I depends on the design of the radar. The heart of any controlled radio transmitter, including radar, is an oscillator or timebase of some sort which either directly or indirectly determines the operating frequency. Other devices may be present which tune and filter the emissions to a desired spectral profile but they are normally designed around a target frequency determined by the timebase.
You can check the last 3 paragraphs of an article I posted on this website a while back, for a method I developed to change the nominal radar frequency for the purpose of avoiding interference between multiple radars operating in close proximity: http://www.eeweb.com/blog/todd_hayden/micropower-impulse-radar-overview
This was on a wideband transmission device, where the pulsed nature of the transmitter causes a spreading of the energy over a relatively large bandwidth. Because the regulated bandwidth where the device operates is wide enough, it allows small changes in operating frequency. This was achieved by directly shifting the oscillation frequency of the timebase of the entire unit, including the microcontroller which drove the transmitter and synchronous sampling receiver.
There was another way to change our radar operating frequency, covered by a seperate US patent, which also varied the transmitter frequency by dynamically changing the bias voltage to an RF transistor which oscillated at a harmonic of the radar timebase. The RF transistor oscillated nominally on the order of the 2,560th harmonic of the timebase. In the lab we mapped the sensitivity of the oscillation frequency versus bias voltage, allowing us to then shift the frequency between the 2,555th harmonic and the 2,565th harmonic, for example. In this case we only varied the tranmitter frequency but since the change was always a harmonic of the timebase, the synchronous sampling receiver would continue to function.
If the RADAR is a CCW one (largely used for car velocity trafic control), its frequency is continuously varied by a triangular wave witch modulating a oscilator and using the Doppler-Fizeau efect may derive the target velocity.
If the RADAR is a Monopulse one (normaly of military use) , its frequency may be varied if it is of the so called "agile" type, but this is donne through using a computer (witch masters all the RADAR set actions) called "logics" in the some RADAR block diagram or else "synchronizer" in older blocks diagrams.
We denote wavelength by Frequency is how many complete waves go by per second. We denote frequency by Frequency is measured in Hertz = Hz = 1/seconds.
If a wave with a wavelength of 2 meters is going by at a speed of 6 meters/second, then 3 complete waves go by in 1 second. That is, the frequency is 6/2 = 3 waves/second, or 3 Hz. (See units ).Thus
For example, radio station KUGN broadcasts at a frequency of 590 KHz. What is the wavelength of the radio waves?
wavelength = c/frequency = (3 x 108 m/s)/(590 x 103 Hz) = (3 x 108)/(0.590 x 106) m ~ 5 x 102 m = 500 m. this relation will explain ur question the best
Thank u so much for your kind comment bro. But actually i need to know About radar used in ships. Actually my query was, how can i change my radar frequencies or how i can very the frequencies into many within a certain range.? what will be needed in addition with aradar to do that ?
im highly greteful for your kind answer brother. it will help me a lot. i would appreciative if you could help me by giving some more idea about if any additional devices can be placed to devide or change the emitted frequency by a RADAR?
Normally the RADARs used in civilian ships (not military one) uses as a transmiting device a vacum tube called MAGNETRON. Some of that MAGNETRNs are of the type "agile", witch means they can have its transmiting frequency varied in a certain amount. The process may be mechanical or electronic, but In both modes the process is automatic. So it's not manual, as it seems to me be your ideia. Am I right? In my concern there is only one way to change it's frequency through programing the RADAR operation, if possible.
Maybe you can explain further on what sort of frequency emmsion change you are looking for. A transmitter that is broadbband, frequency agile, swept, etc. From the variety of answers you recieved, it is apparent your request was not specific enough.
actually im trying to add any sorts of device that can change the frequencies transmitte by any ships radar. normally the radar available in my country ships can emit in 2 frequencies only. i ant to amke there frequency emmission multiple so that they become invinsible in front of any jamming devies. can you help me in this matter in particular sir. u may sent me emails on my address- nur_2174@yahoo,com i'll be looking forward for your kind reply.
Mr. Geraldo, thank u you so much for your help. can you just give me some idea about " Furuno" radar ? is there any way to bring any change in there? im just a novice guy in this matter
✨ Changing the frequency emissions of radar systems depends primarily on the radar's design, particularly its oscillator or timebase, which sets the nominal operating frequency. Frequency variation methods include tuning the oscillator, using frequency agility techniques, and modulation. Frequency agile radars, such as some magnetron-based transmitters used in civilian ship radars, can vary their frequency automatically within a certain range, either mechanically or electronically, typically controlled by onboard logic or synchronizer circuits. Continuous wave (CW) radars modulate frequency with waveforms like triangular waves for Doppler velocity measurement. To achieve multiple frequency emissions and avoid jamming, wideband or frequency-agile transmitters are employed, often requiring programming or integrated control systems rather than manual adjustment. Additional devices to divide or shift frequencies are not commonly used; instead, frequency changes are implemented within the radar's internal architecture. For specific radar brands like Furuno, technical specifications and capabilities for frequency variation can be found on the manufacturer's website. Overall, frequency emission changes in radar involve oscillator control, modulation schemes, and digital logic for agile operation, with practical application depending on radar type and intended use.
