Friends and colleagues, Bill, N2CQR and Dean, KK4DAS, developed a Direct Conversion Receiver project that was featured in "hackaday" and the subject of a local High School STEM type project.
Actress Terry Moore (now 96) Read about her in Wikipedia
If you have listened to or watched on You Tube the SolderSmoke Podcasts #254 and #255 then you know this has been the subject of a challenge to another podcast group and to the ham community in general. Dean, KK4DAS in January is sponsoring a 4-week Zoom Buildathon to construct the DCR.
W7ZOI Original DCR Circa 1968
The N2CQR/KK4DAS DCR designs builds upon the FOAM concept championed by Farhan, VU2ESE. FOAM is an acronym for the four parts of the DCR: Filter, Oscillator, Amplifier and Mixer. See if you can spot the FOAM pieces in the W7ZOI design? Because Bill and Dean know stuff, if you follow along, you will be able to do stuff.
But I opine that just building the DCR while it adds to your knowledge base and provides a deep sense of satisfaction of becoming an elite member of a small group who actually built a usable receiver -- it is still a receiver, a superb one at that. The real clout of such a project is taking the next step and making it into a CW transceiver.
So how do you take their DCR and make it into a CW transceiver? That is the $64K question. Now mind you the project is to build their design, not your design. The heart of their DCR is a homebrew PTO (you know LC Oscillator). Using only their design makes things a lot more complex and challenging than what may be done with an Arduino and Si5351 using CLK1.
So how do you do that? If you are looking for a drum roll and/or a quick schematic on a back of an envelope from me -- there is none!
The several sub-challenges include the Offset and the Change Over from Receive to Transmit. Along the way is RIT and Sidetone. These could all be done inside of an Arduino sketch -- but no Arduino would be used.
Just think your very own (not store bought or built from a kit) CW transceiver that will produce many FB contacts. BTW before adventuring out in the CW bands, learn how to send good CW. Regrettably many signals being sent today are pure crap with letters run together and terrible spacing!
Sandra Bullock is one of my favorite actresses and one of her movies ends with a bit of a wish for "world peace"!
Indeed, a great thought that as of today is not in clear focus in the foreseeable future. There is just not the appetite around the world to work cooperatively and if anything, it is every man for himself. That was clearly demonstrated here in the USA just a month ago.
Bad decisions any time, any place, and in any venue are difficult if not impossible to undo. There is no reset button for those who make bad decisions!
But a really good decision is to take our hobby back to its core foundation where ham operators would actually build things. There is both the learning aspect and the satisfaction aspect, and the end result is something useful. It doesn't have to be a self-designed SDR transceiver but something as simple as a dipole antenna or perhaps a Stockton Bridge SWR meter. Avoid kits as there is just about zero learning with a kit other than how to unbox a bag of parts.
This Could be a Radio Shack with Dipole Antennas or an Outhouse!
My most recent learning experience was to come up with a fix for an inoperative KWM-2 power switch. Replacement switches are unobtanium and so a substitute was needed.
True I did see how someone else came up with a solution but what I did was not an exact duplicate of that solution and kept some of the original Collins parts (S11 wafer switch).
I now have in work a second switch which uses all new available modern parts that are more robust and more capable than the design from Collins circa 1956. This replaces both S10 and S11. My 1st sojourn with a fix was very satisfying as it works, and I did not have to resort to drilling a hole in the front panel of one of my KWM-2's.
The second version fixes the power switch but with all parts that can be bought new. This will open the power switch solution to those who don't have a junk box like mine. There is another aspect (in line with world peace) and that is my willingness to share what I know so that others can benefit.
Peace (on a world scale)! Them that know can make it go!
With Christmas but 5 days away, my thoughts have turned to homebrewing special dishes traditionally served only at this time of year. Speaking of traditions, we had one at my home when I was growing up.
The tradition was that on my birthday (December 18) the Christmas tree would be decorated followed by a birthday party. For a birthday cake my mom would serve Zuppe Inglese. Literally translated Zuppe Inglese means English Soup -- but it is so much more than that description.
So here is my mother's version of Zuppe Inglese. You start with four layers of white cake. Each layer is liberally soaked in rum and between the layers is vanilla cream pudding. The outside is covered in real whipped cream and topped with Maraschino Cherries. The cake must be made 24 hours in advance of consumption so that the rum flavoring fully permeates the cake.
