I just pre-ordered the new Icom IC-7300MK2. Its reduced current draw finally makes this legendary HF rig off-grid friendly!
If you’ve followed my YouTube channel and my book Off-Grid Power for Emergency Communications, you already know the most important spec for a grid-down radio isn’t “100 W output.” It’s how much current the radio consumes while you’re listening. Most emergency operating is receive-heavy. That’s why I’m paying close attention to Icom’s new IC-7300MK2.
In Off-Grid Power for Emergency Communications I stressed the importance of both receive efficiency and transmit efficiency. For portable operators, lower current draw means smaller, lighter batteries. For off-grid home stations, it means longer runtimes on the same energy storage. Like it or not, energy efficiency matters. If your radio is idling at one or two amps while doing nothing, it will quickly drain your reserves. Efficiency cannot be an afterthought—it must be part of the plan.
What changed in the MK2
Icom states the MK2 reduces RX standby current by about 23% versus the original 7300. Their MK2 spec sheet now shows 0.7 A (typ.) vs 0.9 A on the older model.
Why receive current dominates your power plan
In real grid-down emergency scenarios you’re on watch most of the time, waiting for incoming voice or data connections, then transmitting in short bursts. A lower RX current shrinks your daily Wh budget, allowing greater energy autonomy from the same battery storage that previously fell short due to the higher current draw of the original IC-7300.
The math that matters (13.8 V reference)
Old IC-7300 RX: 0.9 A → 12.42 W → 298 Wh/day IC-7300MK2 RX: 0.7 A → 9.66 W → 232 Wh/day Savings: ~66 Wh per 24-hour day
Battery + solar are a pair at 65°N (spring/autumn)
Use realistic peak-sun-hour (PSH) ranges for Rovaniemi-latitude operations.
April: daily shortwave energy climbs from about 2.5 to 3.9 kWh per square meter (≈0.8 to 1.2 kWh per square foot), equal to roughly 2.5–3.9 PSH.
September: daily shortwave energy falls from about 2.9 to 1.2 kWh/m² (≈0.9 to 0.4 kWh/ft²), or 2.9 down to 1.2 PSH.
That’s why spring feels easy and autumn gets tight fast.
Panel watts needed to recharge a 24-hour receive watch (assume 85% overall efficiency: MPPT + wiring + charge/discharge)
April “mid” day (≈3.2 PSH, about 3.2 hours at full sun)
Old 7300: 298 Wh / (0.85 × 3.2) ≈ 110 W (≈0.11 kW)
MK2: 232 Wh / (0.85 × 3.2) ≈ 85 W (≈0.085 kW)
Early April (≈2.5 PSH, about 2.5 hours at full sun)
Old: ≈ 140 W (≈0.14 kW)
MK2: ≈ 109 W (≈0.11 kW)
September average early-month (≈2.0 PSH, about 2 hours at full sun, conservative)
Old: ≈ 175 W (≈0.18 kW)
MK2: ≈ 136 W (≈0.14 kW)
Late September, overcast-prone days (≈1.2 PSH, barely over 1 hour at full sun)
Old: ≈ 292 W (≈0.29 kW)
MK2: ≈ 227 W (≈0.23 kW)
These peak-sun-hour estimates are backed by hourly and daily solar radiation data for the Rovaniemi area, and they match the monthly solar irradiation profiles published by the European Union’s PVGIS (Photovoltaic Geographical Information System) for northern Finland.
Battery autonomy targets for northern latitudes
Plan battery for dark hours plus “no-sun” buffers; then size solar to refill the battery during your expected PSH window.
Receive-only autonomy (12.8 V LiFePO₄, continuous listen)
Old 7300: 298 Wh/day ≈ 23.3 Ah/day MK2: 232 Wh/day ≈ 18.1 Ah/day
Examples
One long polar shoulder-season night + bad morning (18 hours no sun) Old: ~17.5 Ah MK2: ~13.6 Ah 36 hours no sun (storm day) Old: ~35 Ah MK2: ~27.2 Ah 72 hours no sun (front + overcast + recovery) Old: ~70 Ah MK2: ~54 Ah
Framed another way: with a 50 Ah LiFePO₄ battery, the old IC-7300 runs for a little over two days of continuous receive. The MK2 stretches the same pack to nearly three full days. That extra day of runtime is the difference between hoping for sun tomorrow and knowing you’ll last until it comes.
What this means in a real kit
Same battery, more uptime: a 50 Ah LiFePO₄ yields ~51.5 hours on the old 7300 vs ~66.3 hours on the MK2 (RX-only).
Same uptime, less weight: a 3-day RX-only watch drops from ~70 Ah to ~54 Ah with the MK2. That’s one fewer brick in the ruck and more margin for cold-weather losses.
Weight savings matter: Power Queen’s 12 V 50 Ah LiFePO₄ weighs around 11–15 lb (5–6.8 kg), while their 100 Ah version comes in at 25–30 lb (11.3–13.6 kg). Dropping from 100 Ah to 50 Ah saves 15–19 lb (7–9 kg)—roughly half the weight—without losing autonomy, thanks to the MK2’s lower current draw.
Don’t waste storage: we don’t want to burn through energy reserves while the radio is just sitting on receive. Lowering RX current means more of your stored energy is held back for when it really matters—transmitting.
Smaller panel in spring, survivable panel in autumn: the MK2 trims about 20–65 W of panel requirement depending on PSH, which is the difference between a single 120 W foldable and needing to stack panels when September turns gray.
Final Thoughts
Efficiency and conservation aren’t optional in off-grid communications—they’re survival tools. After years of relying on QRP radios with external amplifiers to balance power draw and capability at my home station, I’m adopting the IC-7300MK2 for home and mechanised field use. It finally delivers 100 watts of HF output without the heavy current penalty. No other major manufacturer is offering a full-power HF radio with such a low receive current. For operators who live by their batteries and panels, that makes the MK2 more than just an upgrade—it makes it a lifeline.
Bottom Line
At 65°N in spring and autumn, the IC-7300MK2’s lower 0.7 A receive draw shaves roughly 66 Wh from each 24-hour watch. That reduces both the amp-hours you must carry through long dark periods and the watts of panel you need to claw that energy back when the PSH window is short. It’s not a footnote—it’s the difference between maintaining a 24/7 watch and going dark by morning when September turns ugly.
Off-Grid Power for Emergency Communictions
If you found this post useful, topics like energy efficiency, solar sizing, battery autonomy, and real-world field strategies are covered in much greater depth in my book Off-Grid Power for Emergency Communications. It’s written for radio operators, preppers, and anyone serious about keeping the lights on when the grid goes dark. You can find it on Amazon here: https://www.amazon.com/author/julian-oh8stn
Sources
- Icom Japan IC-7300MK2 announcement: “RX standby current consumption reduced by about 23%.”
- PileupDX product page noting 0.7 A RX standby for IC-7300MK2.
- Rovaniemi shortwave energy in April (2.5 → 3.9 kWh/m²).
- Rovaniemi shortwave energy in September (≈2.9 → 1.2 kWh/m²).
- IC-7300 (original) TX current reference ~21 A at 100 W.
- PVGIS monthly irradiation tool for northern Finland validation.
73,
Julian oh8stn
Like what I do, check out my books:
https://www.amazon.com/author/julian-oh8stn
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