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The NanoVNA has become one of the most popular handheld vector network analyzers among hobbyists, RF engineers, antenna builders, and experimenters. It’s compact, affordable, and surprisingly capable. But there’s one critical step that determines whether your measurements are meaningful or misleading:
Calibration
If you skip calibration—or perform it incorrectly—your NanoVNA will still display curves and numbers, but they won’t reflect the true behavior of your device under test. Before every measurement session, and especially whenever you change frequency ranges, cables, adapters, or test fixtures, you must calibrate the instrument.
This guide walks you through why calibration matters, when to do it, and how to perform a proper SOLT calibration (Short, Open, Load, Thru) on the NanoVNA.
Why Calibration Matters
A VNA doesn’t measure your antenna, filter, or cable directly. Instead, it measures the combination of:
the device under test
the test cables
the connectors
internal imperfections
frequency response of the instrument
stray capacitances and inductances
Calibration mathematically removes these unwanted influences so the NanoVNA can isolate the behavior of the device you actually care about.
Without calibration, you may see:
incorrect SWR
shifted resonance points
wrong impedance values
misleading return loss
distorted S‑parameter curves
Even a high‑end lab VNA requires calibration. The NanoVNA is no different.
When You Should Recalibrate
You should calibrate every time you:
change the frequency sweep range
swap cables or adapters
move the NanoVNA to a different environment
measure a different type of device (antenna vs. filter vs. cable)
haven’t calibrated in a while
A good rule of thumb:
If anything in the signal path changes, recalibrate.
What You Need
Your NanoVNA should come with a calibration kit containing:
Open standard
Short standard
50‑ohm Load
Thru (usually just a male‑to‑male or female‑to‑female adapter)
If you have upgraded to higher‑quality calibration standards, even better.
Step-by-Step: How to Calibrate the NanoVNA (SOLT Method)
The NanoVNA uses the industry‑standard SOLT calibration: Short, Open, Load, Thru.
Below is the full procedure.
1. Set Your Frequency Range First
Calibration is frequency‑dependent. Set your sweep range before calibrating.
Example:
Antenna work: 50–600 MHz
HF: 1–30 MHz
Filters: narrow ranges around the passband
On the NanoVNA:
Menu → Stimulus → Start / Stop
2. Connect Nothing to Port 1 (CH0)
This is your reference port.
3. Perform the OPEN Calibration
Attach the Open standard to Port 1.
On the NanoVNA:
Menu → Cal → Open
Wait for the sweep to complete.
4. Perform the SHORT Calibration
Remove the Open, attach the Short standard.
Menu → Cal → Short
5. Perform the LOAD Calibration
Attach the 50‑ohm Load.
Menu → Cal → Load
This step is crucial for accurate impedance and SWR readings.
6. Perform the THRU Calibration (for S21 / CH1)
If you plan to measure filters, cables, or transmission characteristics, you must calibrate the second port.
Connect Port 1 to Port 2 using the Thru adapter or a short coax jumper.
Menu → Cal → Thru
If you only measure antennas (S11), you can skip this step.
7. Save the Calibration
Once all steps are complete:
Menu → Cal → Save → Slot 0–4
You can store multiple calibrations for different frequency ranges.
8. Verify the Calibration
A quick sanity check:
Attach the 50‑ohm load
SWR should read very close to 1.0
Impedance should be near 50 + j0 Ω
If not, repeat the process.
Tips for Better Accuracy
Use high‑quality coax jumpers
Avoid touching connectors during calibration
Keep the calibration standards clean
Use torque‑controlled tightening if possible
Keep the NanoVNA stable during the sweep
Avoid cheap adapters that introduce reflections
Small details matter when you’re working at RF.
Why Calibration Before Measurement Is Non‑Negotiable
The NanoVNA is incredibly capable, but it is only as accurate as its calibration. A poorly calibrated VNA can easily mislead you into:
cutting an antenna to the wrong length
misdiagnosing a cable fault
misunderstanding a filter’s passband
thinking a device is mismatched when it isn’t
Calibration is not optional. It is the foundation of every meaningful measurement.
Final Thoughts
Calibrating the NanoVNA may feel like an extra step, but it’s the difference between guesswork and real RF insight. Once you build the habit, it becomes second nature—and your measurements will be dramatically more reliable.
If you don’t already have one … treat yourself to the NanoVNA .
I used mine to test my v2 20-meter band-pass filter here.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
AI is powerful — but it performs at its best when you give it context. That one word, context, is the difference between a vague answer and a useful one. I love analogies, so let me start with a story that perfectly illustrates how AI works, why it sometimes gets confused, and how a little backstory can completely change the outcome.
I have a lot of interests. My wife never knows what topic I’m going to jump into next. Add a splash of ADD and maybe a dab of autism, and you’ve got a recipe for delightful chaos. One minute I’m talking about antennas, the next minute I’m redesigning a circuit board, and somewhere in between I’m wondering where I left my digital calipers. Humor aside, this unpredictability is exactly what happens when people interact with AI without giving the backstory. When context is missing, the conversation feels scattered — and the results can be just as confusing.
Here’s the first thing I want folks to understand: AI is not Google. Search engines look for keywords; AI looks for understanding. Most people still type prompts like search queries, then wonder why the answer feels incomplete. The truth is simple — AI needs context to deliver meaningful, accurate, and helpful responses.
Sharing My Experience Via Context
I use AI every single day — for work, for hobbies, and for some very technical challenges. I’ve experimented with multiple AI platforms and models, and even when using highly capable systems, I’ve learned that they still need strong context. Sometimes the AI gets things wrong, but more often than not, it’s just doing the best it can with the context it was given. When I improve the context, the answers improve. It’s that straightforward.
