Happy Podcast Day! Caveat Emptor!

Today is Happy Podcast Day and a large Tip of the Cap to N2CQR who has had the SolderSmoke Podcast for over 2o years. Bravo Bill, and you can acclaim being on the leading edge with this media communication forum about our wonderful hobby. It has been a honor to ride along with you for a small portion of those 20 years!

This is a Pixie CW Transceiver and certainly can be had at low cost but not at Walmart.com. I was surprised to find out Walmart sells ham gear.

Pixie S but not at Walmart.com 

Having few parts and a PCB it should appeal to our demographic. It is low cost too! 

Basically, it is a kit comprised of two transistors and an IC plus a crystal for operation on 40M. A Crystal Oscillator runs all of the time to supply an LO on receive to a detector as you would have in a Direct Conversion Receiver. Upon keying the circuit, you get a substantial power Output from the second transistor. The downside is no QSY as such and you have but a single frequency radio. 

Worldwide expert homebrewer Peter Parker, VK3YE says the following about the Pixie.

[

The biggest selling (but not necessarily most commonly heard!) QRP transceiver kit would be the Pixie and its variants. Costing less than a takeaway burger meal, it's the cheapest transceiver kit available. The transmitter puts out a few hundred milliwatts CW on a single crystal-controlled frequency (often 7.023 MHz). The receiver is direct conversion with little selectivity. Performance could charitably be described as 'basic' but the design is ingenious, with many parts shared between the transmitter and receiver.

The first question to ask is whether you can make contacts with such a simple affair. The answer is 'yes', with hard work. I class the Pixie as a novelty project, purchased more for the fun of construction than its operating capability. However, if you're persistent, have a resilient sending wrist (for all the calling you'll do) and connect it to a full-sized outdoor antenna then you will work stations hundreds of kilometers away.

So how does the Pixie work? One transistor is connected as a 7 MHz crystal oscillator. It is continuously on, to generate the carrier on transmit and to provide the local oscillator for the direct conversion receiver. The second transistor is the RF final amplifier on transmit. On receiver it operates as a crude detector for the direct conversion receiver. The audio signal at the output of the detector is very low which is why the LM386 audio stage is there to provide some amplification. This is the only stage that operates on receive only.

Other parts of the circuit include the pi-network low pass filter and the transmit/receive frequency offset. The latter is required in all direct conversion CW transceivers and ensures that the transmitter carrier and receiver local oscillator frequency are slightly different so that incoming signals produce an audible beat note in the receiver...

]

If you click on the Pixie CW Transceiver link (earlier in the blog) you will see a you tube video that evaluates this kit. It doesn't do very well and with 5 Volts PTP output that amounts to 62.5 milliwatts. You should be able to see about 10 Volts PTP which now gives you 250 Milliwatts.

While the ham in the video has some really uptown test gear, I am not sure what he saw is accurately reported. I did not see if he had a dummy load connected when he put the scope on the output. I hope his scope is not the dummy load. The output looked pretty crappy. 

For those who have built Regen Receivers you likely are aware they can actually generate RF into the antenna on receive. In fact, the spy operators in WWII using a Paraset had to be cautious of this issue on receive as they could get tracked down.

[

Radiation of RF from Regenerative Receivers

The radiation of RF from regenerative receivers is a significant aspect of their operation. Regenerative receivers utilize positive feedback to amplify the RF signal, which can lead to oscillation and subsequent radiation of RF energy. This radiation can occur when the feedback loop is not properly controlled, causing the receiver to oscillate and produce unwanted RF emissions. To prevent this, regenerative receivers are designed with various mechanisms to prevent free oscillation and ensure efficient operation. These mechanisms include the use of variable condensers, tickler coils, and other components that help maintain the receiver's stability and reduce the risk of radiation. 

njarc.org+5

]

The receive RF signal at the antenna in the video may be a similar issue with the Pixie. 

A real value in the Pixie is to have fun with your "friends". Buy a Pixie for a friend and enjoy the angst they encounter as they try to make it work. I think the video presenter mentions that two other friends have built the kit and saw the same poor results.

The seven-word economic law is at work here:

Them has gets ain't no free lunches. Why do you think the real QRP CW transceivers cost more... because they work. Better yet roll your own DCR and buy a Tuna Tin Two kit from W1REX.

