Cruise through the lower part of the ham bands bands and what do you hear? Well, FT-8 and CW.
Often you will not hear any SSB stations yet go to the lower part of the bands, and it is a cacophony (I love that word) of bad sounding signals and some high-speed keying. Fast is not so much of the issue as is bad, run together and jerky keying. But none the less our hobby started there.
So, you could crank down your ICOM 7300 and watch the waterfall on CW or you could homebrew a radio. Actually, to do CW right you need more thought up front than you do with a SSB transceiver. Often, I will state that a CW Transceiver is much more difficult to build than a simple SSB rig. I published two articles in QRP Quarterly on CW transceivers and all I got was a yawn so maybe history will repeat itself. Yawn!
Of interest is that the LO is a Varactor tuned LC oscillator using a NE602. Look closely at the RIT circuit which is only activated on Receive. But I also used something from the 17M SSB transceiver built in 2007. This is a heterodyne VFO where for 30M a 12.96 MHz Crystal is the injection frequency and data is provided for use on 40M. A broad band RF amp stage provides a bit of a boost after the NE602. (In one similar CW rig I used the AG303-86G MMIC for the boost.)
If you haven't guessed already the IF is 5 MHz where you might get a bonus of WWV on time all the time in your rig if you do not pay attention to unwanted coupling. The other key point: the LC VFO is operating in the 2 to 2.5 MHz range thus the drift is minimized, and the range is limited so it gives slow tuning. Yes, once again N6QW on the leading edge.
I should mention that this 30M radio was not my idea. I was approached by one of the QQ Editors to create a 30M CW Transceiver as he thought I had built enough SSB radios that were published in QQ. So, I did it. But I did not know how to do the RIT and that info was supplied by the QQ Editor.
The IF block and the CW Generator trace their roots to my famous KWM-4 SSB/CW Transceiver where the generated CW was keyed in a buffer stage and injected into the 1st IF amp stage bypassing the Crystal Filter. In normal operation the offset is from a 2nd crystal oscillator that is about 700 Hz off from the receive BFO (5 MHz)
Above shows the TUF-1 Rx Tx Mixer & BPF. The BPF used a pair of those Green Core 10.7 MHz IF transformers back-to-back coupled with 4.7pF Cap and peaked for 30M. How cool is that?
Rounding back to one of the 1st comments about a CW transceiver being complex. There are some innovative circuits in this rig including the LO, how CW is generated and the whole topology, but this adds parts and complexity.
Bi-directional RF stage
I was successful in the build and made one contact for proof of concept and then rebuilt the radio into a SSB Transceiver. For me the 30M CW was a pet project of my QQ Editor and wouldn't be my 1st choice. This that is why you see the 40M data. This was a bespoke project and is not the simple radio I was suggesting in the title! A few more pictures.
[BTW this project caused me to get really pissed at QRPARCI and QQ. Several years ago, QQ republished this article without telling me. I only found out because I started getting emails with questions. I wrote the chief editor asking why I hadn't been contacted or advised of the reprint. That so&so said that QQ owned that article and could do what they wanted. Well folks I didn't get paid for the article and I supplied all of the parts and did all of the work and now you say you own it. QQ will never see another of my projects! I have heard from others that the quality of the QQ articles has diminished over the past several years so likely others are pissed at QQ.]
Here is an example of a simpler 40M CW transceiver.
Shudder -- this used an LC VFO at 5 MHz with a three-pole filter at 12 MHz for the IF. The Audio amp is one of those complimentary pair amps that originally had the 2N3904/2N3906 in it and without changing any other components these two were replaced with a TIP31C and a TIP32C -- that upped the output to 1 watt.
The TR Switch was a Double Pole Double Throw Switch soldered to a PC Board. It did have an Rx RF Amp (2N2219A). The transmitter was a 1-watt Crystal Controlled unit on 7.030 MHz as the source frequency. (I think this came from the 30M CW Transceiver where the 2nd 2N3904 was replaced with a 2N5109.) I had a functionality to drive an external amp for about 80 watts into the antenna. The keying was softened (PNP Keyer) and sounded OK. The Product Detector was a BF991, Dual Gate MOSFET.
I threw this together for a presentation to the Long Island CW Club. About a week before the presentation, I shared the info with the club contact -- Surprise -- he said we don't want that -- we want to see your homebrew SDR rig used on CW using QUISK! You never know and that is what I did.
But all was not lost, as having a crystal filter this simple CW Transceiver was starter sourdough for another SSB transceiver.
You could follow this with a 2N5109 and easily get 1 watt to the antenna. Use the W3NQN filters on the output.
A PNP RF Amp stage good for 10dB gain
Some ideas to ponder regarding making a simple CW transceiver -- you are a month away from March Madness so there is time! Get off the couch you couch potato and heat up the iron!
73's
Pete N6QW
PS The Magic Decoder Ring worked yesterday on one of the Seeed Xiao RP2040 problems -- it will now talk to me.