December 31, 2024. Last day of this year. Time to spend some money.

 

Meet the $800 Xiegu X6200 Appliance Box Radio 

This is a QRP radio with an internal battery that will produce 5 watts before a recharge (typically 4 to 5 hours) and touted as PFP (Perfect For POTA). It has a 3.7 out of 5 rating with several complaints like not good for CW ops and non-functioning out of the box. Who would buy this radio?

Well likely lots of potential purchasers would. One of its advertised features is small size which is a boon for those who do not suffer from FFS (Fat Finger Syndrome). Yet another is that it is a Direct Sampling SDR which means that you must update the radio frequently to get the latest fixes to the problems that were inherent when shipped from the factory. 

Hate to say it but you could get an ICOM IC7300 for less money and despite also being an appliance box has a proven track record. 

I chose this subject and rig for today's spotlight if only to say choose wisely and read the fine print. I have an old car and likely the chewing gum and bailing wire fixes are at EOL (end of life). It is a Toyota Avalon with mileage close to 200K and 19 years old. But a couple of items that would need to be addressed near term, will cost about $5000 for a car with a bluebook value of less than $2000.

My kids at Christmas jumped all over me about buying a Tesla M3. That is some slick advertising -- my #3 (Mechanical Engineer) whipped out his phone to show me that a $43000 MSRP M3 out the door was only $31000 with the rebates and savings.

Read the fine print as that price only applies to a black car with a black interior and the $12000 price reduction includes the $7500 rebate and a calculation that you will save $5000 in gas in California over some specified time. That $5000 is not immediate and is purely a suggested savings and not up-front cash in your pocket! BTW any other color of car or interior (white interior is the only other choice) adds one to two thousand dollars to the price tag.

So, the out the door price is the $43000 (black car and black interior) + the dealer prep, shipping, taxes and $420 for floor mats and $35 for an upright interior tray table, plus $420 for the home charger and the range is only 300 miles. 

It looks like the $31000 M3 will be about $38000 to drive off the lot. But it has 510 horsepower and can do 0-60 in 4.9 seconds. It also has 23 cu ft of storage space and no more oil changes. 

The last thing I need to do is put money in Elon Musk's pocket -- you know he is the guy who is trying to put you out of work if you are employed in government service. He is also the guy protecting his foreign tech workers with the immigrant special visa arrangements. My oh my decisions have consequences, so look what you got if you voted for what's his name.

I still need a new car but as my #3 son (smart guy) said: Change the oil, rotate the tires and make sure the brakes work and forego the expensive repairs. Drive it until it dies and only then spring for a new ride. Today it is worth less than $2K so not a huge trade in!

Are you really going to spend $800 for a 3.7 out of 5 rated radio that is only 5 watts and works for 5 hours on a battery? Think hard!

Happy New Year.

73's

Pete N6QW

December 30, 2024. Throwing down the gauntlet challenge ~ A Thermatron Direct Conversion Receiver

With lots of time to think, but little time to build, and as we close out 2024, my thoughts turned to "why not a vacuum tube version of a Direct Conversion Receiver".

Friends N2CQR and KK4DAS caused this thought aberration as they embark on a 2025 community build of a solid state DCR. Mind you this is just N6QW having a lot of time to think.

Firstly, FOAM is still valid as a driving concept: Filter, Oscillator, Amplifier and Mixer. I see four tubes would be needed. Two 12BA6's, one 12AX7 and one 12AQ5.

One 12BA6 would be at the RF Amplifier spot with the second 12BA6 used as the LC Local Oscillator. The 12AX7 would be used as the Product Detector and Audio Pre-Amp. Finally, the 12AQ5 is employed as the Audio Output Stage.

The beauty of this specific topology is that much of the circuitry already exists for these FOAM elements. Some of these circuits are sitting in my Hybrid SSB transceiver design. No High School Science project involved here. The toughest part is the Local Oscillator and keeping that stable. But that is the same problem with a solid-state version.

We would have to use 12VDC on the filaments to address any hum problems and the plate supply can be something as simple as a 125 VAC to 125 VAC Isolation transformer in a full wave rectifier circuit with a hefty filter on the output. The current draw for the plate/screen would be something less than 50Ma and a 100 Volt Zener would stabilize the supply voltage to the LC Oscillator. For the front end we could use a 40M Band Pass Coupler (design exists).