Them that know can make it go. Caveat Emptor!

73's

Pete N6QW

What if you were asked to design a minimum part count CW Transceiver?

What a great question! I wasn't asked to do that, but I don't even know where to start. 

I know of several designs that used but a single device and friend N2CQR took on that challenge, but I think ended up using two devices.

Here is a LINK to a whole lot of CW transceiver projects and one that caught my eye if only from the very clever aspect -- the Toaster CW transceiver. The designer took a defunct toaster case and built a rig inside the former breakfast special enclosure. 

Now in my book he would have gotten extra points if he kept the toaster function AND built the rig inside the case. There is nothing like a warm bagel and bagging some DX.

We started with a minimum part count premise and some of those projects in the listing are anything but simple. I think the operative word is simple as that connotes minimum part count, less opportunities to screw up, a short time from parts collection to on the air. That short time frame solves the instant gratification prevailing feeling among 99% of today's hams... I want it and I want it now!

Simple also connotes topologies involving no filters, no frills and knowing stuff. N2CQR and KK4DAS clearly demonstrated with their direct conversion receiver project that simple is not simplistic. Over 100 units based directly on their design have been built around the world. They even garnered a prestigious award from the ARRL for their effort. So that would be a place to start. 

Later on, the DCR could be upgraded with a Crystal Filter and other frills to provide narrow bandwidth single signal reception. BTW the DCR works well copying SSB signals and coupled with a DSB transmitter now adds a phone capability.

Simple transmitters like the Tuna Tin Two or the Michigan Mighty Mite would be good candidates for the RF generation end of stick.

Rex Harper's, W1REX, TTT Kit

For our demographic described in a recent blog

post you can buy a kit from W1REX so no excuses that you would have to start from scratch!

Now the real problem is how to switch from transmit to receive. It could be something as simple as a DPDT switch. 

The starting point is just that as a vast number of hams are still pondering which end of the soldering iron is hot. CW radios using the DCR and simple transmitters like the TTT, offer a chance to homebrew a radio that has roots in the 1930's. It is also a steppingstone in that converting over to a Double Sideband Transmitter now moves you off the CW only playing field.

N6QW's 20M CW Transceiver 

Them that know can make things go.

73's

Pete N6QW

Projects to Ponder.

What can I do next? I have thought of veering off into a discussion of the mess the majority of American voters made last November. But that will certainly reduce to a small number those who would read the blog. No one likes to hear they did wrong!

Or given my newly initiated Sunday church activity with the Grief Grope I could talk about the stages of grief; but that will certainly turn off another segment. So, with that tangent it is likely I would be writing by and for myself as a single reader of the blog.

Cleverly we have eliminated the supposed two non-subjects to be discussed by hams. 

But the technical side is also a minefield. It would be interesting to develop a demographic of today's average ham operator. Certainly not in the 18-34 demographic for that group has a focus on the third subject not discussed on ham radio.

Our target ham group is older but not necessarily in the licensed for 50 years group. Many are recently licensed hams following retirement. Interestingly many actually have money for the now somewhat expensive hobby. But given the dumbing down of what it takes to get a license the target group is not especially strong with the technical chops. Although likely they may have significant software skills. 

My postings for the last month were a test of the waters. The Mostly Vacuum Tube SSB Transceiver received few emails, and none asked for schematics or even a block diagram. That is a project that could be reproduced but I doubt would ever see a second build by others. The truth is the ham arena has shifted to contests and operating. Hams as a lump group no longer build things!

If my project was presented to QST say in 1975 it may have been published as that was just about the last time such projects were seen as appropriate. As far back as 50 years ago, the influx of commercial gear from the Far East dramatically impacted sales of soldering irons and parts associated with vacuum tube radios.

I am not a contester, and my operating typically is to test something I have built not to rag chew. Or worse those that gloat on the air about the new $7K SDR they just bought and will keep for only long enough until the next bright shiny object appears in QST.

So, if I build anything new it will be just for me and not something to extensively share on a blog. I have a few things that are stirring on the back burner but not suitable for the demographic I described. Today you have to know stuff to do stuff.

Them that know can make it go.

73's

Pete N6QW

The art of communicating one letter at a time!

