Tecsun 2P3 AM Radio Receiver Kit - DIY for Enthusiasts

I've been aware of the 2P3 kit for some time and finally decided to purchase and build one. As a radio amateur & MW DX enthusiast for nearly 50 years, I've built most of the commercially available ham radio kits. The 2P3, although fairly simple in concept, is an exceptionally well designed & executed kit with all high quality parts and materials. The result of the builder's effort is an attractive and very functional traditional pocket radio that I expect will provide years of dependable use & enjoyment. This is not the average beginners/educational/amusement kit. I consider it a serious kit requiring some requisite basic skills and experience to ensure an enjoyable and successful completion without struggle, troubleshooting, and rework. The poster-sized assembly guide although generally well-written, is a little fragmented in content and does not guide the builder with step by step guidance. I suggest careful study before building is undertaken. I found some differences from western circuit board marking conventions such as hash marks to indicate negative lead polarity of electrolytic capacitors. I had to hunt the assembly instruction for bias current values at 3 test points as well as color code guidance for the ferrite bar antenna wires. Assembly is otherwise conventional and as an experienced builder, posed no uncertainty or difficulty.My first task beyond study of the manual was to take inventory of the parts against the bill of materials. All parts were present in my kit. Upon completion of circuit board assembly, bias current readings were within spec without the need for resistor value changes (as described in the manual). Extra resistors of various values are provided to accommodate if needed. The radio immediately functioned quite well from initial power up. The alignment process was simple but I spent considerable time peaking for maximum performance before I was satisfied....just my nature! Build time from unpacking to completion of alignment to my satisfaction was in excess of 6 hours! This included cleaning of flux and careful inspection. There was no rework involved. Final mechanical assembly was intuitive and all parts aligned perfectly.Performance wise, I found sensitivity is quite good. Selectivity is average and as expected for its design but readily aided by the radio's excellent directional nulling ability. Audio quality is excellent, particularly with headphones, and has plenty of power. Consistent with the 2P3's conventional superhet design, the noise floor is nearly non-existent in an RFI-quiet environment. As a result, signal-to-noise ratio is excellent. This combined with full, crystal clear audio may be an eye-opener for those of us used to DSP-based radios that prevail today. As expected, tuning requires some finesse. One caution - AGC action is minimal and the headphone jack receives full speaker drive without any safety attenuation, so caution is advised when listening with headphones.I truly hope Tecsun will keep this great kit available so all can enjoy it. I'm not aware of any serious competing kit radios currently available. Personally, I'd like to build another one. Availability of different colors or cabinet styles would serve as an excellent excuse! Here's hoping for future availability.

A qualidade do produto é conforme as minhas expectativas.

This was a very enjoyable kit to make and the completed unit works well.For those that have a transistor beta (hFE) tester, a voltmeter, some spare resistors, and a breadboard, you might want to make the following changes to the build procedures:Measure hFE of each S9018 transistor and order them from highest to lowest and then assign them to the circuit as follows (my hFE examples in brackets).Q1 - highest hFE (104)Q2 - mid-level hFE (102)Q3 - lowest hFE (97)Note that the provided kit bias resistors seem to assume hFE 100 so you will know to modify the resistors if you measure far off that nominal value (100).Build and test each section as you go - starting from the audio amplifier, then second IF amp./detector (Q3), then first IF amp. (Q2) then the Mixing circuit (Q1).Calculating modified bias resistors:-----------------------------------------A. Calculate R2 Ve = 0.68 (given on schematic) hFE Q1 measured (e.g. 104) Ic = (0.6 + 0.3)/2 = 0.45 mA desired collector current. then R2 = (hFE1 * Ve) / (1 + hFE1) / Ic e.g. R2 = 104 * 0.68 / 105 / 0.45 = 1.50k ohmsB. Calculate R10 Ve = 0.07 volts (given on schematic) hFE Q3 = 97 (measured) Ic = (1.0 + 0.5)/2 = 0.75 mA desired collector current. then R10 = (hFE3 * Ve) / (1 + hFE3) / Ic e.g. R10 = 97 * 0.07 / 98 / 0.75 * 1000 (mA/A) = 92.4 ohmsC. Calculate R8 Vc16 = 1.853 volts (build and measure the diode voltage source from your kit) hFE Q3 = 97 measured Ic = 0.75 mA (same as step B.) then R8 = hFE3 * (Vc16 - 0.8) / Ic R8 = 97 * (1.853 - 0.8) / 0.75 = 136k ohmsD. Calculate R6 Vc15 = 2.78 volts (capacitor voltage given on schematic) Vc2 = 1.6 volts (collector voltage given on schematic) Ic = (0.6+0.3)/2 = 0.45 mA (range given on schematic) then R6 = (Vc15 - Vc2) / Ic R6 = (2.78 - 1.6) / 0.45 = 2.6k ohmsE. Calculate R1 Vc16 = 1.853 volts (build and measure the diode voltage source from your kit) hFE Q1 = 104 measured Ic = 0.45 mA (same as step A.) Vb = 1.3 volts (given on schematic) then R1 = hFE1 * (Vc16 - 1.3) / Ic R1 = 104 * (1.853 - 1.3) / 0.45 = 128k ohmsThe values of R5 and R7 were used unchanged (as they came in the kit) because their calculation is made more difficult by the circuit feedback. My circuit worked well even with hFE of Q2 (102) being slightly off the nominal value of 100.

Well thought out assembly instructions, require good soldering skills for small components

The radio is very easy to build, and works well. For a small pocket radio it really brings in the distant stations well.