Let me ground this in something real. I’m building a seven-band HF SSB transceiver — a HAM radio designed to communicate across the globe. My background is in electrical engineering with a heavy focus on digital systems and assembly language. Communications theory? We touched it, but building an entire HF transceiver from scratch is a different level of complexity. That’s where AI became my technical co-pilot.
At the beginning of this journey, my questions were broad. I’d ask something like, “How do I design a mixer stage?” and the answers were generic. Once I started adding backstory — my frequency range, my architecture, my available components, my goals for stability and cost — everything changed. The AI moved from giving textbook answers to giving practical guidance that matched my actual project. Same AI, different context, dramatically better results.
As a licensed HAM, I passed exams that covered electronics fundamentals, but not to the depth required to design an entire transceiver. AI has helped me bridge that gap by turning curiosity into structured learning. Sometimes it even answers questions I didn’t know how to ask — because the surrounding context helps it anticipate what I’m really trying to achieve. And when it makes a mistake? I challenge it. I provide more context. I say, “Nope, that doesn’t fit this design,” and suddenly the next answer aligns much closer with reality.
Think about it this way. If I ask my wife, “Honey, have you seen my digital calipers?” she might give me a blank stare because the context is missing. But if I say, “Honey, I’m trying to measure the distance between clips on my PCB so I can build an RFI enclosure — have you seen that silver measuring tool with the digital readout?” she instantly understands the context and points me to the dining room table… along with a reminder that it belongs in the garage. Same question, more background, completely different outcome.
That’s exactly how AI works. Context unlocks clarity. Context shapes relevance. Context reduces guesswork.
My goal here isn’t just to help you find your car keys or troubleshoot a circuit. My goal is to help you understand how to think when you interact with AI. The old saying still applies: “Garbage in, garbage out.” But today I’d rephrase it slightly — “Weak context in, weak results out.” When you give AI richer context, you’re not just asking a question; you’re building a shared understanding that leads to better collaboration.
Some people worry that AI will replace them. I don’t see it that way. AI is a tool — a very powerful hammer — but without context, every problem still looks like a nail. The real advantage belongs to the people who learn how to use context effectively. They’re the ones who get clearer answers, faster solutions, and deeper insights.
So here’s my elevator pitch: If you want better results from AI, don’t just ask questions — give context. Explain what you’re doing, why you’re doing it, what you’ve already tried, and where you’re stuck. Treat AI less like a search bar and more like a collaborator who needs backstory to help you succeed.
Because at the end of the day, you’re not going to be replaced by AI. You’re going to be replaced by someone who knows how to use AI with the right context — and knows how to swing that new hammer with confidence.
Try it. Use it. Tell it it’s wrong. My two favorites, Copilot and ChatGPT.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
A not-so-linear approach to creating a quality low noise amplifier for my HF transceiver.
I am very aware of AI, what it can do, how it works, and how it can let you down. I use it daily as an assistant as a professional IT architect. I took electrical engineering in college but my emphasis was digital logic and microprocessors. As an amateur radio operator, I have a great interest in how all these radios actually work. Some understanding is gained by study for the FCC license exams. I’m currently a General (second-level) operator. I am however, studying for my Extra (highest-level) license. This ticket allows more areas of the band spectrum that are off-limits to the lower-level licensees. Recently I’ve gained a lot of my detailed HF understanding using Microsoft Copilot’s AI during the design of components for my DIY HF transceiver the Freedom7.
I will take the reader through my design process here now and also share that I’ve already done this with failures. This is the not-so-linear aspect I referred to in my subtitle above. I’m currently working on a 20 meter band-pass filter for the second time. This post will describe my low noise amplifier (LNA) that comes after the band pass filters in the receive chain. The LNA is shown in the diagram below.
I have already designed switching mechanisms for 7 band-pass filters, for 10, 15, 17, 20, 40, 80, and 160 meters that are not shown in this diagram, but it shows the need for amplification after the passive band-pass filter to provide a serviceable signal at the mixer.
I designed this LNA already and I’ve even modeled it using LTSpice. I have a schematic in KiCAD but I left it and moved to LTSpice because I wasn’t satisfied with the design and wanted to model it’s behavior and understand it’s performance. Currently the best design that I have can be shared with the reader via the schematic in LTSpice.
To add to my not-so-linear wording in my subtitle, I’ll describe another failure (lesson-learned?) at this point in my design process here. I have a nice box with a wide range of ceramic capacitors and also electrolytics. I also have a cheap box of radial inductors with a wide selection of values. I modeled this on a breadboard. I think C3a should be an electrolytic (not shown). I broke out the 12v power supply, fired up the signal generator, and connected a 50 ohm connector to my oscilloscope. I expected beautiful results. Oh, how I was wrong!
With the help of Microsoft’s Copilot, I’m now going to explain this failure and the newfound education I’ve acquired.
When My 1–30 MHz LNA Met a Breadboard: A Cautionary Tale
Designing the LNA on paper felt elegant. Simulating it felt even better. Then I built it on a solderless breadboard — and everything fell apart. The amplifier oscillated, detuned itself, picked up every stray signal in the room, and generally behaved like it had a personal grudge against me.
So what happened? The short answer: breadboards and RF don’t mix. The long answer is much more interesting.
A solderless breadboard looks electrically simple, but at RF it’s a jungle of unintended components.
1. Breadboards Have Enormous Parasitics
Each tie point adds 2–5 pF of stray capacitance.
Each row has tens of picofarads between adjacent rails.