Now a potential slick trick for the LC Local Oscillator would be to run it on 80M and using a diode doubler create a very stable 40M LO. 

[A 17M SSB transceiver design of mine which used a 4.9152MHz HB filter needed a 23MHz LO. I built a 11.52MHz Super VXO and diode doubled that to give me about 40 kHz right in the middle of the 17M phone band, so I know that the doubler solution works!]

Here are some of the circuits that would be used in the Thermatron DCR. These work! We could entertain using a third 12BA6 as the audio amplifier stage which would give an output on par with a LM386. I investigated the 6BA6 as an audio amp stage and that exits in hardware. 

So, there are two burning questions that surface. The first is why the Vacuum Tube DCR and the second involves serious psychotherapy for N6QW. The first question is that while I haven't done serious deep diving on the internet, I haven't seen any tube DCR's. Possibly since the DCR hit the streets in 1968 and was solid state it never started as a vacuum tube design that migrated to solid state. 

The portability of the solid-state is a huge factor when you think about a POTA op using CW and a DCR. A $15 DC to AC inverter from Lauren Sanchez' boyfriend would resolve that problem -- but more hardware to lug to the picnic bench.

N6QW has always been a few corn flakes short of a full bowl so no psychotherapy required or needed.

A project like this could be the seed for an evolutionary development like adding a mating transmitter. That 12AQ5 would be a Jim Dandy 5-watt transmitter tube and with some intermediate circuits (also existing) the DCR can be turned into a superhet with a HB crystal filter.

I see a project like this as a means of "coping with the chaos" that soon will infest this once great nation. Those that chose that option, what have you done? 

Happy New Year.

73's

Pete N6QW

December 29, 2024. A response to the soon to be Tariff Impact.

The always and forever is the better mousetrap! A tour through eBay yesterday was an eye opener.

I actually was looking for crystal filters and saw a bunch under the ICOM section. The FL-30, a 9 MHz, 2.3 kHz wide SSB filter can be found in many ICOM rigs of the past. These are currently priced in the $20 to $30 range. For tighter skirts the FL-80 is a good selection.  A tighter skirt on a shapely YL is better and so take the hint when it comes to filters.

My tenet for those 1st time builders who want to build a SSB transceiver is that you buy a commercial filter as a first step build. After you get your homebrew rig working and working properly, then and only then, take up the science project of homebrewing a filter. 

You want your very 1st HB rig to be a success, and a commercial filter puts you way up on the curve. Later on, you can fiddle and fool around with the math and crystal selections and even use that untrustworthy Nano VNA you have.

I have several radios with homebrew filters, and they work FB because I know what the rig can do with a commercial filter first. My choice for a HB frequency is a filter at 4.9152 MHz --- just like in the Elecraft K2.

But while touring ICOM, I spotted several offerings from China for the ICOM IC7300 for less than $600. It's clear they have product they are trying to dump before what's his name Tariffs kick in. I even saw one NIB IC7300 for $19. Yes, $19 but the shipping was around $650. 

Now is that a way to beat old what's his name Tariff plan? Does the tariff exclude shipping costs because that would be one sure loophole? The Oriental mind is very good at business, and I am sure they know the tricks to avoid tariffs -- $669 is a great price for a IC7300 for those who can't resist the appliance boxes and lack the technical chops to actually build stuff. Regrettably those two factors are a common set amongst a large segment of the US Ham population.

The $600 price tag on an ICOM IC7300 is sure to give DX Engineering and Giga Parts some heartburn as their price range is about $400 higher. (America will be great again with higher prices.) Then a clever option will be to set up stores just across the US/Canadian border and sell the $19 IC7300 with the $650 shipping cost.

Better mousetraps always bring a smile to my face, and I can see the $19 radio as a great clever idea!

73's

Pete N6QW

December 27, 2024. It is time to resist. Join the Resistance Movement!

This is not a political posting but instead an opportunity to address some serious issues concerning our hobby.

At one time it was not the number of hams who were licensed that was the metric but that those who were licensed hams all had a level of technical chops. The ARRL in a move to increase advertising revenues fostered the get more hams licensed by dumbing down the licensing requirements. 