My recent adventure with Vacuum Tubes suggested the theme of todays' posting. Yes, CW transmitters. Who does CW? Well, not a lot of hams but it is like climbing Mt. Everest... some make the effort.

I am appalled at the cost on junk type CW transmitters on eBay and even after spending a King's Ransom for one you are not done.  Many of the parts like capacitors have reached their end of life and likely the tubes are flat. So, more costs.

There is a bonus to building a homebrew CW transmitter and that is the low cost, small sized power supply from Amazon. You can buy a supply for less (a few pennies less) than $30. There is enough juice in that supply to deliver more 5 to 10 watts to the antenna. That will net pages full of contacts! The linear hunk of iron supplies cost a fortune but with this Amazon supply... it plain works and NO SWITCHING noise in the receiver. You don't have to hit send as I am sure that was a burning question. In one of my earlier blog posts I covered that supply.

There are plenty of good candidate tubes for such a rig and I recommend two: the 6AQ5 as the oscillator driving a 6DQ6 as the final. RF Chokes used to be a problem but with the FT-82-43 cores and 73 Turns of #28 you have an instant 2.5 Millihenry choke. The Mini-Ductor stock can be replaced with the T-68-2 powdered iron cores which easily will take 10 watts (or more). BTW the Amazon supply also provides 6.3VAC at 5 amps which is plenty for the filaments.

A 40M Starter Transmitter

Here is the reason why I suggested the 6AQ5 as it can be used as a standalone rig and then once that is working you can add the 6DQ6 for more power.

If I am not mistaken the older ARRL handbooks (before the handbook became an advertising medium for "Foreign Radio Manufacturers") used to have such a design and it was quite popular.

I replaced the Air-Dux Coil with 22T #20

on a T-68-2 Core and a Better Match!

Since crystals from AF4K cost about $26 I suggest getting the Frequency 7030 kHz as later on you can build this same circuit as a oscillator doubler and now you have two QRP frequencies... 7030 and 14060 kHz. 

For those who have two left thumbs or are just plain lazy the Antique Wireless Association (AWA) sells a 6AQ5 Transmitter PCB on eBay for about $14 and one You Tube video of the AWA rig uses the Amazon power supply. So, no excuses.

Them that know can make things go.

73's

Pete N6QW

Is something wrong with this picture?

I have an extensive stock of T-50-6 powdered iron Toroids, but thought I ought to have a few T-50-2's. So, I navigated to Kits and Parts and a bag of 25 is $6, or less than 25 cents apiece. That sounded pretty good!

Next, I started to complete the order only to find that the weight was 5 grams and that turned into an additional cost of $11.01. The shipping and handling are almost 2X the product cost. I decided to pass on the 25-piece order and instead scour my junk box to find two T-50-2's. [Found one in about 5 seconds.]

Amidon which is about 70 Miles from my QTH wants $14 for the shipping with a similar actual product cost. 

It is funny how one event triggers many others. Recently I stole an octal socket from a power supply for the Hybrid rig and then replaced it which prompted my digging out an old CW transmitter to test the repaired supply which caused me to wind a toroid and that all worked. But I only had one crystal on 7030 which prompted me to look for more crystals. 

Virtually all of the custom frequency crystal companies of old (ICM, Texas Crystals) have gone out of business and what remains is costly do overs. This is where an entrepreneur takes a computer crystal and embeds it in a FT-243 case and puts a Dymo tape label over the case marking the new frequency and charges a hefty fee. The most commonly used types of crystals in ham rigs of old were the FT-243 or HC-6/U.

AF4K Crystals has now filled the gap for many of the crystals needed for ham rigs and whether FT-243 or HC-6/U style the price is about $26 a pop. Likely that cost is real and a far cry from the $3 I paid in the 1970's. But at $26 pick your frequencies wisely.

The same for vacuum tubes that only 5 years ago were cheap but now have moved up in price. Small economic theory here as there is hardly any vacuum tube manufacturing on going in the world, so the supply is dwindling and that raises the prices at the marketplace even for used "toobs".

This is not all driven by the Trump Tariffs, but a realization that many of these products like Crystals and Vacuum Tubes are products of old times and as the supply dwindles, the price goes up. Ham Fests are not the answer either as most of the under the table stuff are computer parts like FDD Drives or Zip Drives and / or 486 processors with a small fan. 

