The architecture
Run the transceiver directly from the 12V battery through short fused cable; do not insert an inverter. The solar controller charges the battery while a fused distribution block feeds radio, tuner, USB charging and optional lighting. Physical separation and ferrites keep controller switching noise out of the receiver.
Load and sizing math
Transmit current can exceed 20A, but duty cycle is low in voice operation. Receive draw plus accessories often dominate total hours.
| Load | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| 100W HF radio receive | 20 | 5 | 100 | ~1.5A at 13.8V |
| 100W HF transmit average | 250 | 0.6 | 150 | Voice duty cycle equivalent |
| Tuner / USB / lights | 15 | 5 | 75 | Bench accessories |
| Illustrative total | 325 Wh/day | Before system margin | ||
The illustrative day is roughly 325Wh before margin. A 100Ah LFP battery stores about 1.28kWh nominal, leaving generous reserve and supporting high transmit current. Two 100W panels can replace several hundred Wh on a decent day.
Full parts list
This is a shopping architecture, not a demand that you buy one exact brand. Match voltage, current and connectors before ordering. Budget ranges reflect the class of hardware rather than a live quote.
200W solar array
Target spec: 2×100W rigid/folding panels
Enough harvest for real radio use rather than phone-charger scale.
Budget: $100–$260 each
100Ah LiFePO4 battery
Target spec: 12.8V, 100A BMS
Low voltage sag during transmit and useful all-day reserve.
Budget: $150–$300 each
20A–30A MPPT controller
Target spec: Low-RFI reputation, LFP profile
A cheap noisy controller can destroy HF receive conditions.
Budget: $70–$180 each
Anderson fused distribution panel
Target spec: 30A+ main branch, multiple outputs
Makes radio gear modular and field-serviceable.
Budget: $35–$100 each
Ferrite chokes / snap-ons
Target spec: Mix 31 or suitable HF suppression
Tames switching noise on PV and DC leads.
Budget: $20–$60 each
100W HF transceiver or existing rig
Target spec: 13.8V nominal input
The build assumes a typical 100W amateur HF station.
Budget: $500–$1300 each
Wiring map
Keep the radio feed short, heavy and direct. Put noise suppression near the controller and where cables enter the radio area.
[2x100W PV]-->[PV FUSE]-->[MPPT]-->[100Ah LFP]
|
ferrite on leads
|
[40A MAIN FUSE / BUS]
| | |
Radio Tuner USB/LED
30A 5A 5A
Step-by-step build
Lay out the RF-clean power box
Place controller and PV wiring physically away from the radio, coax and antenna feedline.
Mount the battery and main fuse
Fuse the positive lead close to the battery. Use cable sized for 25–30A continuous radio current with minimal voltage drop.
Install the MPPT
Use twisted DC pairs where practical and leave room for ferrites on controller input/output leads.
Build the Anderson distribution
Create clearly labeled branches for radio, tuner, lighting and USB charging.
Mount and connect panels
Deploy panels away from antenna elements and route PV wire at right angles to coax where crossings are unavoidable.
Power the radio from battery only first
Listen across HF bands and establish a noise-floor baseline before enabling solar charging.
Enable the controller and hunt RFI
Switch PV charging on and listen for birdies/hash. Add ferrites or relocate wiring until noise is acceptable.
Run a transmit test
Transmit into a dummy load or normal antenna and verify battery voltage stays healthy at full RF output.
Commission it before you trust it
The project is not finished when the LED comes on. Run it through a controlled test so the first real failure is not in the field.
- Main battery fuse installed
- Radio branch fuse sized
- No inverter in radio path
- Battery voltage under transmit checked
- MPPT charge profile correct
- HF noise floor compared charge on/off
- Ferrites installed as needed
- Connectors strain-relieved
- Panel/cable clear of antenna
Mistakes to avoid
Undersizing the battery because the panel is large
Panels make energy only when conditions cooperate. The battery has to carry the load through night, cloud and short high-demand events. Size energy storage from watt-hours, not panel watts.
Ignoring standby loads
Controllers, routers, cameras, inverters and cellular hardware can consume power 24/7. On small projects, a 5W always-on device is 120Wh per day—sometimes more than the 'main' load.
Using one fuse for the entire project
Fuse each branch according to its conductor and load. The fuse protects wire, not the gadget. A downstream short should not require an oversized main fuse to clear.
Mounting the panel where the project is instead of where the sun is
The load can sit in shade. The panel cannot. Use a cable run, pole or remote mount to put the collector in the best solar window.
Skipping a low-voltage disconnect
Deep-discharge protection is cheap insurance. Many charge controllers or smart battery systems can disconnect noncritical loads before the battery is abused.
Upgrade path
Add a second battery
For digital modes or long contest sessions, another 100Ah doubles energy and reduces voltage sag.
Add a DC wattmeter
Logging amp-hours in/out makes operating-time planning far more accurate.
Put it on a cart
A rolling field station with mast, battery and folding panels becomes a grab-and-deploy emergency node.
Frequently asked questions
Will a solar controller interfere with HF?
Some do. Use a known low-noise controller, physical separation and ferrite suppression.
Can I run the radio from a power station?
Yes, but direct 12V LiFePO4 avoids inverter loss and may produce a quieter RF environment.
Is 100Ah excessive?
For QRP, yes; for 100W field operation with long receive time, it creates useful reserve.
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