Ham Radio did not start with Appliance Boxes ~ Neither should you! 12/14 Update
Hams have become lazy, prone to excuses and think only of buying their rigs.
Ham Radio is a technical hobby and if you are not technically inclined then think about stamp collecting! Regrettably, the ARRL has made it way too easy to get a license which means our ranks have swollen with a bunch of LIDS!
In the early days of our hobby if you couldn't scratch build your station you were out of luck! Today if you have a credit card that is not maxed out, then you can get on the air. Oh, the license thing, you just memorize 20 questions and then fill out a box top. Despicable is the operative word!
If you are a true ham radio operator, then you should be capable of doing this. It has been suggested that of the about 700K US Licensed Hams perhaps only 1% engage in homebrewing their rigs. Do the math as that is about 7000.
So, OK for the many who have no technical skills go back to your Baofeng UV35.
If you are feeling a bit guilty, then tune into this blog where we will reinvent the thrill of the way ham radio used to be. If you are offended, then just go away as you "lack the knack"!
This blog shall:
- Not present Complete Schematics
- Not furnish BOM's placed with Distributors
- Not provide Parts Lists
- Not provide PCB'S
- Not use designs featuring Glue Stick PTO's
- Perform all work in Modules using Block Diagrams
- Utilize Circuit simulation with LT Spice
- If at all possible, avoid Bitx circuits, TIA circuits, EMRFD circuits and Facebook Groups
If you can design and build circuits relying on these principles, then you can build anything!
The thrill of using a homebrew rig is better than contests which have no appreciation of what it really takes to fabricate the station rig!
Synopsis of Future Posts: Start Smart and Start Small!
12/13/2022 Posting.
Start Smart and Start Small.
There are but a handful (maybe less than you can count on one hand) of radio prodigies. Perhaps Marconi and Armstrong are on that list. Likely you could add Art Collins and in modern times K5SDR (Gerald Youngblood). They had ideas that turned into expansive product lines. Importantly these individuals were/are visionaries who actually developed the technology versus just designing circuits. They saw possibilities beyond a Michigan Mighty Mite or a Pixie Radio Transceiver.
Guys like DeMaw and Hayward are top drawer engineers and exemplify their skills that finds their designs in many homebrew radios. You could also add Farhan and Hans Summers. Likely these individuals did not start out on day one with "I am going to build a TIA amp or today I will design a Bitx radio" instead they had to learn about electronics, circuit theory, and lest I forget a lot of cut and try. From there they built upon their knowledge base. This is where we start.
Do Not go out and buy EMRFD as a 1st book. You may eventually want one as it makes an excellent book end or door stop. Forget the ARRL Handbook as it is nothing more than a fat catalog of Far East radio products disguised as a technical book. The very best first books are from Hayward/DeMaw and that includes Solid State Design for the Radio Amateur. It is worth its weight in gold. I have literally built ALL of the radios in that book including the Competition Grade CW Receiver at the very end.
Let me focus on the import of this book. Virtually all of the current ham hardware includes Band Pass Filters. So likely today you can go to Hans Summers shop or W8DIZ and buy the one (or several) that you would need for your project.
The other option is to find an Online Calculator and enter a few parameters and out spits a design. But the best option if you want to learn about Band Pass Filters and how the values are derived is to use the Appendix in SSDRA. Hayward steps you through the design equations so that when you are done, you have BPF that you designed. But you are not done!
The next step is to learn how to use LT Spice. Taking the values, you derived in the equations you can simulate the circuit. The BPF is the heart of many ham radio homebrew rigs.
Time to bash the Nano VNA. A ham was building one of my projects and subjected his build to his newly acquired Nano VNA. He starts out by saying what is wrong with your design as the curve had two humps and not flat across the band pass.
Because I have scratch designed BPF's and have simulated them in LT Spice, I immediately knew the problem and it was the section coupling cap. If the value of this cap is too large or too small you will either get a very narrow pointed response or one with two humps. I told him to check that cap.