ARRL's own data shows about 770,000 licensed US hams today but only half of that number have full HF privileges. The rest have a Baofeng UV 35R handheld.

Many of the technical advances in our hobby during the period 1940 -1970 were a direct result of ideas and products developed in ham shacks across the US.

Some Internet Data (not independently verified but likely close).

1939 about 51000 US licensed hams

1950 about 90000 US licensed hams

1956 about 140000 US licensed hams

1970 about 270000 US licensed hams

2024 about 770000 US licensed hams

So, what this tells me is that there was a 5-fold increase in the ham population in the 30-year period, 1940 - 1970. But in the 54-year period from 1970 to today it is only a 3-fold increase. 

The US population in 1940 was 132M where the ham population is 0.04% of the US. In 2024 we have 330M and the ham population is 0.02%.

Despite the BS from the ARRL, our hobby is not growing commensurate with the growth of the general population and today's hams do not have even the basic skill set that existed in 1940. The sad fact, the new hams of today simply are not interested in gaining those skills. You ask why? Simple -- it is too easy to get a ticket today.

The blame lies with the ARRL so resist any and everything ARRL. Dump your membership and you will not burn in hell for doing so.

The next resistance is to stop buying those appliance boxes from the Far East. US hams put MFJ, Collins, Drake, Heathkit, National, Hallicrafters, Atlas and Ten Tec out of business. Yet on the used market these are some of the best transceivers/equipment that can be acquired and put back on the air. Oh, but you need skills to do that which you didn't need to get a license.

Finally, resist the idea that you cannot homebrew a modern radio. You can do it! For the longest time ARRL touted you cannot build a quality receiver at home. If they did suggest homebrewing receivers, the plain truth, they would lose advertisers.

A Homebrew Modern SSB Transceiver

On the political side, too late to resist and a bad choice is just that and you will have to live with it. Already you can hear grumbling of what is likely to unfold from those who voted for that person. I say again -- too late!

Happy New Year!

73's

Pete N6QW

December 26, 2024. I got a SUV present for Christmas.

 

Another Christmas and another SUV present -- Sox, Underwear and Vitamins. I did get some neat presents though including a book by Mark Harmon (NCIS alum). The book is about WWII entitled Ghosts of Honolulu. It should be a good read.

Speaking of NCIS (Naval Criminal Investigative Service) during my last tour of duty in the Navy I had a collateral duty as Legal Affairs Officer and routinely worked with the NIS (Naval Investigative Service) the forerunner of NCIS. About two months before I was to complete my four-year obligation, they tried to recruit me to join their organization. I asked one question well actually two. Number 1 was what was the pay and Number 2 would I have to carry a gun. The pay was poor, and the gun answer was always. 

I gave my country four years of my life and so opted to work for AT&T Long Lines. That was a good choice. 

Kind of a year-end rant. I don't like what I see shaping up with the new government that in less than four weeks will assume power over all of us. For those who opted for that choice, like I told my kids when they were young, you will have to live with the choices you make. What were you thinking for those that chose this option?

That takes me to Microsoft. My computer got switched over, without my choice, to Outlook. My email is in a shambles and Outlook is a dismal failure. Bill Gates what were you thinking?

The collapse of MFJ this year was a sad note that signals the loss of a major US ham product producer. What will happen to Elecraft and FLEX as the tariffs take effect? Many of their parts come from offshore. That ICOM IC7300 soon will about double in price so I hope you got one for Christmas. 

Virginia Hall, WWII OSS Spy and Radio Operator

The above portrait of Virginia Hall is one of my favorites. Hall who had a wooden leg a result of a shooting accident is a famous heroine of the WWII Spy community. Note the suitcase radio and the converted bicycle generator. That radio rig would be a good candidate for a POTA or SOTA event.

Here is wishing you all a Happy New Year. 

73's

Pete N6QW

December 24, 2024. Twas the night before Christmas!

Twas the night before Christmas and there was no RF in the Shack! No RF is a good thing too! 

Christmas is a time for family and to reflect on the good things and perhaps cleanse away the bad things (that is the more difficult task).

