Solid-State vs Magnetron Marine Radar: Koden KRS vs MDC
A journey through the mist, a question about watts, and the engineering decisions behind the picture on the bridge.
The harbour was there a moment ago
First the distant coastline softens. Then the harbour buildings disappear. Before long, the view through the bridge windows is mostly grey, with a few drops creeping down the glass and a wiper working harder than anyone would like.
Inside, the radar scanner is already turning. An echo appears near the channel. Another develops farther out. The watchkeeper checks the picture against the chart and the other information available, while the kettle quietly completes the least demanding job on the bridge.
This imagined approach gives us a practical way to explain solid-state vs magnetron marine radar. Both technologies can provide information when visibility is poor. The differences lie in how they transmit, process echoes and fit into the vessel’s operating and maintenance arrangements.
We will use two specific examples: the Koden KRS solid-state range and the Koden MDC-7000P/7900P magnetron range. Along the way, we will look at the questions an engineer asks and the decisions a purchaser needs to make.
The key point: KRS uses a 110 W peak-output solid-state transmitter with CHIRP pulse compression. The MDC scanners considered here use 12 kW or 25 kW peak-output magnetron transmitters. Those figures alone cannot tell you which system will detect a particular target better.
How does the radar know something is there?
The return on the screen has no convenient sign saying “vessel” or “buoy”. It is an echo that needs interpretation. Before considering what it means, it helps to understand how it arrived.
The scanner transmits microwave energy through its antenna. When that energy encounters an object, some may be reflected back towards the radar. The receiver detects the returning signal, and the system processes it into a radar picture.
The time between transmission and return provides the target’s range. The antenna’s direction provides its bearing relative to the radar’s reference. Both KRS and MDC use this fundamental principle.
“Only 110 watts? The other one says 25 kilowatts.”
It is the sort of question that comes up while comparing quotations at a desk—and returns to mind when looking at a working radar. On paper, 110 W beside 25,000 W looks like a rather uneven contest.
However, peak transmitter power is not a complete measure of radar performance. The pulse duration, waveform, receiver and signal processing matter too.
What the KRS solid-state transmitter does
The KRS uses semiconductor transmitter technology instead of a magnetron. Its specified peak output is 110 W, and it uses CHIRP pulse compression.
A CHIRP pulse changes frequency during transmission. With a longer coded pulse, the radar can transmit energy over more time. Receiver processing recognises that frequency pattern and compresses the echo in time, helping retain range detail that an ordinary long, uncompressed pulse would blur.
This compression happens in the signal processing. The radar does not send out a long pulse and somehow make the physical echo shrink while it travels back through the air.
What the MDC magnetron transmitter does
The MDC RB808P scanner uses a 12 kW peak-output magnetron; the RB809P uses a 25 kW peak-output magnetron. A magnetron is a vacuum electronic device that generates microwave energy.
These systems transmit conventional pulses and provide selectable pulse widths. The MDC operating manual explains the trade-off: shorter pulses help separate closely spaced targets in range, while longer pulses provide more energy and sensitivity for longer-range work.
Both approaches involve decisions about energy and detail. Simply dividing 25,000 by 110 tells us the ratio between two peak-power ratings. It does not establish a detection-performance ratio.
The useful purchasing question is: “What will this complete system do for our vessel?”
The screen gets busier—but not everything is a vessel
A shower moves across the approach. The radar picture becomes less tidy. Returns spread across part of the display, and the area near the vessel looks busier as echoes from the sea surface compete with the things the watchkeeper wants to see.
This introduces an important distinction: fog, rain and sea clutter are not the same radar problem. Radar can provide information when fog restricts the visual lookout. Rain can itself create echoes and affect detection, while waves can produce sea clutter.
Both Koden operating manuals cover adjustments for the radar picture. Gain controls sensitivity; sea and rain anti-clutter controls help manage unwanted returns. These controls require judgement: excessive suppression can also remove weak echoes that matter.
The watchkeeper adjusts the picture carefully and continues checking the return ahead. The objective is useful information, not a screen tidy enough for a sales photograph.