BUT our toroid shipping/handling cost is a result of changes in how small part packages are handled by the USPS or FedEx. Have you bought any stamps lately?

The thrust of this post is the cost of our hobby. While homebrewing provides satisfaction and the opportunity to learn as well as do things inexpensively, the shipping cost cast a pall over that effort. So, future project planning involves a significant evaluation of the shipping and handling cost along with the tariff impacts.

I saw a steal of a Johnson Adventurer on eBay. This was a rig I owned, and it is a superb transmitter with a 6AG7 driving an 807. Gulp the price was buy it now for $30 (typically $200). But the shipping was over $100. Darn!

Them that know, usually do!

73's

Pete N6QW

The Last Posting on the Mostly Vacuum Tube SSB Transceiver.

Spent yesterday doing final punch list items like installing the bottom plate and anchoring in the power supply cage cover. This has been a rewarding project insofar as addressing the many small obstacles and technical issues. Regrettably this project is somewhat depressing as it also now fully convinces me I should have gone into the amateur radio equipment manufacturing business. Too late now.

In giving this a bit more thought the whole project involved an Engineering Team consisting of one person... me. Just think what I could have really done with a bigger team.

There were no kits or BOMs involved, and the rig has parts from over 55 years ago, while at the same time it blends mostly old technology with new technology. It required writing CNC software to cut the various metal pieces and a lot of engineering and tribal knowledge to pull it off. In essence this was a totally homebrew project including the power supply. One of the nicest comments I received was that it looked factory made

A bit of info on the 12GE5 RF Amp stage. The Plate voltage is 500VDC, the Screen at 280VDC and the bias set to deliver 25Ma of Cathode current. The Bias to the rig is -120VDC. The Bias network connected to the tube has the range to deliver 25Ma of Cathode current. 

I did not have a 6.8K 2-watt resistor so I paralleled four 27K, 1/2-watt resistors and that worked FB. The Cathode Meter is a 0 to 200Ma unit and it connects to Pin4 on the Plus side, and the Minus side is connected to ground. Pin 4 and Pin 10 each have a 10nF, 1KV ceramic cap to ground. Again, the Meter on the Plus side to Pin4 and the Minus side to Ground.

The 20nF cap connected to the 6.8K and the center wiper on the bias pot actually puts that resistor to ground for any AC signals.

The plate circuit is not built as shown on the sketch. The inductor is a HB choke (227 Uhy , 24T #2o on a FT-82-43) and it connects to a parasitic choke comprised of two 100 Ohm resistors in parallel that have three turns of #24 wire and that connects to the plate. 

At the junction of the parasitic choke and the RF Choke you connect a 1000pF 20KV cap which feeds a Pi Network. The Pi Network Tune Cap is 150pF and the Load Cap is 1000pF comprised of a 600pF trimmer cap in parallel with a fixed 330pF cap. The Tank Coil is 15 Turns (8 TPI) and 1.25 inches in diameter. Pin 12 on the Filament is grounded. The feed from the IRF510 into Pins 3/11 Via a 10nF passes 1st through a W3NQN LPF. 

For added safety a Home Brew 2.5 Millihenry RF Choke is connected from the Pi Network to ground in the event the Plate Coupling Cap shorts you would have 500 VDC on your antenna. The RF Choke would shunt that voltage to ground. The RF Choke is 73 Turns of #28 on a FT-82-43 core AL = 470

The Stainless-Steel expanded metal screws into the angle stock.

Nice and Safe!

Bottom Plate with Countersunk screws

Fit Check of Rubber Feet

I have been back at the Sketch parameters and did a bit of fine tuning on the BFO frequency. It sounded a bit nasal and pinched and I made some changes there. But for the most part we are done. Well, my rigs are always built as experimenters' platforms and so never done!

So, this is the recovery from the ill-fated Transcom SBT-3, Project X and it helps that this Mostly Vacuum Tube Wireless Project was successful.

Them that know, really do know and can make it go.

73's

Pete N6QW

First Contact with the Mostly Vacuum Tube Wireless Set.

Yesterday at noon, I checked into the Jefferson Noontime Net. The net control station was in Petaluma, CA, about 400 miles from me. I got a 5X9 with good audio quality report. 

