2P3 AM Radio Receiver Kit - DIY for Enthusiasts, Built it into a Radio case !

The Tecsun 2P3 Radio Kit is Amazing. I have been scanning Amazon for months, looking for a follow-up to the Elenco AR Radio Kit for my 6YO daughter. Here I have finally found it. Let me start off by saying, I am officially a "radio guy". As a life-long semi-pro musician and an Amateur Radio Extra Class license holder, I have been building tube amps, antennas and radio circuits for well over 35 years. My tube radio collection numbers over 100 pieces. My workbench is full of the nicer Heathkit last-generation test gear, HP and Agilent equipment, and I have prototyped all sorts of SMD RF electronics in the OEM Automotive industry for over 24 years. I have an eye for quality and I'm known for fussiness on detail. OK, credentials established. This kit exceeded all expectations, starting with the documentation. The neatly and securely packed kit comes with a large-format poster. Heavy-gauge paper with a brilliant 4-color 2-sided print job, registered as well as any I have ever seen. The detail includes a large traditional schematic, but enhanced with actual pictures of each component so everything is really easy to identify. The draftsmanship is open and very good, making it easy to read. You can follow it well while reading the included theory of operation. Voltages at key points are given and the whole diagram is split into the traditional AM groupings - input/oscillator/mixer/IF amps/detector/audio output. Really nice and really clear. The rest of the (LARGE) 2-sided poster has all the goodies: exploded views, component placements, bill of material, parts ID, how to solder well, etc., etc. All in fine detail and high-resolution color. This document was clearly someone's labor of love. Best of all, the translations are excellent and only a tiny bit stilted here and there (charming), but written with a clear reverence of the task and a nice sense of history. The parts quality, (it's not built yet), appears fine. The PCB is 2-sided FR-4, (the good stuff) and seems very stable. The housing is a nice throwback to the 1960's, a simple clear design that fits well in the hand. Everything about it says professional and not "toy". I'm really loving this, can you tell? You betcha. I would have given up my Schwinn banana-seat bike for a month to get one of these as a kid! The design is discrete - meaning it has individual transistors and components, all through-hole and no surface-mount items. There is one IC - but it is just the output amplifier, a simple little SIP CD7368, that looks easy to install and will assure clean output, with minimal fuss. The alignment instructions are pretty clear, and don't require fancy test gear, although the novice may have to read through them a couple of times before the idea gets completely clear - this is radio after all and some sense of theory is needed before you can align the 3 stages to receive as well as a factory unit would. All in all I am amazed at the care and trouble someone has taken to put this all together - the documentation poster is truly amazing and makes the project very approachable for young and old radio fans. Did I mention they also include a gift/storage box just the right size for the finished radio, denoting it's "Homebrew" status? Way cool. Schools, ham radio clubs, Scouts, churches - take note: under some friendly direction this is THE kit to get for a group project, and it's not expensive, so everyone can get one. In my opinion this is the deal of the decade and I hope they made a lot of them... because once word gets out on the street, they are going to go fast. I bought 2, because my other daughter, at 3YO, will be wanting one too...even if she has to practice a bit more will the soldering iron before I'll let her tackle it. And there is a good point to make. This kit comes with everything you will need EXCEPT solder. You have to make a choice. If you use lead-free solder (which I recommend, even though it is a touch trickier to handle) make sure you are using a hot enough iron, around 800F. Invest in a decent imported adjustable pencil iron for this kit. The old standard of ~700F works for leaded solder, (cheaper) but there is the cleanup and obvious health concerns to think about. I've been using lead free solder with the kids, and so far so good. 5 Stars, Tecsun, many thanks to you!!! Someone is finally doing it right again! - Dan N8ZJV UPDATE 2015: My daughter did build this kit (with help of course, she's only 6!) and aside from the missing 10k resistors others have mentioned (which, BTW were shipped to me without me asking) it went really well. The coils were pre-tuned almost spot-on, to my surprise, as alignment using an HP digital RF signal generator soon made clear. (I think you can get decent performance without a fancy generator - but if you have one...it's good to know you have it peaked) We were not disappointed. It worked fine after one small issue - the amplifier SIP went in backwards despite being aware of the possibility. My solution was to use a hot-air gun to carefully reflow the back side of the PCB at the SIP leads, while applying gentle pulling pressure from the component side. Despite already having had power applied, the amp chip was not DOA once installed correctly. Nice. My daughter is SO proud of it - and we made pix and video so she can prove that she really did it! She is already asking about the next project! Kudos again to Tecsun for a wonderful kit - much more kit than the price would imply! Slick!

