Ham Radio Power Supplies and Battery Backup
Every ham radio station runs on DC power — typically 13.8 volts, the standard operating voltage that matches a fully charged 12V lead-acid battery. Your power supply is the foundation of your station's reliability. An undersized or noisy power supply causes transmit power reduction, audio problems, and RFI in your receiver. A quality regulated supply with adequate current capacity is one of the most important non-radio investments in your station.
Switching power supplies
Modern switching power supplies use high-frequency transistor switching to regulate voltage, making them compact and efficient. A 30A switching supply can fit in a box the size of a thick paperback book compared to a linear supply of equivalent rating that might weigh 5 kg. The trade-off is that switching supplies can generate RF noise that appears in your receiver, particularly on the lower HF bands. Quality switching supplies from manufacturers like Astron (SS series), MFJ, and Samlex include adequate filtering. Budget switching supplies from unknown manufacturers often have poor RF filtering and cause noise problems.
Linear power supplies
Linear power supplies use a transformer and linear regulator to produce clean DC with virtually no RF noise — they are the gold standard for quiet operation in an HF station. The downside is weight and size — an Astron RS-35M (35A linear) weighs about 7 kg. Linear supplies are the choice for operators who experience noise problems from switching supplies, particularly on 160m and 80m. The Astron RS-20M, RS-35M, and RS-50M are the industry standard. They are expensive but last decades — used Astrons are excellent value.
| Station Type | Peak Current Draw | Recommended Supply |
|---|---|---|
| HT charger and accessories only | 3–5A | 10A switching supply |
| VHF/UHF mobile radio at 50W | 10–12A | 15–20A supply |
| 100W HF transceiver | 18–22A | 25–30A supply |
| 100W HF + accessories + digital | 20–25A | 30A supply minimum |
| Legal limit amplifier (1500W) | 50–60A | Dedicated 240V supply |
Why battery backup matters
Grid power fails during the exact scenarios when amateur radio EmComm is most needed — severe weather, natural disasters, and infrastructure outages. A battery backup that can power your station for several hours turns your home station into a resilient communications asset rather than a weather-dependent one. Even for non-EmComm operators, a battery backup prevents data loss from unexpected power interruptions during digital mode sessions and allows continued operation during brief outages.
Battery chemistry comparison
Sealed Lead Acid (SLA) batteries are inexpensive and proven but heavy and requiring careful charge management to avoid sulfation. AGM (Absorbed Glass Mat) is a better SLA variant — more vibration resistant and less gassing. LiFePO4 (Lithium Iron Phosphate) has transformed portable and backup power for ham radio — it is 50–60% lighter than equivalent SLA capacity, handles more charge/discharge cycles, and maintains better voltage under load. The upfront cost is 2–3x that of SLA, but the service life is significantly longer. For any application where weight matters, LiFePO4 is the clear choice.
| Supply | Type | Rating | Best For |
|---|---|---|---|
| Astron RS-35M | Linear | 35A continuous | Quietest operation — best for sensitive HF receivers |
| Astron SS-30 | Switching | 30A | Compact switching with good RF filtering |
| Samlex SEC-1235M | Switching | 35A | Good value switching supply with meters |
| MFJ-4225MV | Switching | 25A | Compact, includes volt/amp meters |
| Bioenno 30Ah LiFePO4 | Battery | 30Ah | Portable backup — powers 100W radio 1–2 hours |
| Battle Born 100Ah LiFePO4 | Battery | 100Ah | Extended backup — 4–8 hours at 100W operation |
How many amp-hours of battery do I need for EmComm backup?
A 100W HF radio draws about 20A at full transmit power. In practice during a voice net, transmit duty cycle is maybe 25–30% — so average current draw is 5–7A. A 30Ah LiFePO4 battery provides roughly 4–6 hours of sustained net operation. For 12 hours of continuous EmComm capability, a 100Ah battery is the standard target. Add solar charging capability for extended operations beyond one day.
Can I use a car battery as a ham radio power supply?
A car battery can power a ham radio station in an emergency. However, car batteries are designed for high-current starting loads, not sustained discharge — deep discharging a car battery repeatedly damages it. A deep-cycle marine battery is much better suited for sustained ham radio use. LiFePO4 batteries are designed specifically for deep-cycle applications and are the best choice for any battery-powered station.
What is the Anderson Powerpole connector?
Anderson Powerpole connectors are the ARRL/ARES standard for 12V DC connections in amateur radio. They are genderless (both sides are identical), rated for 15–45A depending on the contact size, and mate with themselves in any orientation. ARES groups and EmComm operators standardised on Powerpoles so that power connections between stations and equipment are interchangeable during deployments. If you plan any EmComm involvement, wire your station equipment with 30A Powerpole connectors on all 12V DC power cables.
Should I run my radio directly from a battery or through a power supply?
Running directly from a battery (or through a battery maintained by a charger) is actually a very clean power source — batteries have no switching noise and act as a large capacitor that absorbs RF transients. Many contest and DX operators prefer battery-backed operation for its noise characteristics. The practical approach for a home station is a quality switching or linear supply with a battery in parallel — the supply handles the steady-state load while the battery absorbs transmit peaks and provides backup if power fails.