TL;DR: To change a radar’s emission, tune its oscillator/timebase or bias the RF stage; one lab method shifted a transmitter from the 2,555th to 2,565th harmonic. “The heart of any controlled radio transmitter … is an oscillator.” [Elektroda, Todd Hayden, post #21661638]
Why it matters: This FAQ helps marine and RF engineers understand safe, practical ways to retune, sweep, or make emissions agile without breaking receiver sync.
Change the oscillator or timebase that sets the transmitter frequency. Filters and tuning networks follow that core frequency. In practice, designers shift the radar’s master clock slightly to move the emission within its allowed band. “The heart … is an oscillator.” [Elektroda, Todd Hayden, post #21661638]
What does “frequency agility” mean on marine or military radars?
Frequency agility means the radar varies its transmit frequency over a defined range under system control. In shipborne sets using magnetrons, any agility is built-in and automatic rather than user‑controlled. In monopulse military sets, agility is coordinated by the system logic or synchronizer. [Elektroda, Geraldo Lopes Serodio, post #21661639]
Can I manually add a device to vary a ship radar’s frequency?
Not in a supported way on typical civilian magnetron radars. Their frequency—and any agility—is managed automatically. User add‑ons to force manual variation are not part of normal operation. If change is possible, it’s through the radar’s own programmed controls. [Elektroda, Geraldo Lopes Serodio, post #21661644]
How can wideband pulsed radars shift frequency without breaking the receiver?
Shift the master timebase so both transmitter and synchronous sampling receiver stay harmonically related. Designers have changed the microcontroller/timebase frequency slightly to retune emissions while preserving receiver timing. “The synchronous sampling receiver would continue to function.” [Elektroda, Todd Hayden, post #21661638]
Is there a way to retune by adjusting RF transistor bias?
Yes. One approach mapped oscillation frequency versus bias on an RF transistor oscillating near the 2,560th harmonic, then shifted between the 2,555th and 2,565th harmonics to move the transmit frequency. This kept receiver timing aligned to the timebase. [Elektroda, Todd Hayden, post #21661638]
What’s the relationship between radar frequency and wavelength?
Wavelength equals speed of light divided by frequency. Example: a 590 kHz signal has roughly a 500 m wavelength. Use λ = c/f to estimate antenna and propagation behavior when considering frequency changes or band selection. [Elektroda, Ashesh Sharma, post #21661640]
What is a magnetron, and why do ships use it?
A magnetron is a vacuum-tube RF oscillator used as the transmitter in many civilian marine radars. It delivers high peak power with a relatively simple architecture. Some models are “agile,” but their frequency variation occurs automatically inside the radar system. [Elektroda, Geraldo Lopes Serodio, post #21661644]
Does triangular frequency sweeping help measure speed?
Yes for certain continuous‑wave traffic radars. They vary frequency with a triangular modulation and use the Doppler‑Fizeau effect to derive target velocity. This is distinct from pulsed marine radars but illustrates controlled frequency variation in practice. [Elektroda, Geraldo Lopes Serodio, post #21661639]
How do monopulse radars implement frequency changes?
Monopulse radars implement frequency agility under control of their computer “logics” or older‑style synchronizers. The controller coordinates timing, pulse parameters, and frequency plans to support ECCM and tracking performance. [Elektroda, Geraldo Lopes Serodio, post #21661639]
How can I reduce interference between nearby radars?
Retune the nominal operating frequency slightly by altering the radar’s timebase so units in proximity use offset channels. This method was used on a wideband pulsed radar to avoid mutual interference while keeping receiver synchronization intact. [Elektroda, Todd Hayden, post #21661638]
What should I check before attempting changes on a Furuno marine radar?
Review the official Furuno product specifications and documentation first. Vendor materials outline supported modes, bands, and any configurable features. Unauthorized modifications are outside normal operation and may violate approvals. [Elektroda, Geraldo Lopes Serodio, post #21661650]
What does “wideband” mean here?
In pulsed systems, the short transmit pulse spreads energy over a relatively large bandwidth. If regulations and design allow, small timebase shifts move the emission within that wide band without redesigning RF filters. [Elektroda, Todd Hayden, post #21661638]
Can I expand a two‑frequency marine radar into many frequencies to defeat jamming?
Not by external add‑ons on civilian magnetron sets. Their frequency plan and any agility are internal and automatic. Modifying beyond supported controls risks noncompliance and loss of performance. Use built‑in programming if available. [Elektroda, Geraldo Lopes Serodio, post #21661644]
Quick 3‑step: How to apply a small frequency offset on an impulse radar
Slightly shift the radar’s master timebase frequency within allowed limits.
Verify the synchronous receiver remains harmonically aligned with the timebase.
