clint reported that on 2m the power output was raised a little whilst providing and extra 10db harmonic reduction. The 47pf mods keeps the power the same on 2m but add about 20db extra harmonic reduction. Since I felt the -42db was enough,coupled with using an untuned antenna at 288Mhz which could potentially add another 10db attenuation, then a harmonic now being a fracton of a milliwatt seemed okay given it's working environment and lack of potential to cause any problems. CONCLUSION ---------- Power output does appear to be raised and certainly brings the rig in spec. Low power settings are a little odd and appear to be reduced ! Oh well, not too bothered anyway as the low power setting in my measurement before the mod seemed low in the first place. So far a quick check reveals no oddities have occured to the 70cm performance. Here's the measurements I took, low power in brackets. 136 = 1.43 (10mW) 140 = 1.72 144 = 1.85 (40mW) 145 = 2.15 (50mW) 146 = 2.15 (60mW) 148 = 2.34 (110mW) 150 = 2.54 152 = 2.75 154 = 2.75 156 = 2.97 158 = 2.97 (670mW) 160 = 2.54 162 = 2.34 164 = 1.96 166 = 1.72 168 = 1.46 170 = 1.22 172 = 0.92 174 = 0.88 (670mW) Below is the text from Clint describing disassembly of the rig. *** Well, I'm glad that what I did was at least reproducible! Figuring that someone else had (or soon would) shown the way to disassemble the UV-3R, I left that portion out of my missive - but at the risk of redundancy, here it is again: - Set down a piece of cloth on the workbench to capture screws and prevent the front panel and display from being scratched. - Remove belt clip - Remove antenna - Remove battery cover and battery - Remove screw on the knob and pull off knob from the rotary encoder. - Remove orange silicone washer from around antenna connector. - Remove the two screws in the battery compartment. Note if they differ from each other and which one went where! - Lift out the rubber flap that covers the DC and Mic/Speaker connection. - Lift the bottom of the radio out of the case very carefully. It should go straight up until it clears the case and at that point the portion with the PTT/alarm/light buttons on the side should clear the case. At this point, slide out the radio chassis from the top hole that has the knob. - Note that the speaker connects with springs to the circuit board. If they are bent noticeably, remember to (gently) straighten them before reassembly. - 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. When testing the LPF mod, I simply dropped the board back in putting in only the top two screws (those being necessary for RF grounding) and I didn't need to resolder each time: The center pin of the SMA made adequate (temporary) connection for the testing without having to completely reassemble the radio each time! * * *