Every jumper wire adds tens of nanohenries of inductance.
At audio frequencies, these parasitics are irrelevant. At 1–30 MHz, they’re circuit‑destroying.
Your carefully tuned input network suddenly becomes a random LC filter. Your bias network becomes a resonator. Your transistor sees a completely different impedance than you designed for.
2. The Ground Plane Doesn’t Exist
RF circuits need a solid, low‑impedance ground plane. Breadboards offer the opposite:
Long, thin ground rails
High inductance
No shielding
No controlled return paths
The result? Your LNA’s ground reference floats, shifts, and radiates. The amplifier starts behaving like a tiny radio transmitter — and a very bad one.
3. Oscillation Becomes Almost Guaranteed
Wideband LNAs are inherently sensitive. They need:
Short leads
Tight layout
Controlled impedance
Proper decoupling
A breadboard gives you:
Long leads
Random layout
Undefined impedance
Decoupling capacitors connected through inductive rails
This is the perfect recipe for VHF oscillation, even if your design is only meant for HF. Many LNAs will happily oscillate at 80–200 MHz if you give them the chance — and a breadboard gives them every chance.
4. The Breadboard Acts Like an Antenna Farm
Every jumper wire is an antenna. Every row is a transmission line. Every gap is a slot radiator.
Your LNA ends up amplifying:
Local AM broadcast stations
Switching noise
Your laptop’s USB emissions
The fluorescent lights
The neighbor’s lawnmower ignition noise
Instead of a clean 1–30 MHz signal, you get a chaotic RF soup.
5. Power Supply Noise Goes Straight Into the Amplifier
Breadboards provide almost no isolation between:
Power rails
Signal rails
Ground returns
Even a clean bench supply becomes noisy once it hits the breadboard. Your LNA sees that noise as input signal and amplifies it gleefully.
The Takeaway
The LNA design wasn’t the problem — the construction method was. Breadboards are fantastic for digital logic, microcontrollers, and low‑frequency analog. But for RF, especially wideband RF, they’re essentially parasitic component generators.
If you want an LNA to behave, you need:
A copper‑clad ground plane
Short, direct connections
Proper shielding
SMD components if possible
A PCB or at least “Manhattan style” construction
My LNA didn’t fail because the design was bad — it failed because I built a precision RF amplifier on a device that’s basically a parasitic capacitor farm. Lesson learned: breadboards and megahertz don’t mix.
Decisions, Decisions: A Story to Explain
At this point in the LNA design process, do I proceed with the PCB manufacture? Do I add Harwin RFI shielding clip pads to the PCB? Am I really ready to pull the trigger on the PCB design using the schematic I’ll update in KiCAD from LTSpice?
My decision was to go through deep discussion with AI today and write this blog post, now describing my design of the LNA schematic in great detail. My post is aptly titled “Revolutionary New Design Process Includes AI” and while I want to re-validate my design, I’m going to provide the guidance I was originally given here in this post. This was more than just guidance, it was education. It really enlightened my understanding of the overall design process.
Designing a Low Noise Amplifier for HF: A Story to Sell Teamwork
I am certainly humbled by the power of AI and as a manager of people, I know the value of teamwork. I’m going to show the reader the value of using AI to answer all of the hard questions. At this point in time, my goal is to design an LNA for my HF radio that just works. My goal is described as follows:
Amplify very weak RF signals from the antenna with:
Low noise figure (NF)
Reasonable gain (10–20 dB is typical at HF)
Good input/output matching (usually 50 Ω)
Stability (no oscillations, no weird behavior with strong signals)
Linearity (doesn’t distort when a strong nearby signal appears)
At HF, the first active device largely sets the receiver’s noise performance. Everything I do in this stage—biasing, matching, layout—will feed into that.
My device has already been chosen. I have a supply of BFR93A SMD bipolar junction transistors on-hand. I think of this transistor as a transconductance device: input voltage → output current, then a load resistor/transformer turns that into voltage gain, hence the term amplifier. My LNA amplifies AC or RF signal input.
DC Bias
First and most importantly, I need to set the operating point of the transistor or amplifying device with DC bias. The transistor must sit at a quiescent point (Q‑point) where:
It’s in the region where noise performance is good
It’s in Class A (conducts over the full RF cycle)
It has enough headroom for signal swing
I would typically set:
Collector current : often 1–10 mA for HF LNA
Collector voltage : maybe half the supply (e.g., 6 V on a 12 V supply)
Base bias via a resistor divider or current source
Basic idea:
Choose for a good trade‑off between noise, gain, and power
Use a collector resistor such that:
Base bias network sets
Emitter Bypassing
In a Bipolar Junction Transistor (BJT) amplifier, the emitter resistor sets the transistor’s bias and stabilizes the gain. That resistor also introduces negative feedback, which keeps the amplifier linear and predictable, specifically needed for this sensitive amplifier.
But there’s a catch.
Negative feedback reduces gain — including the gain you want at RF.
Emitter bypassing is the technique of placing a capacitor in parallel with the emitter resistor so that:
DC still sees the resistor (for stable bias)
AC/RF sees the capacitor (which looks like a short at RF)
In other words:
The resistor controls the transistor at DC. The capacitor “turns off” the resistor at RF so you get more gain. See the balance here?
If you return to my schematic, I have 3 components here, R4, C3a, and C3b. My 10uF capacitor, C3a is electrolytic as a choice because it’s suited for the low frequency short.
Emitter bypassing is powerful, but it comes with trade‑offs. The emitter resistor provides negative feedback that helps prevent oscillation but by bypassing it, you remove that feedback at RF, reducing stability. This design choice affects all that bad stuff I talked about above. I’ll have the option of changing values on my PCB using SMD packaging when I’m at that point.