He had used the wrong value and once fixed got the proper shape of curve. His Nano VNA did not tell him the answer as it only reflected the condition. But by scratch creating the design and using LT Spice you can see the effects of changing the values of the small coupling cap. Hayward in the appendix shows you how to build really small value coupling caps -- your Nano VNA will not tell you that.
A place to start is by acquiring SSDRA and hand designing a Band Pass Filter and then proceed to testing that filter in LT Spice. Eventually our journey will take us to impedance matching and once again LT Spice will be the tool to look at the effects of a mismatch.
The 1.5 PF section coupling Cap can be a Trimmer or two 3 PF in series
A 17M BPF
17M BPF Plot
The learning is what counts when your homebrew rig is inoperative. Unfortunately, our appliance ops have only one option -- send the radio back to the manufacturer. But that is by design (from the manufacturers) as now that op has to have two radios to stay on the air. One radio is always with the manufacturer -- even to replace a light bulb on the front panel!
A story from an unrelated field. Boeing is finishing the fabrication of the very last 747 aircraft which will be delivered in 2023. Close to 1600 units have been built over a 54-year period. But production will soon be over. I was a witness to when ship #1 was going down the assembly line. Typically ship #1 is a Flight Test aircraft and is never sold to a customer -- it will get pretty beat up!
In early 1968 as ship #1 was in final assembly an accident occurred where the aircraft slipped off the jacks and a jack penetrated the lower wing skin into the fuel tank area. DISASTER with a Capital D. It was interesting to see the factory floor huddle about what to do.
The Bean counters (and management) were in Cardiac Arrest. The bright engineers simply stated cut off both wings and install a new set of wings -- that would add 2 months to the schedule. That two months from a customer perspective would be like giving your girlfriend an STD. Finally, someone in the manufacturing management chain said let's ask Bill. As it turned out Bill was my boss.
Bill had worked on the B-29 program in the manufacturing/final assembly group during WWII. So, he had a lot of tribal knowledge. He went shipside to ship #1 and started laughing. He utters "this happened all the time on the B-29 line" and here is how to fix it. His 1st comments were that it was a flight test airplane and would ultimately have lots of patches. It would also never be sold. All that would be required is to apply a patch over the puncture hole and to assure it was structurally sound.
Oh, the time loss -- 1 shift as the required time to apply the fix. Outside of the manufacturing arena about two shifts to document the issue and the corrective action, but that did not prevent the manufacturing operations from moving forward.
I share this story as it demonstrates that knowing what you are doing makes a huge difference -- 1 shift from Bill versus two months and huge costs from the engineers many of whom were infants during WWII. Building your rig from scratch gives you the knowledge and confidence to fix what you build.
The endearing motto: "Those who can't, lack the knack"!
12/14 Update
Taking Einsteins's equation E=MC^2 where some simple terms hold a deep well of knowledge is not unlike what VU2ESE (Farhan) has said about Ham Rigs. Farhan posited you only need to know 4 circuits to build a ham rig. These include Oscillators, Mixers, Amplifiers and Tuned Networks.
Oscillators could include the Local Oscillator (LO), the Beat Frequency Oscillator (BFO), and finally the High Frequency Oscillator (HFO).
Mixers could include the Receiver / Transmit Mixer stage and a special form of Mixer the Balanced Modulator stage. Of interest the ADE-1, an SMD packaged Double Balanced Mixer (DBM) will fit on your thumb nail and can do both of those tasks. Other tasks for Mixers would be in the use of Frequency Translation Conversion stages such as you would have in a double conversion transceiver.
Amplifiers are used within many stages of a rig. These include the RF Amp stage at the front end, the Intermediate Frequency Amplifier stage, as well as Amplifier stages to boost the signal from the low-level RF stages to drive the High-Power RF amp stage. Finally, we have the Audio Amplifier and Microphone Amplifier stages.
Lastly, our tuned networks are the traffic cops that steer signals into and out from our rig only on the frequencies where we want them. Crystal Filters are also Tuned Networks.
I agree with his premise and now if we focus on the general aspects of these four circuits, we can have a better feel what it takes to build a ham rig --- from scratch.