Petaluma in case you didn't know was the film location of the movie American Graffiti and is home to the Petaluma Poultry Processors. The PPP used to have a large sign in front of their plant location declaring: We use every part of the chicken except for the "cluck". Despite what you may have heard, chicken blood is not used as a coloring agent in ladies' lipstick.

Spent yesterday doing some clean up and further installations like a safety cage around the open power supply. Below are more photos of the actual build. BTW no one more surprised than me to see my 12GE5 Final Amp design worked.

Top View of the Homebrew Rig

Rig and Power Supply

Open Power Supplies. See later photo.

Separate Band Pass Filters

The liberal use of cable ties.

12GE5 Underside. Note the HB RF Choke 227 Microhenry

22 Turns of #20 on a FT-82-43, AL Value of 470

The two Blue Caps are 1000pF at 20KV

Pre-Driver, Driver plus LM380 Audio Amp

Power Distribution Board

Safety Cage Over the HV Power Supply

One additional install was the transistor switch to key up the SB-200 Amp. Using the outboard amp (10dB gain) I am thinking maybe 300 watts into the antenna using this outboard amp. This is exciting.

Them that know, really do know!

73's

Pete N6QW

The Mostly Vacuum Tube Wireless: Some final tasks before the Big Smoke Test.

This project was a bit more complex than most of the stuff I do. You ask why? Well, I had a bunch of working modules on a wooden board that had to be refitted into a homebrew enclosure and still work after reinstallation. I needed a special power supply that had to be designed and built, and I also had to design a vacuum tube final amplifier.

It is one thing to 1st determine a size of an enclosure and then create the electronic modules to fit that real estate envelope. The other way around is to have all the modules that are spread out on a wooden board and then try to mash that "blob" into a reasonably sized enclosure. This latter approach is more difficult. 

Nearly Completed Mostly Vacuum Tube Wireless

This is where it started!

Proof of Life!

I am pleased at how the rig looks, but it took a lot more noodling to figure that out. I can see some wasted space but for the most part all of the modules were already built, and this drove the final configuration. I tried to place the most frequently used controls so that they could be easily accessed. With my FFS, (Fat Finger Syndrome) Big Knobs was the order of the day. 

I did a recheck of the power supply and especially the power plug wiring. Accidentally putting 500VDC on the Filaments will kill the project, so the wiring has to be right!  

This recheck did uncover a small wiring error in the BIAS supply. It would not have been catastrophic but would result in too high of a value. The power transformer has one other winding other that 520VCT and that is 6.3 VAC at 3 amps. The filaments are wired for 12VDC so that winding was initially unused. 

But then I had to have a -60 VDC bias for the rig. So, a lightbulb went on as I bought a 12.6 VAC small filament transformer. By pumping 6.3VAC (power transformer) into the 12.6VAC side of the filament transformer the primary side is now the secondary and we have 60VAC which can be rectified to deliver -60VDC. 

The 12.6VAC side has a center tap and that was the wrong connection. I was pumping 6.3VAC into 1/2 of the filament so the secondary voltage was 120VAC. A simple wire change now produces -60VDC for the BIAS and cutoff supply. Always a good thing to recheck wiring! 

[Later when I was testing the transmitter the -60VDC was not enough to set the bias level so back to the original wiring and -120VDC. Now I can set the idling cathode current to the proper level (25 ma).]

Bias Supply Wiring Change

The power plug wiring on the main rig chassis was checked and rechecked with the intent of no HV pumped into the filament circuit. The plan is to initially not connect the plate supply of the 12GE5 into the power socket and to remove the 12GE5 from its socket as 280 VDC is relay switched to the screen grid on transmit.

The initial Big Smoke Test will essentially check all of the circuitry that was formerly installed on the wooden board. The output of the LPF from the IRF510 in normal operation is connected to Pin 3 on the 12GE5. 

For the initial test I will connect a 50 Ohm non-inductive 15-watt dummy load to Pin #3 to do all of the initial transmit and receive tests. Caddock makes the non-inductive resistors for the dummy load available at Digi Key and Mouser. The Proof of Life video passed the test and no smoke, but I only looked at the receiver.

I need to do some more work before hitting the Transmit button. Stay tuned! Who Can Wait... so check out the video below. With a bit of circuit peaking I get 25-30 Watts PEP to the antenna. 

