January 17, 2024. Time to build stuff.

Our hobby can only move forward if there is a cadre of hams who are filling the well. Early on the allure of ham radio was the pure adventure of advancing the technology. A One Tube transmitter soon advanced to multi-band, multi-stage radios where something more than QRP was putting fire in the wires.

But today the technology is being advanced by corporations, not hams and the hams have given way to knowing nothing. (Thank You, ARRL.) But they do spend huge sums on radios they know nothing about let alone how to operate them properly.

Challenge yourself to build something and here is a small one and done project that has many uses. Cheap computer crystals work well in this circuit. This is not an original design but something I think I lifted from W7ZOI. Caveat -- likely good for most crystals in the HF range but might not work in the 2200 Meter band nor on 430 MHz.

The genesis of this transistor test oscillator was in connection with the fabrication of a 40M high performance CW transceiver. I needed a test circuit early in the build to supply the BFO input, to align the IF, to set the BPF on 40M CW and as a general weak signal source once the whole rig was built. As things usually happen the 1st thought was to build a better receiver (something more than a regen). But as time went on and I saw how well the receiver worked -- the project got bigger. A line from the link that details the project. 

What started as a receiver project has ended up a small sized feature packed transceiver. 

The 5.185 MHz was the IF and the 7.030 MHz was for testing the Mixer, BPF and overall gain. As a weak signal source, I placed this unit in the back yard operating with a 9VDC battery and was able to peak the rig to hear the signal.

https://www.jessystems.com

The link has the build details of this 40M CW Transceiver.

As I now look at this design and the project, it is really sophisticated with the NE555 TR Switch (SSDRA), the FET audio muting and the integration of 4 MMIC devices into the rig. The VTO (VFO) running at 2 MHz made for a stable signal. The offset was done with a separate Crystal Mixing scheme in the transmitter. What I didn't think of at the time was a two-band rig as the shifting the VTO down in frequency and a new BPF and LPF gives 80M CW. Today this project would be ripe for an Arduino and Si5351.

This project is a simple one transistor Colpitts Oscillator with output taken from the Emitter. I used this device for the following purposes:

• Weak signal source for determining if a receiver is working.
• Aligning Band Pass Filters.
• Code Practice Oscillator.
• Signal Injector for testing various modules in a receiver.
  
• With a reconfiguration and adding a Low Pass Filter -- a QRP transmitter
• BFO for a receiver
• CIO (Carrier Insertion Oscillator) for a Balanced Modulator.
  
• In connection with an SDR to measure crystal frequencies for selection of devices as being close enough for a Crystal Filter

These are but a few and you can add your own to the list.

 

The cost is low and with a bit of reconfiguration even its PNP brother could do the job (2N3906).

BTW Mouser and Digi-Key sell crystals that can be used as BFO/Carrier Oscillator devices for a 9 MHz Crystal Filter. (8998500 and 9001500). The switch can select USB or LSB.

 

Show your stuff and build this jewel. 

In a subsequent posting I will show how to build an RF Probe that can be used with a VOM to sense and relatively measure RF output. By this I mean you can see A is much bigger than B, but the actual value is not precise. In most cases hams want MORE, and this will tell you if what you changed is MORE!

 

73's

Pete N6QW

January 16, 2024. Done In!

 When It rains it pours! Done in by the obscure.

4 Pin Microphone Plug!

Christmas 2022 I was given a Tech Special Drake TR-7 from my #2 son and his XYL. The repair involved a $0.38 24VDC three terminal regulator. 2023 sucked insofar as ham radio is concerned as my time was devoted to the health issues of the XYL. 2024 so far is a rerun of 2023.

 

Christmas 2023 I thought I would fire up the Drake TR-7 like a sort of a celebration.  It didn't work on Phone but CW was OK. A look at the schematic for the Transmit board indicates the phone portion could be defunct but CW would work. Drake advises --get a replacement board is always a good idea versus trying to troubleshoot a board outside of the radio. I found a reputable eBay supplier that I had purchased other boards from in my initial foray into fixing the TR-7. I went to him.

 

The 1st thing I did was to pull the microphone out of the short adapter cable (stereo to four pin) and ran it into another rig. It was good so lacking lots of time I just ponied up and after a bit of haggling with the supplier bought a replacement board. 