This is the best AM radio kit available today. Packaging, component quality, PCB quality, and final performance of the radio are all excellent. The radio is of moderate to moderate-high difficulty and is best performed by a builder with good soldering skills. A teen with prior experience assembling an electronic kit is ideal. Younger ages can assemble this kit with some adult assistance. Radio reception is very good for all local stations during the day and distant stations at night. Tuning is crowded due to the small size of the tuning knob and the density of stations on the AM band but that is typical of most small AM receivers. The assembly instructions are the most important part of any electronics kit and my personal opinion is the instructions rate 3 out of 5. The instructions are excellent in comparison to other kits available but room for improvement exists. Below is the criterion I used to rate the assembly document: Clarity - 3 out of 5, The information in the assembly instructions could have been better organized. Technical - 3 out of 5, The circuit technical description contains an average quality description of a superheterodyne AM radio. Some minor English language translation issues exist, Step-By-Step Assembly - 0 out of 5. The greatest weakness of the assembly document is the lack of clear step-by-step instructions. Print Quality - 5 out of 5. The print quality of the instructions is excellent. Drawings and schematic diagrams are excellent. Testing and Troubleshooting - 2 out of 5. The documentation contains minimal testing and troubleshooting instructions. One oddity with the assembly is the process for checking the idle current in three places on the PCB, and then using larger or smaller value resistors to bring the idle current within the desired range. When the current is within the desired range, the builder must solder closed some very small jumper pads. The currents to be measured were in the micro-amp range which is very difficult for the typical low-cost DVM to measure. Instead of measuring current, I recommend the manufacturer switch to measuring the voltage on the collector or emitter resistors. That is much easier to do with a low cost DVM and does not require the use of jumper pads. I used the voltage measurement process with good results. The assembly instructions recommend building each radio function block and then testing each one when completed. However the instructions do not indicate which component should be installed. Below is the order I installed the radio components in order to accomplish the goals of the manufacturer: Audio Amplifier EJ1 - Earphone Jack IC1 - Audio Amplifier IC C8 - Electrolytic Capacitor C9 - Polyester Capacitor C10 - Electrolytic Capacitor C11 - Electrolytic Capacitor C12 - Electrolytic Capacitor C13 - Electrolytic Capacitor R14 - Resistor R13 - Resistor R12 - Resistor VR - Variable Resistor (Follow instructions on soldering VR to small PCB, the solder small PCB to large PCB) Battery Holder Test Audio Amplifier Insert batteries. Plug dynamic headphones into EJ1. Touch soldered terminals of VR with your finger and listen for hum and noise. Remove batteries. If you heard noise, proceed to the Detector section below. If you did not hear noise while touching VR, double-check that all components above were installed correctly and all solder joints are good, then repeat the audio test. Detector C14 - Electrolytic Capacitor C15 - Ceramic Capacitor C6 - Ceramic Capacitor C7 - Ceramic Capacitor D1 - Detector Diode R11 - Resistor Shield Cover Test Detector No tests. Proceed to the 2nd IF Amplifier section below. 