A variant likely developed to solve a problem. One traditional Italian cookie is known as Biscotti (the root of the word biscuit). Believe it or not but Biscotti is a cake like cookie that is hard. The idea is you dip the Biscotti into a liqueur like Anisette as it is eaten. The variant is you use the Biscotti instead of the cake. With a rum soak and the vanilla cream pudding the Biscotti softens and is edible. Problem Solved!
The Biscotti are typically almond flavored and when used in the Zuppe Inglese are laid on their side and arranged in a square pattern with the ends cut off to compete the square.
One must be liberal yet careful with the amount of Rum used to soak the medium. There must be enough, so it is recognizable but not so much that it is overwhelming. A steady and sure hand (like soldering SMD parts) is requisite.
Homebrewing can be rewardable and fun -- even edible!
Here is wishing you a Happy and Joyous Christmas although with the clown show soon to be in charge it is a sign that the joy is soon to be gone. If you work in government, you may soon be on furlough and thus a good time to think about homebrewing a Direct Conversion Receiver.
Yesterday was my birthday and I suspect Brad Pitt had a much better time celebrating than I did on our shared birthday. But I did buy myself a small cake with the requisite one candle and thanked God for still being alive
That said I did receive birthday wishes from as far away as Bangalore, India, a couple from the UK, one each from Australia and Italy and a bunch from the USA. It was nice to be remembered.
In two weeks, it will be 2025 and three weeks after that, a new administration will be running the United States. There are troubling signs of what the next four years will be like here.
Clearly already there are words of retribution and revenge mixed with individuals in key positions who clearly lack the experience. But you who voted for this option are now stuck with the results. One must ask what have you done?
There are now less than five weeks to buy that new rig from the Far East before the price impacts commence from the new tariffs.
Friend N2CQR posted my KWM-2 Power Switch Fix on an Antique Radio Forum and of course that prompted a posting (possibly from the resident blog police person) that in essence said that is not the way to do it. The blog poster also mentioned something about using relays in the 516F-2 power supply.
In truth, the relay in the power supply is a better solution and now I will show you how that is done. But what the blog poster police person forgot is that to enable the relay in the power supply you still need a working switch in the KWM2 or 2A. So, step #1 fixes the switch and step #2 installs the relay.
The theory of the relay has as its roots in what is called the Motor Start Circuit. If you want to start a 50HP motor, you do not use a toggle switch in line with the motor. But what you do is to use the toggle switch to control the field coil of a 50HP rated contactor (fancy name for a really big relay) where our field coil draws hundreds of milliamps while the contactor pulls in the current for the 50HP motor (read 187 amps single phase at 230VAC). A fancier form is to use two momentary push buttons where one starts the motor and the other stops the motor.
But we will just stick with our simple snap switch. Using the relay dramatically reduces the current draw through the snap switch. Now, as long as you are using the 516F-2 power supply with the relay you could get by with a one-amp snap switch. But if you use the Collins supply without the relay then you risk smoking the 1-amp snap switch.
So, what comprises the Motor Start Circuit?
Essentially the KWM-2 Power Switch is in series with the field coil of the 120VAC relay and the switch and relay coil are connected across the Hot (Black) and Neutral (White) wires in the power supply. The Neutral is subsequently connected to the Power Transformer. With the Relay, the Hot side is further connected to a set of N.O. (Normally Open) contacts on the relay. Engage the KWM-2 power switch and the relay closes feeding 120VAC to the primary of the transformer. Our newly installed Relay should have a contact rating of 10Amps AC at 125 Volts.
Internally the 516F-2 Collins supply must be modified, and this entails a four-lug terminal strip, a place to locate the relay and a bit of internal re-wiring.
START BY DISCONNECTING THE 516F-2 FROM THE POWER MAINS AND ENSURING THE ELECTROLYTIC CAPS ARE FULLY DISCHARGED! SAFETY FIRST!!!!
Any internal wiring must be downstream of the fuse block. Thus, begin the rewire by carefully observing the wire colors on the schematic to the as built actual supply. Next find the two wires (Green White and Gray White) that come from the KWM-2 Power Switch (pins 5 & 7 on the plug) leave the Green White wire intact but disconnect the Gray White which was connected to the power transformer but now goes to a lug (non-ground) on the new Terminal Strip.
Our Gray White wire on the new terminal strip will now connect to one of the pins of the relay field coil. You will need a short piece of wire to make the connection depending on where you locate the relay. Ensure the wire is insulated and can carry 5 amps. The other end from the relay coil is now connected to the White (Neutral) lead. You may need to create an interim tie point to connect from the other side of the relay to the White (Neutral) lead.