 

I installed that board which is like wrestling an alligator as the Transmit board sits underneath the display board which is hard to get back into place because of all of the pins that have to align. But I did it and on power up yesterday --same issue. 

 

That is when I thought the one thing I didn't check was the short adapter cable and sure enough the microphone lead was broken at the solder lug inside the 4 pin connector. The reason I didn't look at that initially was that the way that is installed there is no strain on that wire or bending as the cable is literally captive inside the connector body. 

 

A stereo type connector is always suspect and I did check that side of the adapter cable previously and it was good. A bit of lead dress and a re-soldering of  the wire to the lug on the 4 pin and we are good to go.

 

There are two VCO's in the TR-7 with one operating below 15 MHz and the other above. Now we have a VCO problem on the higher bands. When you go to 15M the LCD reads 16MHz and when You got to 10M the LCD reads 23 MHz. The frequency mixing scheme does include a 5 MHz component which is the IF frequency. So the 2nd VCO might be good but the 5 MHz IF signal is missing on the higher bands. More troubleshooting as I may have disconnected something when I pulled several of the boards to swap out the Transmit board.

But there is another key point and that is before you undertake drastic steps like buying a spare board and ripping her open, I should have checked both ends of the adapter cable as this was easy to do and I would have saved a lot of money, grief, time and now having to find and fix a second problem. Shame on me!

 

When it rains it pours. While good for advertising like Morton Salt does, it is not good for our ham rigs.

 

73's

Pete N6QW  

January 15, 2024, ARRL/QST does it again!

Yesterday's posting mentioned Ben Vester's 20M Homebrew SSB Transceiver circa June 1963 (page 27) and how it was rated at about a puny 250 Milliwatts with a 2N706. (A correction to my earlier 100 Milliwatts.)

That particular rig appeared as a QST Article (June 1963) and then included in a later version of the Single Sideband Handbook. I did not see the original QST article but did see the rig in the SSB Handbook. 

 

Man I couldn't wait to get my hands on some parts to build that jewel. I did build it and it didn't work on transmit. For the life of me I could not understand the why. I checked all the wiring and the devices -- but no RF. 

 

I had mentioned to one of the Editors at QRP Quarterly the difficulty I had with the Vester build as I also had in the queue my Shirt Pocket SSB Transceiver article.  The plan was to compare Vester's work (1963) with my own in 2011.

 

The Comparison 60 years Later!

 

Vester = 70 cu in. N6QW = 24 cu in.
 

He sent me a copy of the Vester article and in 10 seconds I saw the problem. The SSB Handbook had a wiring error. Look at the primary side of L20. In the SSB Handbook the bottom end of L20 (Primary side) is grounded but in the QST article it is not!

So once again today's poor homebrewer suffers under the negligence of the ARRL Technical staff. Too bad that didn't work as that would have been a cool project. 

 

I missed the June 1963 article as that was a busy time for me as I was commissioned an Ensign, USN, on June 3rd, 1963, and soon to head off to Midway Island. 

 

Midway had 3000 personnel and SIX single women. These were schoolteachers and three of the six were in their 50's. Two of the good-looking younger ones were always on the invite list for any event. In retrospect those two must have thought they indeed were living in paradise.

 

One of the over 50-year-old teachers always seemed to sit at my table at the BOQ Dining Room. I got more than a distinct impression I was on her invite list. Her pickup line (she taught Home Economics) "how would you like some homemade cookies?" 

But fortunately, being the most Junior Officer on Midway Island (still 21 years old) I was always on the Watch List on weekends and holidays -- so I could honestly say I have the duty -- which for 98% of the time was true. When I made Lt(jg) -- that all stopped but I was no longer on Midway.

Other fond memories of Midway were being OOD on Christmas eve and the 13-inch rat caught in my room in the old BOQ built in 1941. That event qualified a move to the new BOQ.

You must ponder any future ARRL/QST subscription as they likely have moved past their prime (long ago for that matter).

Spotted on an Internet Pop-Up:

No McDonald's?

Iceland is truly a special place on the planet with a steady population of 360,000, and not one single McDonald's. That's right, the last McDonald's closed in 2009 and a new one hasn't opened since.

73's

Pete N6QW

Talk About Stuffed to the Gills.

