Part of our The Icom IC-7300 Mark II: The Complete Guide.
RMDR gets thrown around in spec sheets and reviews without much explanation of what it actually means for how a radio sounds in real conditions. Here’s the plain version.
What RMDR actually measures
Reciprocal mixing dynamic range measures how well a receiver can pull a weak signal out of the noise when there’s a strong signal nearby on a close frequency spacing. A radio with poor RMDR lets that strong nearby signal smear noise across the band, burying weaker signals near it even though they’re technically on a clear frequency.
What actually changed on the Mark II
Icom improved RMDR to roughly 105-113 dB at 2 kHz spacing on the Mark II, more than a 12 dB improvement over the original IC-7300. Phase noise on transmit also improved by about 12 dB at 1 kHz offset, meaning your own transmitted signal is cleaner and less likely to splash noise onto adjacent frequencies.
Where you’ll actually notice it
This matters most in crowded band conditions, a busy contest weekend, a dense DX pileup, or any situation with strong signals packed close together. A weak station two kilohertz away from a booming one is exactly the scenario RMDR describes, and it’s precisely where the Mark II’s improvement shows up as fewer phantom noises and better ability to actually copy the weak station.
Where it won’t matter much
On a quiet band with well-spaced signals, or for casual ragchewing away from crowded conditions, you’re unlikely to notice a meaningful difference from RMDR improvements alone. It’s a real upgrade, but it’s most valuable in specific, demanding conditions rather than as a blanket improvement to every contact.
The short version
- RMDR describes how well a receiver handles a weak signal near a strong one.
- The Mark II improved this by more than 12 dB over the original IC-7300.
- It matters most in crowded conditions like contests and dense pileups.
- It’s a real, measurable improvement, but its practical impact depends heavily on how crowded the bands you operate on actually are.
It’s worth understanding what the number actually means rather than just treating it as a bigger-is-better spec, since its real-world value is very situation dependent.