I’ll wrap up this section with my best explanation. In a low‑noise amplifier, the emitter resistor sets the transistor’s bias and keeps the circuit stable, but it also reduces gain and adds noise. By placing a capacitor across that resistor, we “bypass” it at RF frequencies. The transistor still sees the resistor at DC, so the bias stays stable, but at RF the capacitor looks like a short, restoring gain and improving the noise figure. The trade‑off is that bypassing removes some of the stabilizing feedback, so layout and grounding become more critical to prevent oscillation.
Input and Output AC Coupling
As RF is the signal we’re processing we need input and output AC coupling at both ends of the amplifier. We will use capacitors to handle this job. The input capacitor will block DC so that our biasing is unaffected. It will also pass our RF with proper reactance, really around 50 ohms at the lowest frequency of the amplifier’s bandwidth. I choose its value so its reactance at the lowest frequency of interest is small compared to 50 Ω:
For example, at 1.8 MHz, you might want , so in the hundreds of pF to a few nF. I think it’s currently 100nF and that’s subject to change. Again, notice the not-so-linear approach to all this.
The output coupling capacitor needs to do the same. Its value was chosen so its reactance is small at the lowest frequency of interest and it blocks DC from the collector/drain. It will pass RF to the next stage, the mixer.
Impedance Matching
Now we’re seriously going into uncharted territory. It’s also where this RF stuff seems like an art in itself. I want to start with the input matching. I want the source (antenna and passive filter, usually 50 Ω) to see a good match into the LNA input.
Input Match
But the transistor’s input impedance is not 50 Ω by default. It’s some complex value depending on:
Bias point
Device parameters (gm, β, capacitances)
Frequency
Realize at this point, we’ll interject a change between the true input and the transistor device. I would use a matching network:
L‑network (series L, shunt C or vice versa)
Transformer (turns ratio to transform 50 Ω to the desired impedance)
Tapped inductor or autotransformer
Band‑pass network (for selectivity + matching)
I’ll use an LC network because I already have a coupling capacitor that can partner in a series LC situation to give us the impedance close to 50 ohms.
Copilot AI helped me realize there’s no perfect solution here and this is yet another piece of the LNA puzzle that may need some trial and error component value changes. The impedance that gives minimum noise figure is often not the same as the impedance that gives maximum gain for the amplifier.
So one would choose a source impedance (via matching network) that:
Is close to the optimum noise impedance of the transistor at that frequency
Still gives enough gain and reasonable match
This is one of the core design tensions in an LNA. And, I need to get the datasheet and review my current schematic before I can give it final approval.
Output Match
In keeping with the broadband 1-30MHz concept, we can’t use any form of LC combo. And, as I’m writing this .. . I gave AI this prompt: “Now, I’m questioning a 100nF, 47uH LC series input matching combo.” It seems that my design for the AC coupling was satisfactory but the LC combo to get the impedance matching is off.
Not-so-linear is becoming my mantra. I have conveyed my methods and how I use AI to answer my questions and then I tailor more questions as AI educates me. And, I have found errors in my design at this point and I have not finished the full outline of the LNA design aspects.
Conclusions
I’m going to conclude the details here but I am going to share an outline of how this should go when the final design is solidified. If I write about “every aspect” of my HF LNA, a nice structure might be:
Measured vs. simulated performance (gain, NF, IP3, stability)
System role of the LNA in an HF receiver
Choosing the transistor and topology
DC bias design (with example calculations)
AC small‑signal model and gain derivation
Input and output matching (with Smith chart examples if you like)
Noise figure and how design choices affect it
Stability analysis and practical stabilization tricks
Power supply decoupling and RF chokes
Layout and construction details (lead length, shielding, grounding)
I tend to think that I will use this outline and write about each when my not-so-linear approach at this LNA is complete.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
For years, surface‑mount devices (SMD) carried a reputation for being “too small,” “too fiddly,” or “only for factories.” Many Makers, HAM radio tinkerers, and DIY electronics hobbyists stuck with through‑hole parts because they felt safer and more familiar.
But the truth is this: with a little practice, a bit of flux, some liquid solder, and an inexpensive rework station, SMD work becomes not only approachable—it becomes fun. Once you learn the technique, you’ll wonder why you avoided it for so long.
This article is an invitation to give SMD a chance. You don’t need a professional lab. You don’t need a microscope. You don’t need a thousand‑dollar hot‑air station. You just need curiosity, a steady hand, and the willingness to try something new. I also use these glasses too. $20 on Amazon Yoctosun Magnifying Glasses with LED and headband
Why SMD Is Worth Learning
SMD components offer real advantages for home projects, especially as electronics continue to shrink and more parts become surface‑mount only.
1. SMD Saves Space—A Lot of It
Through‑hole components take up board area on both sides and require long traces to reach their pads. SMD parts sit flat on the board, allowing:
Smaller PCBs
Cleaner layouts
Shorter signal paths
More room for connectors, inductors, relays, and other bulky parts
In HF radio projects, this matters. You can reserve precious board space for the components that must be through‑hole—like toroids, high‑power RF transistors, or large electrolytic capacitors—while using SMD for everything else.
2. Many Modern Components Are SMD‑Only
If you want access to the latest ICs, filters, op‑amps, microcontrollers, and RF modules, SMD is often the only option. Learning SMD opens the door to:
Better performance parts
Lower noise amplifiers
Modern RF front‑end chips
Compact voltage regulators
High‑quality ceramic capacitors
You’re no longer limited to whatever through‑hole parts are left in the catalog.
