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There is a correction to the schematic! I left out the negative feedback resistor and cap on Q1. Corrected schematic here along with same picture of the test fixture from before (which has the feedback). If you saved the previous schematic, throw it away and save this one! Steve AA7U

Here's my latest rig (see pic below). It is a 10 Watt PEP single conversion transceiver using 6 printed circuit boards in a copper clad PCB enclosure. I've been having a lot of fun talking to my friends on 40 meters with this rig. The boards are as follows: 1. VFO board. (purple, front) This uses a raspberry pi pico. The pico has a really inexpensive debug probe you can get for $15. Debuggers make it really easy to find problems with your code. The board has an Si5351 and a 26 MHz 0.5ppm TCXO reference oscillator. I used Platformio IDE to develop the C++ code for this rig. I chose the Arduino framework in Platformio. 2. TX amp and filter board (left wall of enclosure). This board takes the output of the product detector (though a high pass filter) and amplifies it by 40dB. It has 2 stages.: a 2N3904 followed by a 2SC3357. It then filters the output with a triple-tuned bandpass filter for 40 meters. The purpose of the triple tuned bandpass filter is to filter out any spurs from the mixer before they get to the predriver and final amplifier. I thought about relay switching this band pass filter with one used in the front end board, but that would have over-complicated things and maybe introduced some paths to cause oscillation. I wanted to avoid bi-directional amplifiers as I wanted the rig to have AGC. 3. Predriver and final amplifier board (red, rear). This board takes the -9dBm output from the TX amp and filter board and amplifies it to +40dBm (10 Watts PEP). It has 2 stages. A pair of 2SC5706's followed by a pair of RD06HHF1's. If you push it you can get 12 watts PEP out of it, but I don't like running things at their limits. There is only one relay in this rig and it is on this board. The nice thing about push-pull amplifiers is that they attenuate the second harmonic significantly. The 5th order low pass filter on this board is good enough to attenuate all harmonics below the -43dBm limit. 4. Front end and crystal filter. (Green board closest to the rear and close to the pre-driver and final amplifier board). This board has a triple tuned bandpass filter before the mixer and also injects transmit audio into the mixer (which serves as the balanced modulator) during transmit. The output of the mixer is amplified using a 2SC3357 and then put through a 6dB pad before being presented to the 6 pole crystal filter. The crystal filter uses 12.288 MHz crystals. One thing to note about the 2SC3357: You can run it with 40mA of quiescent current, but you need to keep the the Vce below 12 volt absolute maximum in the datasheet. I power all the 2SC3357's in this rig with a switched 9 volt regulated supply. 5. Hycas IF amplifier board with AGC. (Green board closest to the right side of the enclosure). This is a variant of the Hycas IF amplifier featured in QST: https://www.ka7exm.net/hycas/hycas_200712_qst.pdf with some switching modifications to allow adjustable gain on transmit. 6. Product Detector/TX mixer/Audio Amplifier board. (Green board closest to the left front mounted on the bottom of the enclosure). This board contains a mixer, an NE5534 op-amp, and an LM380 audio amplifier.

Gang, I accepted the Soldersmoke DC Receiver Challenge on April 19th. Here is my 3 stage audio amplifier I finished this morning. Please join in on the fun! 73, Alan, N8WQ

Nice piece this morning on NPR regarding Digi-Key. https://www.npr.org/2025/04/24/nx-s1-5332209/digikey-tariff-small-minnesota-town-big-company I didn't know it was started by a ham (AE5E) Jerry KI4IO Warrenton, VA

Looking through my library, this is the earliest example of using PCB pads glued to a board for construction. Is it the earliest you have seen? September 1979 QST (back when there were construction articles) "Quick and Easy Circuit Boards for the Beginner" by Doug DeMaw, W1FB <sk>. Page 30-34 of the "QRP Classics" book by the ARRL dated 1990. FYI -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC DXCC W,VE,JA,PY

Not a direct answer to your question, but ... yes, LTspice can be tough but probably no more than any other true SPICE package. I've presenting an introductory talk on the subject at FDIM. I'm not a super "power user" though. If you have an .asc file that's giving you problems, you can email it to me (include any models not part of the program) and I'll see if I can figure it out. Sometimes a second set of eyes can find a problem. 73 Nick, WA5BDU

I bought a no name LC100a on aliexpress figuring it was worth the risk as they offered free returns. Unless I am really missing something, it looks like I will be taking them up on the free return. I understand my testing method is awful. 5% caps using one cheap device to compare to another cheap device should make most cringe but the Kaiweets meter is usually good. Those are 330pf caps. I have some 1% ones I should dig out but at this point I doubt it will matter. I did run and save all the self calibration routines several times. This is my fault for expecting anything better for $13 from a seller called Pure Pure Grocery Store but sometimes it is fun to roll the dice. Fun fact, the price is already up $5 from 2 weeks ago. Does anyone with one of these devices know of a trick I might be missing or as I suspect is this just more garbage made with floor sweepings?

I've begun building this transmitter (Manhattan style) but cannot get the oscillator to oscillate. Has anyone built this before? I also put the oscillator into LTSpice and did not see oscillation. Does anyone know if this will work?

Steve, AA7U, pointed the following circuit out to me and I just had to build one. Didn't take too long and it seems to work nicely. <https://techlib.com/newprojects.htm> Photo of my build attached. I have some calibration to do to make sure the I_C current is 10mA. You're going to need one of these if the 1,000x2N3904s I'm getting work out. I've checked out 1,000x2N4401s @ 294MHz and I'll give you pointers as soon as the final verdict is in. Less than $20 USD for each batch and the vendor has 50,000,000 in stock, so at $0.01 or so each that is quite an investment in inventory. The f_t above is subject to fine tuning on the fixture is just below the 300MHz min in the spec sheet. This is important as I finalize the ADC-40 transceiver BOM. I found BF245B's for $0.025 each and should have them by the end of the week. With help from DeepSeek, we have results better than what you would get with the 2N3819, MPF102 or J310 jfets. Film at 11. That's end of my budget limit I set, but I have enough for a lifetime. So, get the paypal account ready and I'll help you spend your money, if the measurements pan out. With 2,000+ transistors, I'll not be building anything with an IC in it unless it's in a kit. :-) Looking for others that have checked transistors thoroughly. Open to new and improved ideas. FYI -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,AL MA,OH DXCC W,VE,JA,PY,ZL