2nd IF Amplifier T3 - Transformer Q3 - Transistor R10 - Resistor R8 - Resistor R3 - Resistor D4 - Diode D2 - Diode D3 - Diode Test 2nd IF Perform current check indicated in instructions or the alternative test procedure I recommend below: A. Solder the terminals of Jumper Pad C together (Jumper Pad C is indicated in the top PCB layout of Figure 6 in the instruction document). B. Install the batteries and measure the voltage across R10 with a volt meter. C. If the voltage is between 50mV (0.05V) and 100mV (0.1V), remove the batteries and proceed to the 1st IF Amplifier section below. D. If the voltage at R10 is lower than 50mV, remove the batteries then remove R8 from the PCB and replace with a lower value (120K) from the extra resistors supplied in the kit. E. If the voltage at R10 is higher than 100mV, remove the batteries then remove R8 from the PCB and replace with a higher value (220K) from the extra resistors supplied in the kit. F. Repeat B and C. 1st IF Amplifier SFU - Ceramic Filter C5 - Ceramic Capacitor C4 - Electrolytic Capacitor Q2 - Transistor R7 - Resistor R6 - Resistor R5 - Resistor R9 - Resistor T2 - Transformer Test 1st IF Perform current check indicated in instructions or the alternative test procedure I recommend below: A. Solder the terminals of Jumper Pad B together (Jumper Pad B is indicated in the top PCB layout of Figure 6 in the instruction document). B. Install the batteries and measure the voltage across R6 with a volt meter. C. If the voltage is between 0.6V and 1.2V, remove the batteries and proceed to the Local Oscillator/Tuning section below. D. If the voltage at R6 is lower than 0.6V, remove the batteries then remove R5 from the PCB and replace with a lower value (10K) from the extra resistors supplied in the kit. E. If the voltage at R6 is higher than 1.2V, remove the batteries then remove R5 from the PCB and replace with a higher value (22K) from the extra resistors supplied in the kit. F. Repeat B and C. Local Oscillator/Tuning C1 - Ceramic Capacitor C2 - Polyester Capacitor C3 - Ceramic Capacitor C16 - Electrolytic Capacitor T1 - Transformer R4 - Resistor R1 - Resistor R2 - Resistor Q1 - Transistor VC3/VC4 - Variable Capacitor L1/L2 - Antenna Test Local Oscillator/Tuning Perform current check indicated in instructions or the alternative test procedure I recommend below: A. Solder the terminals of Jumper Pad A together (Jumper Pad A is indicated in the top PCB layout of Figure 6 in the instruction document). B. Install the batteries and measure the voltage across R2 with a volt meter. C. If the voltage is between 0.5V and 1.0V, remove the batteries and proceed to the Local Oscillator/Tuning section below. D. If the voltage at R2 is lower than 0.5V, remove the batteries then remove R1 from the PCB and replace with a lower value (100K) from the extra resistors supplied in the kit. E. If the voltage at R2 is higher than 1.0V, remove the batteries then remove R1 from the PCB and replace with a higher value (150K) from the extra resistors supplied in the kit. F. Repeat B and C. Refer to the Figure 7 of the instructions for the following: Install the knobs, L1/L2 antenna mount, and back cover hex standoff. Secure the L1/L2 antenna with two wire ties supplied in the kit. Install the grill cloth and speaker in the speaker grill. Screw the speaker grill to the front case half. Solder the speaker to the PCB. Insert the PCB into the front case half and secure with screws. Insert the front knob faceplate onto the front case half. Insert batteries and power on the radio. You should be able to receive stations and hear them on the speaker and headphones. Install the back cover. Overall this is an excellent AM radio kit. The assembly instructions and testing sections could be better, but they are actually better than most other kits available today.

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 ohms B. 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 ohms C. 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 ohms D. 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 ohms E. 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 ohms The 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.

マニュアルは、分かりやすく、完成して性能が良かったが、半年で選局ができなくなった。部品の品質に問題あり。

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A qualidade do produto é conforme as minhas expectativas.

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