3. SMD Can Actually Be Easier to Solder
This surprises people, but it’s true.
With through‑hole parts, you often fight with:
Leads that don’t fit
Pads that lift
Components that fall out while flipping the board
Excessive heat needed for large pins or ground planes
SMD, on the other hand, rewards technique over brute force. With flux and liquid solder, the surface tension does most of the work for you. Pads pull the solder into place. Components self‑align. Mistakes are easy to fix with hot air.
4. Rework Is Faster and Cleaner
A cheap hot‑air rework station can remove surface mounted ICs in seconds. Try doing that with a 40‑pin DIP without damaging the board.
For prototyping and experimenting, SMD is incredibly forgiving.
What You Actually Need to Get Started
You don’t need a professional setup. A beginner‑friendly bench can be built for less than the cost of a single high‑end soldering iron.
Here’s a realistic starter kit:
A basic hot‑air rework station (the inexpensive ones work fine)
A small‑tip soldering iron
Liquid solder (solder paste or low‑melt solder works great)
Good flux (this is the real secret weapon)
Tweezers
A magnifier or cheap USB microscope (optional but helpful)
Remember my glasses above
That’s it. No ovens, no fancy stencils, no industrial equipment.
Where Surface-Mount Fits in HF Radio Projects
HF radio designs often mix SMD and through‑hole parts. Not everything belongs has to be surface mounted, and that’s perfectly fine.
Great Candidates for SMD in HF Projects
Bypass and decoupling capacitors
Op‑amps and low‑noise amplifiers
Filters and matching networks
Microcontrollers and logic ICs
Voltage regulators
Small RF transistors
Resistors and small inductors
These parts benefit from short leads, low parasitics, and compact placement.
Better Left as Through‑Hole
Toroids and large inductors
High‑power RF finals
Large electrolytic capacitors
Connectors and mechanical components
Heat‑dissipating devices that need bolted heatsinks
Using SMD where it makes sense frees up board space for the components that must be larger or mechanically robust.
The Learning Curve Is Real—But Short
Your first few attempts may feel awkward. Components may fly off your tweezers. You might bridge a few pads. You might overheat a resistor or two.
But then something clicks.
You learn how much flux is “just right.” You learn how solder paste behaves under heat. You learn how to nudge a part into place and let surface tension finish the job.
And suddenly, SMD stops being scary and starts being empowering.
Why You Should Try SMD on Your Next Project
If you’re a Maker, a HAM, or a DIY electronics enthusiast, SMD opens up a world of possibilities:
Smaller, cleaner, more professional‑looking boards
Access to modern components
Faster assembly and rework
Better RF performance
More efficient use of PCB space
Most importantly, it expands what you can build at home.
SMD isn’t just for factories anymore. It’s for anyone with a soldering iron, a bit of patience, and the desire to push their skills forward.
Give it a try. You might discover that the “tiny parts” are not the enemy—they’re the gateway to better, more capable homebrew electronics.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
Designing a professional two‑layer printed circuit board (PCB) doesn’t require expensive software or specialized equipment. KiCad, a free and open‑source EDA suite, gives hobbyists, students, and engineers everything they need to take a fully annotated schematic and turn it into a fabrication‑ready PCB design.
This guide walks through the complete process—from schematic capture to Gerber export—using KiCad’s modern toolset. Whether you’re designing your first board or refining your workflow, this article will help you understand each step and why it matters.
1. Start With a Fully Annotated Schematic
A clean schematic is the foundation of a clean PCB. Before moving into layout, make sure your schematic is:
Fully annotated (every component has a unique reference designator)
Electrically validated using KiCad’s ERC (Electrical Rules Check)
Organized with clear signal flow and labels
Complete with footprints assigned to every symbol
Run ERC
In the Schematic Editor:
Click Inspect → Electrical Rules Checker
Resolve warnings and errors
Confirm all symbols have footprints assigned
If you skip this step, you’ll fight errors later during layout.
2. Assign Footprints to Every Component
KiCad separates symbols (schematic) from footprints (physical layout). This gives you flexibility, but it also means you must assign footprints before generating a PCB.
Open the Footprint Assignment Tool:
Tools → Assign Footprints
Select each component and choose the correct footprint from KiCad’s libraries or your own custom library
Tips for footprint selection:
Match package size to your assembly method (hand soldering vs. reflow)
Check pad pitch and orientation
Verify 3D models if you plan to render the board
3. Generate the Netlist and Open PCB Editor
Once your schematic is complete:
Click Update PCB from Schematic
Choose “Re-associate footprints by reference”
Import the netlist into the PCB Editor
You’ll now see all your footprints “ratsnested” together, ready for placement.
4. Define Your Board Outline
Before placing components, define the physical shape of your PCB.
In the PCB Editor:
Switch to the Edge.Cuts layer
Use the Line or Arc tools to draw your board outline
Keep it simple unless your enclosure requires a custom shape
A clear outline helps you visualize placement and routing constraints.
5. Place Components Strategically
Component placement is where engineering meets art. Good placement reduces routing complexity and improves signal integrity.
General placement guidelines:
Start with connectors, switches, and mounting holes
Place ICs and major components next
Group related components (e.g., decoupling capacitors near IC power pins)
Keep analog and digital sections separated
Maintain short, direct paths for high‑speed or sensitive signals
Use the Move (M) and Rotate (R) shortcuts to speed up placement.
6. Set Up Design Rules
Professional PCB fabrication requires proper design rules. KiCad lets you define:
Trace width
Clearance
Via size
Copper zone settings
Net‑specific rules (e.g., power nets with thicker traces)
Open Board Setup → Design Rules and configure according to your PCB manufacturer’s capabilities.
