Skip to main content

January 12, 2025. A QRP Rig from 15 years ago.

A bit of fun is to revisit projects that are older than 15 years because in that time span technology has quickly moved forward. That same project 15 years later would most likely have less parts and be more capable.


I think the KWM-4 is perhaps the most complex project I ever designed and built. Mind you I did not simply build someone else's project -- this one was all mine. Prior to the KWM-4, I tried my hand building a solid-state version of the Heathkit HW-100. The HW-100 project went so far as to use the Heathkit Filter and Heterodyne Crystals and ditto for the BFO Crystals. It also had the Heathkit S Meter.  In my build I chose to make it a tri-band rig covering 40M, 20M and 15M. Lessons learned on the HW-100 were incorporated in the KWM-4. 


Main Board


Front Panel on Three Bands

This SS HW-100 is well documented and if you follow the link, there are schematics and lots of construction photos which are presented. There is even a clever band pass filter included used solely for the Digital Display/VFO stabilizer which used a PIC16F84. Instead of the always drifty Heathkit VFO's, I modified a Ten Tec PTO from a Triton IV for the LO. How about those Ten Tec knobs?

Take a few minutes to look at the documentation as it reflects more than taking a couple of TIA amps and using those for a homebrew creation. This project was never published in QQ or SPRAT as this was not some sort of rig that could be easily replicated.

Think about it, as the SS HW-100 and KWM-4 took circuits that were employed in Tube Radios which had to be translated to their transistor equivalents. That is a far bigger job than wiring up a couple of TIA amps and showcasing the result.

Now as you look at the rig think about MMIC amplifiers, ADE-1's, a Digital LO/BFO, Color TFT displays and a much smaller footprint.  The final box is 12X12X6 or half a cubic foot.

This is a one-of-a-kind project which I gave to a ham when I moved back to California in 2013. I regret I did that, but when you have to make a sudden move not all can come.

Them that know can make it go.

73's
Pete N6QW


Popular posts from this blog

January 26, 2024. A simple CW Transceiver/Transmitter

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!   30M CW Transceiver with RIT!   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 ...
Read more

August 30, 2024. A PNP 20M SSB Transceiver

Shown below is the Block Diagram for the 20M PNP SSB Transceiver steered in the  Transmit Mode . The components shown in the dotted block are relay steered so that the block module is single pass and amplifies in a single direction. The Block diagram show steered in Transmit.  Essentially the steering process works so that the IF Module input follows the Balanced Modulator on Transmit and then the input side follows the Receive Mixer on Receive. All done with some relays and a bit of RG174U coax. For those who count things in detail, this block diagram is not unlike what was used for the PSSST Transceiver which can be found on my website . Yes, a warmed over P3ST only using PNP devices. TYGNYBNT. 73's Pete N6QW
Read more

March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking.  I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain. Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs.  That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago. 6AM on the Left Coast ~ 20M Easter Sunday! My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies f...
Read more