A new wire from the Fuse block where the Green White lead is connected is now connected to one of the NO contacts and the other NO contact is now connected to the primary side of the transformer (Black wire on the Transformer) where the Gray White wire was formerly connected.
Check and double check the wiring and read these instructions several hundred times. If you have never done this kind of wiring, you best not undertake the project as you will likely smoke your radio. The alternative for those lacking homebrew genes is to use a surge protector with an On Off switch and use that to turn on the KWM-2.
The operation is simple. Turn the KWM2, to OFF. Plug in the 516F-2 Power Supply to the radio and the main power cable to the 120VAC mains. Turn ON the KWM-2 and you should hear the relay click and the KWM-2 lights will come on.
Them That Know, Can Make It Go!
73's
Pete N6QW
Hopefully Brad Pitt's 30 something girlfriend has something exciting planned to celebrate his special day. As for me I plan on getting myself a cupcake at Albertson's and have some candles left over from birthday's past. Just another day on the hamster wheel.
Things show up on my phone especially when I search through You Tube. One of the recent videos to appear on the screen was "Spy Radios" from WWII.
Generally speaking, we might see these as pretty crude in comparison to what we have today. Often these radios were simple two tube regenerative receivers (6SK7) and a one tube transmitter (6V6). One of the more famous of these spy radios is the Paraset shown below.
Developed by the British SAS, it is officially known as the Whaddon MK VII. Often the array of items above were packed into what looks like a beat-up leather suitcase so it could be easily concealed and transported. The name "Paraset" came from the fact these were air dropped with the spies behind enemy lines. Power could be supplied from the mains or a 6VDC car battery using a Vibrator power supply.
Surprisingly it is a two-band rig covering the 80 and 40M bands and with a 6V6 transmitting tube (Crystal Controlled) you could get 5 or 6 watts from the Paraset. Keep in mind the British had an extensive radio receiving network located in Southern England -- so 5 or 6 watts was always heard. Oh, the Morse Key was built into the front panel.
One of the videos showed a man walking down the street wearing a winter long coat with a loaf of fresh bread under his arm. This was not the Paraset, but the Receiver and Transmitter were under his coat and the power supply was in the loaf of bread.
I specifically mention the Paraset because even today it is frequently replicated. Once I even built the transmitter portion of the Paraset and the output tuning has two light bulbs to aid you in tuning a random piece of wire used for the antenna.
During the Cold War refined versions of the Paraset concept were produced for use behind the Iron Curtain most notably by the CIA. You know the same crazy guys who came up with exploding bubble gum.
Today, the Receiver could be a DCR using the Seed Xiao RP2040 and a Si5351 for accurate frequency generation. For the transmitter (VFO control with offset using CLK1) three transistors would give you 5 watts. It could even have a built-in antenna tuner. All of this would fit inside the loaf of bread including a LiPo battery. I would also see creating a coded message that is stored in the Seed Xiao memory and sent as a code burst. Only 2 seconds on the air is hard to direction find.
If I am not mistaken, friend N2CQR while stationed at the Embassy in the UK had a chance to operate one of several Paraset radios owned by Ian, G3ROO.
Going back to the loaf of bread mentioned earlier, this was important as urban legend has it the OSS (forerunner of the CIA) developed an explosive that looked like flour and could be even baked into a loaf of bread and was edible.
Regrettably today I am not certain we have many hams or engineers that could design or build a Paraset from scratch. The under 50 crowd is looking for a kit on Amazon or eBay and would want the Gerber files so the boards could be bought 5 for $5 from China. Possibly they could write the Software for the Seed Xiao RP2040, but the actual fabrication and building of the whole rig in a small form factor is a hill too high or bridge too far. Did I mention that they would want a complete schematic and everything software on a GitHub.
One of the various known maladies of the KWM-2 (did I also mention it sucks on CW) is the failure of the main power ON OFF switch. When this switch fails you are SOL, and I was in that boat!
[ What you are about to read is a solution to the power switch failure that was successful in large measure because of experience, tribal knowledge, and engineering genes. Having some nifty tools like a manual milling machine was also key. Also, significant in the fix is a well-stocked junk box. Soak in what was done as you, the reader, may have a problem like this one at some time and you can refer back to the N6QW solution.]