Common starting values for a two‑layer board:
Trace width: 0.25 mm (10 mil)
Clearance: 0.2 mm (8 mil)
Via drill: 0.3 mm
Via diameter: 0.6 mm
7. Route the Board
Routing is where your schematic becomes a real, manufacturable design.
Routing tips:
Use short, direct traces for critical nets
Keep power and ground traces wide
Use 45° angles for cleaner routing
Avoid unnecessary vias
Route differential pairs together (if applicable)
Keep analog traces away from noisy digital lines
Use Interactive Router (X) for manual routing. KiCad’s push‑and‑shove router is excellent for tight layouts.
8. Add Copper Pours (Ground and Power Planes)
Copper pours help with:
Noise reduction
Heat dissipation
Cleaner routing
Lower impedance ground paths
To add a ground plane:
Select the Add Filled Zone tool
Choose GND as the net
Draw a polygon around the board
Press B to refill zones
Repeat for power nets if needed.
9. Add Silkscreen, Labels, and Final Touches
A professional PCB includes clear labeling:
Component reference designators
Pin 1 indicators
Board name and revision
Logo or manufacturer info
Test points
Use the F.SilkS and B.SilkS layers for silkscreen text.
10. Run DRC (Design Rules Check)
Before exporting fabrication files:
Click Inspect → Design Rules Checker
Fix any clearance, unconnected net, or footprint issues
Refill copper zones and re‑run DRC until clean
A clean DRC is essential for a successful fabrication run.
11. Generate Gerbers and Drill Files
Fabricators require:
Gerber files for each copper and silkscreen layer
Drill files
A board outline
A fabrication drawing (optional but helpful)
In PCB Editor:
File → Plot
Select Gerber
Choose layers:
F.Cu
B.Cu
F.SilkS
B.SilkS
F.Mask
B.Mask
Edge.Cuts
Click Plot
Click Generate Drill Files
Zip the output and upload it to your PCB manufacturer.
Conclusion
KiCad makes it possible for anyone—from hobbyists to professionals—to design high‑quality, two‑layer PCBs without expensive tools. By following a structured workflow from schematic to Gerber files, you can produce boards that are clean, reliable, and ready for fabrication.
Once you’ve mastered this process, you can explore more advanced features like:
4‑layer boards
High‑speed design rules
Custom footprints
3D rendering and enclosure integration
Automated BOM and pick‑and‑place files
KiCad continues to evolve, and each release brings more power to open‑source hardware design.
Please go visit KiCAD at https://www.kicad.org/ . I think you’ll be pleasantly surprised by this free software.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
AI is going to help me be a true success! While a large part of the population is afraid that AI is going to take their job, I remember a statement from Tony Robbins, the Self-Help, Success-Guy, “you are not going to lose your job to AI, you are going to lose your job to someone that knows how to use AI.”
Here’s my prompt (what I ask AI) today. “I’ve chosen components and calculated resonances, etc. for a 20 meter band pass filter using SMD components, air-core inductors (Coilcraft), and 0805 high-Q capacitors with female SMA connectors on the ends. Can you talk to me about things to consider as I design my PCB board to be really compact and use RFI shielding clips for an aluminum enclosure? Anything that I should focus on specifically?”
And, here’s the response. Remember, it’s mine to use, author, etc.
You’re in a really fun part of the project now — the physics starts to show up in the copper. Let’s talk specifically about what matters for a compact 20 m BPF PCB inside a shielded aluminum can.
1. Board stackup and grounding
This is the most important foundation.
Solid ground plane:
Use a continuous ground plane on the layer directly under the filter components.
Don’t route signals in that ground layer under the filter if you can avoid it.
Short return paths:
Every cap/inductor junction should have a very short path to ground (via right next to the pad).
For shunt capacitors, put the via as close as manufacturable (0.2–0.5 mm away).
Many ground vias:
Stitch ground around the filter area (via fence along the edges and around the SMA footprints).
Aim for via spacing on the order of a few mm in the RF path region.
The idea: the filter lives in a “RF cavity” defined by the ground plane and the metal lid; your PCB layout is the boundary condition.
2. Signal routing and physical layout
At 14 MHz, you’re not in microwave territory, but layout still matters a lot for coupling and stability.
Keep the filter linear and symmetrical:
Lay out the network in a straight line: SMA → series L → shunt C → series L → shunt C … → SMA.
Avoid dog‑legs and wildly asymmetrical element placement.
Keep traces short but sane:
Use short, reasonably wide traces between components (you’re roughly in 50 Ω land, but not truly transmission‑line dominated at 14 MHz).
Don’t obsess over exact 50 Ω microstrip, but avoid long skinny runs.
Minimize parallelism:
Don’t run input and output traces closely parallel — route them in a way that minimizes direct capacitive coupling (no “looping back” alongside each other).
Inductor orientation:
Rotate adjacent air‑core inductors 90° to each other wherever possible.
Maximize physical distance between inductors that aren’t meant to couple; even a few extra mm helps.
You’re trying to preserve the intended L/C coupling and avoid creating a mystery extra coupling path that changes your filter shape.
3. SMA connector integration
Female SMAs on a compact board inside a shield can get tricky mechanically.
Grounding the connectors:
Ensure the SMA’s ground tabs or edge‑mount ground are well tied into the ground plane with multiple vias right at the connector.
Don’t rely on just the mechanical tab; stitch it with vias all around.
Mechanical registration with enclosure:
Think in 3D: where the SMAs sit relative to the enclosure wall or hole.