Another radar can also introduce interference. We cover that separately in Marine Radar Interference Explained.
Why radar and AIS belong in the same conversation
One return has associated AIS information. Another has no AIS label. That second echo still deserves attention: an empty label is not an empty patch of sea.
Radar detects reflected energy. AIS receives transmitted information from equipped stations. A target may have no AIS equipment, may not be transmitting, or may not be received by your installation.
AIS information can help identify and understand traffic, but it does not replace radar observation. Equally, a radar echo does not automatically provide a vessel’s identity. Our guide to how AIS works on a boat explains the distinction; the Class A versus Class B comparison covers the equipment types.
Choosing a display the bridge can use
Koden’s KRS range provides four display options. All four systems use the same RSB-111P scanner and RSA-1SP 6 ft antenna; choosing a larger display does not increase the transmitter’s peak power.
| KRS system | Display model | Nominal system size |
|---|---|---|
| KRS-1611P | RSD-16P | 16-inch class |
| KRS-1911P | RSD-19P | 19-inch class |
| KRS-1211P | RSD-12P | 22-inch class |
| KRS-1411P | RSD-14P | 24-inch class |
The MDC arrangement considered here uses the MRD-108P display and MRO-108P operation unit. Space for the controls, reach from the operating position and visibility of the display deserve attention during selection.
Target tracking and CPA/TCPA information support assessment, but their quality depends on the tracking and relevant sensor inputs. An automated target label is still information for the watchkeeper to evaluate.
The mast has a say in the radar picture
Before this imagined passage, there was a less atmospheric visit to the vessel: measuring, checking cable routes and discussing where the scanner could go. Nobody brought a fog machine. The engineer did, however, ask awkward questions about the mast.
Structures can obstruct the radar beam and create shadow or blind sectors. Reflections from the vessel’s own structure can also produce misleading echoes. A blank or mute sector setting manages a defined sector; it does not restore visibility through an obstruction.
Scanner position, antenna clearance, mounting strength, power, earthing, cabling and commissioning therefore belong in the quotation—not as surprises after the equipment arrives.
KRS uses the RSA-1SP 6 ft antenna. The MDC documentation lists RW701A-04 4 ft, RW701A-06 6 ft and RW701B-09 9 ft open-array options. The precise scanner-and-antenna configuration must be checked when specifying the system.
For an existing installation with unexplained behaviour, our marine electronics diagnostics article explains the value of checking the connected system as well as the device showing the symptom.
What does each radar need over its working life?
The purchaser’s questions began long before the mist arrived. How quickly is the radar available? What needs servicing? What happens when a component needs replacing and the vessel has a sailing schedule to keep?
Those questions reveal a practical difference between solid-state and magnetron ownership.
Start-up: distinguish power-on from standby
KRS documentation specifies approximately 40 seconds from power-on to transmit and under 5 seconds from standby to transmit. “No magnetron warm-up” should not be interpreted as “the complete system boots instantly”.
The MDC operating manual specifies a preheating countdown of 120 seconds for MDC-7012P/7912P, using the 12 kW scanner, and 180 seconds for MDC-7025P/7925P, using the 25 kW scanner. After preheating, the radar can be placed in transmit mode.
These timings describe readiness. Preparation for a passage should include having the radar available and checked before it is needed.
Maintenance: no magnetron is a real difference
KRS has no magnetron to replace. Koden describes its solid-state design as offering reduced maintenance. That removes a particular transmitter service item; it does not remove the need to inspect the antenna, mounting, cables and the rest of the installation.
The MDC manuals identify the magnetrons as MAF1565N for RB808P and M1568BS for RB809P. They also describe transmitter-hour information as useful when assessing magnetron life expectancy.
Which Koden radar fits the vessel?