We should never take life for granted as there may actually be no tomorrow. So, enjoy the good stuff today and maybe use this time to chart a project for 2025 where you actually build something.

Actress Terry Moore circa 1947

The world is unfair. I have many projects I would love to build but have no time given my caregiver duties. Yet you couch potatoes out there have the time but no interests other than looking at IC7300 Menus. 

Several days ago, I posted a photo of Terry Moore, the actress. No one flinched or asked why! In the early 1950's Moore was part of a USO tour entertaining our troops in Korea. It was winter and Moore appeared on stage in a white ermine bathing suit. It was a big hit with troops but not taken well by the WCTU (Women's Christian Temperance Union). 

Having been deployed twice to a war zone, my only criticism is that it wasn't a bikini. One publicity photo shows Moore in the ermine suit, standing between two guys wearing arctic parkas. Moore is alive today and on January 7, 2025, will be 96 years old. Happy Birthday, Terry.

Merry Christmas to all.

73's

Pete N6QW

December 23rd, 2024. It is with a sad realization -- the era of homebrewing is almost extinct!

The era of homebrewing a rig is very much on the decline if not almost gone. Perhaps less than 1% of US hams ever build anything. (That set is about 7700 hams and possibly much less than that as 1% of the US Hams with HF privileges is half that number or about 3800.) 

N6QW's 40M DCR ~ MC1496 Based

The availability of ham radio products literally overnight is staggering. If it is not something advertised on eBay, then Jeff Bezos has it. Typically, the pricing is pretty fair and thus no need to whip up something in the lab. You can buy it and have it in hand faster than you can make it.

[My daughter had an accident a week ago where she broke a rib and was in the hospital for two days. She is OK now, at home and will be joining us for Christmas. We all know about hospital food -- so she got Door Dash to deliver her food in the hospital -- all she took with her to the hospital was her iPhone and a Credit Card. Same thing with ham gear and electronic parts.]

Then there is the pervasive view: "I really don't have to know how it works ... I just have to know how to scroll through the appliance box menus". Set everything to 11 and you will be heard!

A fallout from the lack of homebrew activity is the pride in saying my rig is homebrew during a QSO! On the other end instead of a complement that someone actually has the skill set to build a modern radio the response is: Well, I guess it sounds OK for a homemade radio.

The other huge hurdle is the knowledge base to build electronic hardware. That does not come overnight. Time is the key factor, like time spent learning and understanding. Time spent at the bench is another factor. It is almost impossible to scratch build (not a kit) a totally homebrew SSB transceiver and have it work at turn on when this is the 1st project you ever built! Starting small is the place to start but the impatience of many hams hinders starting small. 

A sub-set of this impatience is that many newer hams have roots in software and make the assumption --software / hardware there is no difference! Possibly for some but not a 100% transference.

So, while in yesterday's posting I suggested homebrewing a DCR CW transceiver, what was I thinking? It will be a huge hill to climb just to get a few guys to build a DCR receiver. A complete DCR CW Transceiver may be a bridge too far. 

But as was pointed out to me by one regular blog reader a complete homebrew DCR CW Transceiver has been published in the latest QRP Quarterly. In a perverse twist of fate, it uses the MC1496 and the author states in the closing paragraphs his project was based in part on my work with the MC1496 DCR published several years ago in SPRAT.

You might want to drop KK4DAS an email about his DCR Buildathon and the schedule dates.

73's 

Pete N6QW

(1 of the 3800)

December 22, 2024. So how do you turn a Direct Conversion Receiver into a Transceiver?

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!

Happy Holidays.

73's

Pete N6QW

December 21, 2024. "Miss Congeniality"

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!

73's

Pete N6QW

December 20, 2024. A Case for Zuppe Inglese

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. 

73's

Pete N6QW

December 19, 2024. The Day After.

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.

73's

Pete N6QW

December 18, 2024. Happy Birthday Brad Pitt! More on the KWM-2 Switch Fix!

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.

December 17, 2024. WWII Spy Radios

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. 

https://www.youtube.com/watch?v=-PsdLyK8SQM

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.

73's

Pete N6QW

December 15, 2024. New You Tube Video Just Added!

You Tube ~ Power Switch Repair

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!

When You Know, You Can Make It Go!

73's

Pete N6QW