Transmitting

I am a happy camper and still going through shakedown but encouraged with the results so far. Even though I used a choke input filter there is a pretty substantial sag in the plate supply to the 12GE5. No load there is about 550 VDC on the plate of the 12GE5. That drops by a hundred volts key down. With a consistent 600VDC (and more current) on the plate I suspect we would see 40 watts out. The Hammond Transformer is 520VCT at 104 milliamps. I am seeing a cathode current of 150 Ma. on tune up and voice peaks. Simply stated I need a bigger transformer!

Them that know, really do know!

73's

Pete N6QW

No work done on Sunday but something did arrive from Amazon.

Confession Time! I smoked my Analog Multimeter (VOM) as that what happens when you put 500VDC across the meter when it is set to measure Ohms. I purposefully bought this VOM for use with high voltage so I wouldn't smoke my expensive DVM. 

My plan worked, but now I needed a replacement VOM, and this is the jewel from Amazon. You get a lot of capability for $30 including spare fuses inside the case. It even has a powerful magnet on the back so if you put it on a magnetic surface it won't move like when you are working on a car.

A New VOM for N6QW

Here 1s an interesting proposition for those whose only amateur radio activities are contests and operating. Since you don't homebrew you have do something with your license. 

There are declared Micronations within the United States and one of those is in California known by the name the Republic of Slowjamastan run entirely by the Sultan of Slowjamastan. It is complete with purported land mines and where the wearing of Crocs is outlawed. [I am not making this up and it is not April 1.]

So here is the proposition... A permanent DXpedition to the Republic of Slowjamastan and get this call sign, K6SJM. You could charge for QSL Cards and be sure and cut in the Sultan for a piece of the action. His day job is in commercial radio, so he knows about hams.

Believe it or not, there are hundreds of declared micronations in the USA including such entities in the states of Texas, Utah, Nevada Ohio, Vermont, New York and Washington. 

Are you listening ARRL here is an opportunity to sponsor MINOTA events. MINOTA = MIcro Nation On The Air. This could be a lot more fun than POTA or SOTA. ARRL, you could even go so far as to entice your offshore advertising sponsors to create a premium cost special MINOTA rig.

Slowjamastan has no permanent residents save for the Sultan, but other Micronation's actually have a significant number of full-time residents. I was told that one of the Micronations was founded by the guy who invented the Segway. This is serious stuff.

I can hear it now: CQ MINOTA, CQ MINOTA, this K6JSM, calling CQ MINOTA from the Republic of Slowjamastan. Special points for a MINOTA-to-MINOTA contacts.

Them that know make things go.

73's

Pete N6QW

Lots of work done on Saturday. About 90% done with the wiring and hookup.

I needed to get lots of work done on Saturday as I will be at our local Catholic Church sponsored Grief Group today, (Sunday) and that creates a big hole for any ham stuff. 

A surprise from the 1st Grief Group Session was that here it is a special Catholic Church Event, on a Sunday and no one passed the basket to squeeze a bit extra out of my wallet. I should count my blessings.

Basically, I accomplished the following on Saturday:

Wired the 12GE5 socket complete with the Bias network. Installed and Wired the Pi Network. Connected the Receive and Transmit Band Pass Filters as well as the Cathode Meter. Work remaining is the hook up of the power connector wiring. But I want to do that when I am fresh.

Pi Network Compartment

Rx Tx Band Pass Filters

Most of the Under Chassis Wiring

Slightly Different View of the BPF's

Top View of the Mostly Vacuum Tube XCVR

Power Plug: Fit Check for further wire dressing

Finally, is a case of robbing Peter to pay Paul. I lifted an octal socket from a power supply so I could finish the mostly vacuum tube wireless power supply. The replacement arrived which I installed Saturday and thus a check of its functionality with an old CW transmitter I built long ago.

I was surprised at how good the CW transmitter sounds. It puts out 6 watts. Ignore the crappy sending.

CW Tx

Them that know can make things go. 

I also went grocery shopping yesterday. It was awful... the result was but a few staple items in the cart that cost a lot of money. To the "majority who voted for this condition" what have you done? My only solace is that you are having to pay too! This appears to be more than a blip on a chart.

73's

Pete N6QW