The decision starts with the vessel’s requirements. Transmitter technology is one part of that specification, alongside approval, antenna arrangement, bridge layout, interfaces and support.
| Question | Koden KRS | Koden MDC-7000P/7900P |
|---|---|---|
| Transmitter? | Solid-state, with CHIRP pulse compression | Conventional magnetron pulse transmission |
| Peak RF output? | 110 W | 12 kW RB808P or 25 kW RB809P |
| Antenna arrangement? | RSA-1SP 6 ft open array | 4 ft, 6 ft and 9 ft options; specify the required combination |
| Readiness? | Approx. 40 seconds power-on to transmit; under 5 seconds standby to transmit | 120-second preheat for 12 kW models; 180 seconds for 25 kW models |
| Maximum instrumented range? | 96 NM | 64 NM for 12 kW; 96 NM for 25 kW |
| Magnetron replacement? | No magnetron fitted | Model-specific magnetron is a service component |
| Display arrangement? | Four RSD display options across the KRS range | MRD-108P display with MRO-108P operation unit |
Approval comes before preference
Koden describes KRS as an IMO type-approved radar, with the supplied manuals stating current compliance for CAT 2 and CAT 3. The category table covers CAT 3 below 500 GT and CAT 2 from 500 GT to below 10,000 GT. This article does not present KRS as CAT 1 equipment.
Confirm the approval documentation for the exact system and vessel. A transmitter’s wattage or a display’s diagonal measurement is not a substitute for that check. The IMO radar performance standard MSC.192(79) provides the category and performance framework.
KRS deserves consideration where its approval scope and configuration fit the vessel, and rapid availability from standby and the absence of magnetron replacement are valuable.
MDC deserves consideration where its conventional 12 kW or 25 kW arrangement, antenna choices and bridge controls meet the requirement, with magnetron servicing included in the ownership plan.
A meaningful performance comparison would need defined targets, conditions, settings and installations. The specifications alone do not justify declaring either system the winner in every situation.
Back on the bridge, the fog hasn’t read the brochure
Outside, the harbour entrance is still hidden. On the display, the watchkeeper checks the echo’s range and bearing again, observes how it develops over successive sweeps and compares it with the other information available.
Nobody is admiring the wattage now. What matters is a useful picture, an understanding of its limitations and a watchkeeper who knows how to interpret it.
The engineer’s work is part of that picture: the scanner position, sound electrical supply, alignment and sensor integration. The purchaser’s decisions are there too: the specified equipment, service arrangements and time allowed for a proper handover.
Radar remains one part of navigation. The IMO’s explanation of the collision regulations covers the continuing importance of a proper lookout, safe speed and assessment of collision risk. Neither solid-state processing nor a high-power magnetron takes those responsibilities away.
Eventually, the harbour wall begins to take shape through the mist. The scene outside can be compared with the radar picture. Later, with the vessel secured alongside, somebody remembers the tea.
It is cold, naturally. Some marine problems remain beyond even a new radar.
The right radar choice brings the engineering and purchasing decisions together: a suitable system, properly installed and maintained, giving the bridge team useful information when the view outside offers very little.
Questions that come up when comparing quotations
Is 110 W solid-state radar weaker than 12 kW magnetron radar?
Peak power alone cannot establish that. KRS combines its 110 W peak-output transmitter with CHIRP pulse compression. MDC uses high-peak-power conventional pulses. Detection depends on the complete radar, waveform, antenna, target and conditions.
Does solid-state mean maintenance-free?
No. KRS has no magnetron replacement requirement, but its scanner, mounting, cables, power supply and other system components still need appropriate inspection and maintenance.
Will a 96 NM radar see a small boat at 96 NM?
The maximum instrumented range does not guarantee target detection at that distance. Target height and characteristics, antenna height, propagation and operating conditions all affect detection.
Does a larger KRS display mean a more powerful scanner?
No. The four KRS systems covered here use the same RSB-111P scanner and RSA-1SP 6 ft antenna. Display choice changes the bridge presentation, not the specified 110 W transmitter output.
Can AIS replace radar?
AIS and radar provide different information. AIS depends on transmitted data being available and received; radar detects reflected energy. An echo without an AIS label can still represent an important target.
Make the radar specification fit the vessel
Discuss your vessel, existing equipment and operating requirements with F&C Marine. Include the required approval, available scanner position, bridge space and whether this is a new installation or replacement.
Explore our marine electronics diagnostics or browse the Marine Electronics Knowledge Base for related guides.