FAQ
TL;DR: For an AM receiver IF board running up to 10.7 MHz, keep leads short and “separate power and ground planes onto adjacent layers.” [Elektroda, Anonymous, post #21684148]
Why it matters: This helps beginners ask the right layout questions, avoid oscillations, and choose a sensible 2‑ vs 4‑layer stack for didactic builds.
Quick-Facts
- Typical AM IF: 455 kHz; 1960s sets used single‑sided PCBs without ground planes. [Elektroda, Anonymous, post #21684145]
- Your project uses two IFs: 10.7 MHz and 455 kHz (front end + IF boards). [Elektroda, Anonymous, post #21684146]
- Two‑layer option: ground on component side, all traces on solder side. [Elektroda, Anonymous, post #21684145]
- Four‑layer option: adjacent power/ground planes maximize interplane capacitance. [Elektroda, Anonymous, post #21684148]
- Place bypass caps with tiny lead/track lengths to cut series inductance. [Elektroda, Anonymous, post #21684148]
Quick Facts
- Typical AM IF: 455 kHz; 1960s sets used single‑sided PCBs without ground planes. [Elektroda, Anonymous, post #21684145]
- Your project uses two IFs: 10.7 MHz and 455 kHz (front end + IF boards). [Elektroda, Anonymous, post #21684146]
- Two‑layer option: ground on component side, all traces on solder side. [Elektroda, Anonymous, post #21684145]
- Four‑layer option: adjacent power/ground planes maximize interplane capacitance. [Elektroda, Anonymous, post #21684148]
- Place bypass caps with tiny lead/track lengths to cut series inductance. [Elektroda, Anonymous, post #21684148]
Which IFs are acceptable for this AM receiver project?
The thread confirms two IFs: 10.7 MHz and 455 kHz. Use 455 kHz for a classic AM chain, or 10.7 MHz if your front end and filters are designed for it. Keep consistency across mixers and filters. Label each stage clearly for didactic learning. [Elektroda, Anonymous, post #21684146]
Is a single‑sided board OK at 455 kHz?
Yes. Historical AM sets at 455 kHz often used single‑sided PCBs without ground planes. That frequency is forgiving if leads are short and parts are placed tightly. For teaching, you can still add a ground pour to show best practices. [Elektroda, Anonymous, post #21684145]
Should I choose 2‑layer or 4‑layer for the IF board?
A 4‑layer stack with adjacent power/ground planes gives built‑in decoupling. However, with ≤10.7 MHz sine signals, a 2‑layer board works if you use a solid ground side and local bypassing. “Your design uses no frequencies above 10.7 MHz.” [Elektroda, Anonymous, post #21684148]
How should I route ground and signal on a 2‑layer board?
Use the component side as an uninterrupted ground plane and keep all signal routing on the solder side. Stitch grounds where needed. This layout simplifies return paths and reduces coupling between IF stages. [Elektroda, Anonymous, post #21684145]
Do I need a dedicated power plane at these frequencies?
Not necessarily. A supply trace works if every supply pin has a local bypass cap to ground with minimal lead and track inductance. Keep runs short, and star‑route feeds to sensitive stages. [Elektroda, Anonymous, post #21684148]
What about trace width and length for 10.7 MHz and 455 kHz?
Prioritize short lengths over width. Keep component leads and traces to bypass caps very short to minimize series inductance. At ≤10.7 MHz, controlled‑impedance widths are unnecessary for typical receiver currents. [Elektroda, Anonymous, post #21684148]
How do I place bypass capacitors correctly? (3‑step)
- Put each cap adjacent to its device supply pin.
- Connect the cap ground directly to the ground plane with a short via.
- Feed the device from the supply trace after the cap node.
[Elektroda, Anonymous, post #21684148]
Can I prototype the IF board without making a PCB?
Yes. Use “ugly construction” on a single‑sided copper‑clad board, treating the unetched copper as a ground plane. It is effective for RF prototyping and quick didactic experiments. [Elektroda, Anonymous, post #21684148]
Any real‑world speed example for ugly construction?
One contributor prototyped an MC10EL52 ECL flip‑flop clocked at 540 MHz using this method. That illustrates strong headroom versus a 10.7 MHz IF board. [Elektroda, Anonymous, post #21684151]
How should I arrange stages for didactic clarity?
Group and label each circuit block: front end, mixer, IF amps, detectors. Keep signal flow left‑to‑right and maintain physical separation between high‑gain IF stages. The poster shared this teaching‑oriented alignment. [Elektroda, Anonymous, post #21684152]
Is 10.7 MHz a normal choice for AM?
Another poster questioned which AM receiver uses a 10.7 MHz IF. If you pick 10.7 MHz, ensure your mixers, IF filters, and detectors suit that plan. Document the rationale for learners. [Elektroda, Anonymous, post #21684149]
What is IF (intermediate frequency) in this context?
IF is the fixed frequency after mixing the incoming RF with a local oscillator. In this project, that’s 455 kHz or 10.7 MHz as declared by the builder. [Elektroda, Anonymous, post #21684146]
How do I minimize unplanned oscillations in IF amplifiers?
Shorten leads and traces, especially around bypass capacitors, to reduce series inductance. Use a continuous ground plane and isolate high‑gain stages. Edge‑case: excessive lead length can cause oscillation or detuning. [Elektroda, Anonymous, post #21684148]
Can I mix power and ground on one plane?
Keep them separate. The recommended approach is adjacent power and ground planes to maximize plane‑to‑plane capacitance for decoupling. Quote: “separate power and ground planes onto adjacent layers.” [Elektroda, Anonymous, post #21684148]
What stackup and routing pattern helps beginners learn fastest?
For 2‑layer teaching boards, make the top a near‑solid ground and route signals on the bottom. Keep each functional block compact and clearly marked. This mirrors the thread’s suggested practice. [Elektroda, Anonymous, post #21684145]