Make sure there’s enough clearance so the cable can mate without pushing the PCB or stressing solder joints.
Shield continuity at the connector:
Ideally, the SMA body and the enclosure are at the same RF ground potential.
If the SMA isn’t panel‑mounted but just pokes through a hole, you may want extra ground fingers or copper pads near that opening.
4. RFI shielding clips and aluminum enclosure
With PCB‑mount shield clips + aluminum lid/box, some specifics matter.
Placing the clips:
Put clips on grounded copper regions, not over signal traces.
Use ground via stitching under/near the clip pads so each clip connection has a low‑impedance path to the main ground plane.
Shield “wall” on the PCB:
Run a ground copper ring around the filter area inside where the shield will sit.
Stitch that ring with vias to the ground plane (this becomes your RF “gasket” under the lid).
Gap control:
Try to avoid large gaps between the lid and the PCB copper ring. Even at HF it’s not critical, but better contact = less chance of weird coupling.
Aluminum is not solderable:
Your electrical connection is via the clips to a copper pad, not the lid itself.
Ensure that the lid or box is mechanically pressed against those clips or edges so there’s real metal‑to‑metal contact.
If your board sits inside a larger aluminum box, you can use both the PCB shield can and the external box as nested shielding — very effective.
5. Compactness vs coupling
When you shrink everything, coupling wants to creep in; this is where most “mystery behavior” comes from.
Watch in/out isolation:
Keep input and output physically separated by the filter network and some ground copper.
Don’t let the SMA inputs “see” each other over the top of the filter via stray capacitance.
Use ground “fences” between sections:
You can place thin grounded copper strips between sections of the filter (with vias), acting as mini bulkheads.
Guard traces:
Put grounded copper between sensitive nodes if you’re worried about coupling — especially between input and output ends.
Compact is good, but don’t make it so compact that inductors and traces are stacked over each other.
6. Practical tuning/debugging considerations
Even with careful calculation, the real PCB will need a little love.
Leave some tuning flexibility:
Use parallel pads so you can add or change capacitors (e.g., room for small parallel trimmers or extra 0805s).
Make it easy to snip out an inductor turn or stretch/compress them if you ever go custom‑wound later.
Test points:
At minimum, expose input and output SMA and make sure you can easily connect a VNA or sig gen + power meter without contortions.
Ground test pad:
Provide a good ground pad near the filter for probing, not just the SMA body.
This lets you actually see how your layout choices affected the filter response — and refine future versions.
7. Specific “watch this” items for your setup
Given what you described (SMD, Coilcraft air‑cores, 0805 high‑Q, shield clips, aluminum box):
Air‑core inductors:
Keep them slightly away from the enclosure walls and lid; very close metal will change inductance and Q.
High‑Q capacitors:
Great choice. Just keep their leads short and put ground vias right beside shunt cap grounds.
Aluminum box:
Plan screw locations or standoffs so the PCB ground has several solid mechanical + electrical bonds to the box.
Avoid routing high‑impedance nodes right under screw heads or standoffs.
If you’d like, describe (or sketch verbally) your basic layout: SMA on each end, number of poles, and board size target. I can then walk through a more concrete “place this here, avoid this there” pass tailored to your exact filter.
It’s me again! That’s quite some education there. Go learn AI.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
I started my band-pass designs using the Chebyshev model. I didn’t do my homework. I just found a schematic, chose some values based on someone else’s design using toroids, and totally ignored the “Q” values of components. I built 7 filters and also tested them on a NanoVNA. I didn’t think anything of the 3 or greater dB insertion loss. I was verifying the passband graph shape. Everything looked good. It was not. I’ve been doing lots of homework and here’s some of it.
When you design a 3‑pole Butterworth series‑coupled band‑pass filter, one of the first surprises is that the parallel LC tanks don’t resonate at the same frequency as the filter’s actual passband center. For example, you might calculate:
Tank resonance: 14.029 MHz
Filter center frequency: 14.2 MHz
At first glance, this looks contradictory. Why would the tanks be tuned below the desired center frequency?
The answer is simple once you understand how coupled resonators behave.
1. The tanks have a “free” resonance — but the filter has a “forced” resonance
Each LC tank has its own natural resonance frequency:
At this frequency, a parallel LC tank has maximum impedance. If the tank were sitting alone on a bench, it would peak at 14.029 MHz.
But in a real filter, the tanks are not alone. They are:
coupled to each other,
loaded by the source and load impedances,
and constrained by the Butterworth response requirements.
Once you connect everything together, the system develops multiple resonant modes, and the collective behavior shifts the passband center upward.
This is why the filter’s true center ends up at 14.2 MHz, not 14.029 MHz.
2. Coupling “pulls” the resonant modes apart
A 3‑pole filter has three resonant modes. If the tanks were uncoupled, all three would sit at 14.029 MHz.
But coupling splits them into three slightly different frequencies:
one a bit below the tank resonance,
one near it,
one above it.
The Butterworth design equations choose the coupling so that the middle mode becomes the passband center, and that mode ends up at your design frequency (≈14.2 MHz).
So the tanks are intentionally tuned a little low so that, once everything interacts, the system resonance lands exactly where you want it.
3. Think of it like tuning three musical instruments
Imagine three violins, each tuned to 14.029 MHz. When they play together and acoustically couple, the ensemble’s strongest note shifts slightly upward.
The individual strings haven’t changed tuning — but the system resonance has.
Your filter works the same way.
4. What this means for your frequency‑response plot
If you graph insertion loss (dB) vs. frequency:
At 14.029 MHz Each tank is at maximum impedance, but the filter is not at maximum transmission. You’re on the lower slope of the passband.
