2B2C: Scratchbuilt Dual-band 2 channel QRP CW rig/ Part 2 Receiver PCB
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- เผยแพร่เมื่อ 27 ก.ค. 2021
- '2B2C' is a project to design, build and document in a video series the design and construction of a two band (40 and 20m) crystal locked (channelised) QRP CW transceiver.
The rig is entirely scratch-built, from 'borrowed' designs, circuit elements and ideas. It is a compact, neat pocket rig that will provide more than adequate service as a simple parks and portable rig, but it comes into its own for SOTA where the crystal-locked channels will not be a major impediment to making contacts.
Frequency control is provided by separate dedicated and trimmed 7MHz and 14MHz crystal oscillators with buffers and with a fixed transmit offset.
The receiver is a conventional Direct Conversion design with strong band pass filtering and an SA612 mixer, followed by a dual op amp for audio filtering and gain, and an LM386 for headphone or speaker listening. It has ample gain both in the shack and on a windy summit.
The transmitter duplicates a significant part of the popular QCX and MTR radios using a high speed logic gate as a digital driver, to three BS170 FETs in parallel for a full 5 watts on both bands. Keying for a straight key is done using discrete components.
The receiver draws about 50mA and the transmitter up to 0.8A on key down. Band switching is done with two miniature telecom relays.
Part 1 - Concept
Part 2 - Receiver PCB
Part 3 - Receiver Band Pass Filters
Part 4 - Receiver build & test
Part 5 - Tx PCB, keying, pre-driver, LPFs
Part 6 - Transmitter driver
Part 7 - Transmitter PA and tests
Part 8 - Cabinet, panel, first outing - วิทยาศาสตร์และเทคโนโลยี
interesting deep dive into your design and build process. I'm enjoying this series of videos, Paul. 73 David
Thanks for commenting David, hopefully some SOTA activations with this little pocket transceiver soon.
Good job, Paul! Thanks for sharing!
Thanks, please check out Part 3; we are about half way through the series, Part 4 published this weekend!
Great video! Looking forward to the next part.
Glad you enjoyed it! I've got a few comments on your recent project, will comment on video shortly.
Thanks Paul great video's binged on them both. Look forward to work you on air with it. vk5cz..
Hi Ian, it has been an interesting design challenge, and I have renewed appreciation for the QCX MTR and other compact QRP CW radios which have dealt with and solved all these issues and a whole lot more that my simplified design avoided. 73 VK3HN.
Informative and inspiring 73
Tnx Praveen, 5 more videos on the way!
very nice and interesting Paul.
Good on you Mladen, tnx!
Muy bueno Paul !!, 73.👍👏👏
Cheers!
wow!!
Cool! Watch the other videos on this Playlist, there's nearly 2 hours of radio making to see!
very very nice ...
Thanks, 5 more videos on the way!
Very nice project and video series! Due to your recommendation I also bought the book about transceiver design! Apart from stacking the two PCBs one over the other, wouldn't it also be possible to connect them butt-to-butt with the SMD component sides facing outside to further ease adjustments and repair?
Guten Tag. That's an interesting idea. The resulting problem is that the dual board assembly must then be mounted above the metal case with spacers. The allowance for components is a minimum of 10mm. In my arrangement, the bottom of the two boards presses flat against the aluminum case. This is good for screening and RF stability, and also for heatsinking, although that's not a big issue in this design. The 0.1" headers and mating pins occupy 12 to 13mm and this is just enough to fill in with the lower board's components. It's an interesting design challenge, designing to meet physical, electronic and RF constraints all at once. Auf wiedersehen.
@@Paul_VK3HN Guten Morgen! It's an interesting design challenge, indeed! Considering the spacers: maybe with a groove in the frame, the sandwiched PCBs could be held in place with minimal area loss. Viele Grüße, ich freue mich schon auf die weiteren Teile der Reihe!
Hi Paul. After last weekend's GQRP convention, I've been thinking of moving on from perfboard and etching my PCBs. I like your approach because you seem to bypass using a transfer (I don't have a laser printer) and drilling through holes. Am I correct in assuming that you do a modified Manhattan approach? In other words, you etch by hand and then you surface attach all your components to the copper after tinning each exposed trace? Do I have that right? Thanks for all the videos. They're very helpful for us in the field. Jack, NG2E
Hello Jack, thanks for commenting again. You are correct, that's exactly how I do it. Mark up pads with a 'texta' or 'Sharpie' of felt-tip pen on the bare copper face, etch the unprotected copper away in Ferric Chloride, clean it up and solder the parts direct to the copper. So it is Manhattan style on copper islands, with joining tracks. Video here: th-cam.com/video/-guLpzvVVC4/w-d-xo.html
This is an easy way to work with leaded components or surface mount. I can mark up, etch and commence the assembly of a simple baord in an evening. Having said that, I've just started using EasyEDA and JCLPCB for truly excellent PCBs, with consequences like a lot of extra design time, the one to two week turnaround time and the cost (mainly couriers as it turns out) that need to be considered.
All the best for your projects, once you can make your own PCBs however you like them, you have a wide open field of options. 73 Paul VK3HN.
@@Paul_VK3HN , thank you so much. Yes, I saw your etching videos. Very helpful. But I had wondered about the ruggedness of Manhattan style. I know my SOTA “appliance” gets a little beat up. I handle any scratch built transmitters with kid gloves. Seems your builds-and those of Charlie Morris-hold up just fine for field use.
Do you have antennas in mind when designing this? Is an EFHW with a single trap a good option for this rig?
The rig is 20 and 40m. I'm using an end fed half wave with a simple tuner, by Steve Yates AA5TB. You can see the tuner, and me throwing the wire over a tree, in the first video. 20m of wire is a half wave on 40 and a full wave on 20. The tuner matches both. (There is no trap, just 20m long wire). It will work on 10m as well. Search up Steve's excellent pages for the theory and construction.