 

January 14, 2024. A SSB Project.

 Build it? Buy it? Or Plain Forget it?

Like a 1940's Radio Mystery where all you hear was sound effects, but yet it was so real that you felt you were part of the cast. The key difference is our internal imagination that transports us right into the scene. It is like we are in the studio up close and personal. You need no imagination to watch TV!

Scratch Building and Fabricating a SSB transceiver requires that same level of imagination. You find yourself literally transported right into the innards of the rig. Here you look at the circuit modules themselves, the parts placement and how to shrink down everything so it fits in the case that you have. Along the way you might think about circuit interaction and unwanted feedback paths.

 

Buying a kit is all about not maxing out your credit card and nothing else. But There are some kits that may prove interesting as a springboard into another more significant project.

 

This is a schematic of a shortwave receiver kit that tunes from 3 to 30MHz and receives AM and FM. The front panel sports an LCD Display, and the docs are all in Chinese. The IF is at 10.7 MHz and the cost is 2.5 Big Mac's at Mickey Dee's. I received this as a Christmas Present.

See if you can see the potential of adding a 10.7 MHz BFO and the possibilities as a General Coverage (useful) CW and SSB Receiver.

Scratch Building Stuff

 

I have an OCD syndrome when it comes to the building of SSB transceivers as I often am thinking about the next build and am only 70% done with the current project. 

 

One of my future quests is to build yet another smaller version of the Shirt Pocket SSB Transceiver only this time with a goal of 12 Cubic Inches. The size would be 2 X 4 X 1.5 inches.

 

Such a size screams SMD components all the way. This also means that the Power Output would be low (around 500 Milli-watts). The IF would be a four-pole filter using the short can crystals. The 4.9152 MHz IF Frequency opens the doors to either 20 or 17M. 

 

Don't scoff at 500 milli-watts as Ben Vester W3TLN (SK) built a 100 milli-watt SSB transceiver that operated off of 6VDC as he had installed it in a Pre-1966 VW Beetle (switch over year to 12 Volt Batteries). 

The QST article shows a D-104 microphone towering over the very small transceiver case. If you can call 5X7X2 as a small case. The year was 1963 so indeed a piece of advanced technology. The Final Amp was a 2N706. The 2SC5706 will do 500 Milli-watts. Tomorrow I will tell you about the Vester rig and How QST did it again.

73's

Pete N6QW

 

January 13, 2024. Just Technical Stuff. Mary Jo is not mentioned today.

The value of a Simple Project. 

Several years ago I found in my stash of parts a bag of Motorola MC1496 Double Balanced Mixers. I think I purchased a dozen from a reputable US Supplier and the cost was $6. No Alibaba stuff here.

I hit upon an idea to build an SSB transceiver using nothing but the MC1496's in all the major pieces like the Rx and Tx mixers the Balanced Modulator and the Product Detector. (4 pieces out of the 12.) The IF Stage would be built using Dual Gate MOSFET's, the 40673.

 

But I thought it might be wise to build a test circuit first to assure all of the MC1496 devices worked and perhaps cherry pick the best of the 12 for the circuit modules.

 

The DCR Board with the MC1496, 2N3904, LM380N-8
 

Underside of the DCR

What better way to test the MC1496's than to build a simple Direct Conversion Receiver using a socket to cycle the devices under test and my go to 2N3904/LM380 audio amp. 

 

While under construction I thought about an RF amp stage and wanted to try a 2N3906 PNP transistor just to piss off those who only use the 2N3904.

 

 

What resulted astonished me! Of course no Analog VFO crap so I used the Arduino/Si5351 for the LO. It was so good that I wrote an article for the GQR-P Club SPRAT on the DCR project.

 

To my surprise this project hit a nerve and I have received about 160 requests world wide for the Arduino sketch and know many of these were actually built. Along the way I got help from two UK hams who built the project and they too published data on their MC1496 project efforts. I have been told that this was one of the most popular projects published by the G-QRP Club. 

 

Just today I received an email, some several years later, that another MC1496 is inhaling RF. Of note this build used a different Audio Amp and RF Amp plus he got some benefit from his son, a software guy, who programmed his Arduino Uno.

 

So in my response back to him was that there were 4 hidden benefits to his completing the project.