In the upper left-hand corner of the KWM-2 and KWM-2A is a four-position selector switch that reads OFF ON NB CAL. It is a standard wafer switch but ganged to the non-round shaft of that switch is a second switch which only operates in going from OFF to ON.
We see this setup typically on Volume controls that also have the Snap Action switch causing the ON OFF action to be built into the control. Thus, the ON OFF switch is piggy backed and integral to the volume control.
Collins took a 3 Amp rated snap action switch and mounted it to a plate assembly and mechanically ganged it to the 4-position selector switch. The snap action switch was made by Oak Industries that no longer is in business and the parts are unobtainable. So, you have to improvise and that is what I did.
Original Oak Switch
Essentially someone else came up with the idea (not an original N6QW idea) of adding a mechanical action via a shaft coupler that operates a volume pot with a switch. The pot is not used, but the switch is. So, the problem is how to mount the pot/switch and how to make it work seamlessly. Those are two key words like a beacon on a lighthouse on a foggy night: work and seamlessly!
A second similar approach as seen on the Collins Collectors Association website, uses a 3 Amp Microswitch that is engaged using a flag like device mounted on the shaft that actuates the lever arm of the Microswitch when moving the selector switch to ON.
My approach uses the pot/switch approach but is different in how it is mounted. As with all thing's homebrew, nothing is easy and simply drops into place. Here are some challenges.
1. The Oak Switch is rated at 3 amps. One possible weak point of the Collins approach is that when the KWM-2 was put into service the line voltage was 110 volts AC and today's standard seems to hover around 120VAC. The MTBF for that switch was likely not seen as 66 years. Most Volume Control/Switch units today, are only rated at 1 amp @125VAC. Problem #1, find a switch that can handle 5 or 6 amps at 125VAC. I found a 5-amp rated switch.
2. There are many mechanical issues in arriving at a solution. One of the 1st problems is the shaft on the four-position wafer switch -- it is not round and how do you install that in the round hole of the coupler? A secondary issue is the shaft coupler is metal, and you must insure it does not touch the ring contact on the 4-position selector switch.
In the sketch above we can see the non-round shaft, the void space with the shaft inside the coupler and an insulation solution using a fiber washer where the inside diameter was increased to 1/4 inch to prevent the metal coupler from touching the selector switch contacts.
Problem Solutions!
The photo above shows the Fiber Washer where the inside diameter was increased to 1/4 inch and is placed on the shaft between the selector switch and the Shaft Coupler. Also in the photo are thin sheet metal strips that were cut so that three pieces on each side of the non-round shaft make for a snug fit and fills the void in the coupler. The installation inside the shaft coupler involved the use of a Dental Mirror and small tweezers. The thinner shiny metal cut down to about 5/16 inch was used for the fill shim pieces. The Fiber Washer on one end and the fully round end of the pot/switch shaft captures the shims so they will stay in place.
[The metal filler installation process is best described with a simple analogy much like having a tryst with a 300-pound YL in the back seat of a 57 VW Beetle. Almost impossible. Not totally impossible, but almost!]
Some Luck!
One thing on the Luck side is that the mounting screws of the 4-position wafer switch were extra-long and provide a piece of the solution. Using some aluminum 4-40 threaded spacers, this provided a means to mount a metal plate at a proper distance from the open shaft end that will house the pot/switch. I was able to use the original OAK switch mounting plate as a template for the new manufactured mounting plate so all would be in alignment.
Spacers and Coupler Installed
Mounting Plate Installed
The Pot/Switch arrived yesterday, but I could see already I need to add a bit more "space" between the coupler and mounting plate. I have some longer spacers so that will be the 1st order of business, before final installation.
Longer Aluminum spacers and a couple of homebrew washers enabled the mounting plate and the pot to be at the correct position with the 1/4 inch to 1/4-inch coupler. Everything is rock solid! I fabricated a thick round aluminum spacer that has a 3/8-inch diameter hole and is fitted between the mounting plate and the nut securing the pot. Why? The metal plate is thin aluminum and the washer on one side and the pot itself on the back side in essence "stiffen" the mounting plate so that it is rigid.
The lock tab on the pot housing intended to anchor the pot position on the mounting surface, was bent outward and actually rests against one of the mounting screw heads on the back side. So, as you turn the selector switch CW, the tab resting on the nut prevents the pot from moving in the plate. There was no way to drill a hole in the mounting plate without interfering with something. My solution is an added measure.
Final Assembly & Test
The switch action is smooth and verified with an Ohm Meter. Move from OFF to ON and the meter goes to Zero!
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