At 14.2 MHz The three resonant modes combine to produce the minimum insertion loss. This is the true center of the Butterworth passband.
Above and below The response rises smoothly, with the classic maximally‑flat Butterworth shape.
So the filter’s “flat top” is centered at 14.2 MHz even though the tanks themselves peak at 14.029 MHz.
5. The relationship in one sentence
14.029 MHz is the natural resonance of each individual tank.14.2 MHz is the resonance of the entire coupled system.
The difference is not an error — it’s exactly how a properly designed 3‑pole Butterworth band‑pass filter is supposed to behave.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
My technician class license renewal was pretty easy and I struggled a bit before my general. The vision of a DIY Ham radio came through my brain, quite obnoxiously, interrupting my study for my extra about 2 weeks after I paid ARRL too much for a study guide. Now just after the ADHD kicked in, the real question was, “How am I going to make my own HF radio?” or “How-to?”.
I’m here to tell you the answer to the how-to question is easy. AI is not your enemy. In fact, I wish that I had AI when I was in college. I would be addressed as Dr. Whitehurst today. But beware because with everything AI gives you, it comes with no shame, no caveat, no hesitation, etc. You can’t accept all AI responses as truth or gospel. You can however, use it to accelerate the creation of a DIY HAM radio.
I’m going to use the post image to describe how I used AI to arrive at my design and how I chosen components to accomplish a task within the larger component of RF routing into selected band-pass filters. I first want to make this analogous to fishing. And, if I didn’t catch the big fish it was because “you’re not holding your mouth right” according to my dad. With AI, you’re not going to get the best answer when “you didn’t give it the right prompt”. Let’s begin a session with AI and I’ll you’ll begin to see how this fishing trip goes.
I’ll provide a background to describe the need for the circuit above and we’ll begin just after the requirements. The Freedom7 HF Transceiver decidedly selected 7 bands, 10m, 15m, 17m, 20m, 40m, 80m, 160m for use. I now knew that I would have 7 bandpass filters. I could see my seven filters just after the antenna came into the radio enclosure. Wait a minute, we need a splitter of sorts and really a switching mechanism because our RF doesn’t need to be wasted on all filters. We have this weak RF signal and we need to route it through a band-pass filter and selectively narrowing the spectrum to the band chosen by the radio operator.
We now need to think of components, interfaces, and testing. I could see this thing or black box with one RF input and seven outputs. These interfaces would be SMA. Easy right? So what exactly does this black box need beyond the single input and then outputs into each band-pass filter? How do we select or switch into the output SMA? I could think of two choices: 1) mechanical switch or 2) digital selection. I liked the digital selection because that’s what I learned most about in school. Enter AI.
I’ll skip over the part here where the radio operator will push a momentary switch for the selection of one of the seven bands. Assume that we are using microcontrollers inside and when the operator pushes the button for 20 meters that the microcontroller can send the information needed to drive a chip to route the RF signal to a unique RF output. Let’s now ask AI (Microsoft CoPilot) if there are available chips to route RF signals. We’ll ask the question and I’ll share the AI response here. Ask AI very clearly what you want. And, if backstory is needed give it.
Here goes … Prompt: I’m making a homebrew HF transceiver. The RF ranges between 1.8 and 30 Mhz. Are there IC chips that can route input RF to many outputs based on digital selection?
CoPilot Response: Yes, there are RF switch ICs that can route signals in the 1.8–30 MHz range to multiple outputs using digital control. These are typically SPxT (Single-Pole x-Throw) switches designed for wideband applications.
🔌 Recommended RF Switch ICs for HF Transceivers
Here are some ICs suitable for routing RF signals in your HF range:
IC
Type
Frequency Range
Control
Notes
ADG904BRUZ
SP4T
DC to 2.5 GHz
CMOS
Absorptive switch with low insertion loss analog.com
Digital control: Most switches use CMOS logic (e.g., 3.3V or 5V) for selection.
Routing options: Choose SP4T or SP6T depending on how many outputs you need.
Insertion loss: Look for <1 dB to preserve signal strength.
Isolation: Higher isolation (>30 dB) prevents crosstalk between outputs.
Absorptive vs Reflective: Absorptive switches terminate unused ports to prevent reflections—ideal for RF.
🛠️ Application Ideas
Band switching: Route different frequency bands to separate filters or amplifiers.
Antenna selection: Switch between multiple antennas based on mode or band.
Signal routing: Direct RX/TX paths to different modules or test points.
Would you like help selecting a switch for a specific number of outputs or integrating one into your schematic?
End CoPilot
I did not edit the CoPilot response but you notice that the ADG904BRUZ chip was first in the list. I knew nothing about this chip until I asked AI. I held my mouth right that time, and caught the big fish. I knew that my next step was to find my Golden Field Guide to Fish and look him up. Or, better yet search for a datasheet on the ADG904BRUZ chip.
My microcontrollers are being used for various tasks but they both (yes 2) are powered by 5V. This chip requires a step-down regulator.
I’ll not belabor this post with all of my design details here but I do want to emphasize how important AI can be in figuring all this out. I’ll leave you with some homework. Ask Copilot how two ADG904BRUZ chips could be used with a microcontroller to drive the choice of 7 unique RF outputs. You will be amazed. Just ask it your question.
I’ll end my post today with the following. AI is not always right. I have caught outright untrue responses/results. I have also called AI on these facts and AI provided a second look and agreed with cause for debate. I’ll write more about this in the future. AI is here so use it for what it is. Learn, learn, … and learn some more.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
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