 

1)  He had some fits and starts but didn't give up.

2) He learned from the ground up how the Direct Conversion Receiver worked

3) He made substitutions based on what he could find. (A different Audio Amp IC and different RF Amp.)

4) He had a real sense of accomplishment in being able to say "I built that rig".

 

I have challenged him to get his son to program the Arduino so on demand the LO signal shifts 700 hertz and with a few more inexpensive parts has a CW transceiver. 

This afternoon the UK Ham who emailed me early this morning shared a photo of his final build. He had a defunct computer switching power supply and repurposed the case into an enclosure for his DCR. Bravo and Bellissimo! 

So, you couch potato heads who never build nothing hams -- get off your butt and get started!

 

BTW I did go on to actually build that MC1496 SSB transceiver and the 40673 IF stage came from SSDRA. I shared the MC1496 project with W7ZOI and he in turn  shared that with the original builder of the IF stage. The Circle is complete.

 

 

 

73's

Pete N6QW

January 12, 2024. Back on the Old Blog

 There is some sort of Software Glitch with the hamradiogenius blog so we are restarting the old N6QW Blog.

These are just some random photos. For the blog demographic (us old farts) you will see singular technical posts and no updates (or hot women that are single) with the next entry on January 13.

WTB Anyone have an operational RK-4D32 vacuum tube they would like to send me for $10 plus postage?

It is inexplicable why the hamradiogenius blog has a software issue. But here we are and good to be home.

Here is a sample circuit for a discrete component (non-IC) two tone tester made with common parts. I would put in a 9 VDC three terminal regulator and connect this to 12 VDC. This should be in everyone's shack or maybe there is an app for this.

73's

Pete N6QW

You Can Build This!

A Rant Email!

One of my projects in 2021 was the P3ST (AKA PSSST), a 7 transistor SSB transceiver which even found its way onto "hackaday". I even spent more time documenting the project than actually building the hardware. An .io group was started (not by me) and the project has essentially died the death from lack of interest.

This morning several emails were generated from the group inquiring if the project was still alive. Essentially these were individuals of interest but who had done nothing on the project as they were overwhelmed by the documentation. My read was that someone wanted a kit where they could stuff parts on a board. But in reality, I realized I failed! 

Here was my response. Mind you my bent is somewhat bent because the opportunities for me personally to homebrew another project are over! But for others it is not -- get on with it!

Hi All,

 

I should confess that I spent more time documenting the P3ST than actually building the rig. My intent was to provide information to those who are not EE’s but have a love for our hobby. I now sense that I have failed. I know of about a half of dozen that are in various stages of construction and a rarity I have received no “your design sucks” emails. That is a 1^st. But that likely is of no help or interest to the several who have posted

 

It is probably not a good idea to undertake this project if the documentation provided is not clear and aside from me building it for you (which I wouldn’t do) the information provided is about as good as it gets. Having a detailed parts list, resident BOM with the Suppliers and a circuit board while it makes it very easy, but this project was not intended as a kit

 

There was a unique concept presented (likely I failed in the presentation) that if you built the digital LO/BFO 1^st then added the two ADE-1 mixer stages followed by the Band Pass filter and microphone amp and the audio amp – that you would have a Direct conversion receiver and a Double Side Band Transmitter. Using a modular approach (all of these are really modules) you can test if these are working while enjoying the benefit of the DCR. All of my projects are experimenter’s platforms where you can make changes to a module without destroying the whole radio.

 

The Module concept lets you learn more about the innards than simply stuffing parts on a board. The Modules can be independently tested out of the circuit. So once built and tested then the module is no longer a point of failure when all connected. Yes, you would have to learn LT Spice – but isn’t that a real part of a homebrew project –learning! You learn very little stuffing parts on a circuit board.

 

There is another very major point – no Bitx, No TIA, No EMRFD or Facebook groups. It is a new design approach and proves that you can be something other than sheep in this hobby.

 

If you want a real sense of accomplishment that you actually built something while also learning about individual circuits, then the P3ST is a good starting place. But you should not undertake the project if you feel uncomfortable with the documentation. Questions about the project can be put on this forum which I am a member and would be happy to explain the methods of my madness.

 

You can build this!

 

73’s

Pete N6QW