Replacing our radar: Magnetron or Solid State

[engr_x2]

Replacing our 4' Furuno open array/GaAs .....8-tone display.

Does anybody know if this old unit will interface with the TimeZero program?

Also, we are trying to decide on a Magnetron or Solid State unit. My understanding of radar is the more peak power, the better (improves signal to noise). But the solid state units have more internal capability that is not on the magnetron units. So which one is best? Our application is inland/coastal waterways. ---We want to be able to see lobster/crab pot buoys and floating logs if possible. Plus, sometimes the fog can be really thick. Thanks.

 

[Quitsa]

It's not quite so simple to say more peak power is better when comparing solid state to magnetron. The most powerful solid state radars have much lower peak power than even a small magnetron dome. My DRS25A-NXT 6 foot array solid state radar has only 200W peak power. Compare that to a little DRS4D magnetron dome, which has 2 kW or 100 times the peak power. But the solid state radar has longer pulses and other features that allow it to deliver enough energy on targets to do a much better job than the small magnetron. It picks up small lobster pot floats at long range that would never show on the magnetron dome.

I think the solid state radars probably have some advantages for what you do. From my experience with comparable solid state and magnetron open arrays, the target tracking is faster and often more accurate, which is very helpful in crowded waterways with lots of boats. Although I don't use it myself being old-fashioned, they also have the capability to paint targets red and green to indicate whether there is any risk of collision.

Another benefit is the much lower radiation exposure to crew who happen to pass through the beam and the near "instant on" with no wait for the magnetron to warm up.

In the end your ability to see small targets is a function of the size array and power within each category. A 200W six foot open array like mine will blow away any magnetron except a 25kW six foot array, to which it is quite comparable in performance. Rather than focus on power, fit the largest array that is within your budget if you want to see small targets at ranges less than 2-3 miles. Better to have a 6kW magnetron with a six foot array than a 25kW with a 3.5 foot array to use an example of magnetron radars. The same is true of the solid state equivalents.

 

[engr_x2]

Thanks for your input. There seems to be some "magic" that they can do with the longer pulse than with a magnetron. Their "Complete Guide to Marine Radar" says the magnetron has an 0.3% duty cycle compared to 10% with the equivalent solid-state version. And the claim is that their model numbering scheme tries to set up an equivalence in performance. The exception is that the magnetron has less overall capability on the display end. So, I think I'm going to have to do more research to really understand what's going on here. But nevertheless, thanks for your experience with your 6ft array. We are limited to a 4' because it has to fit within another arch that supports the satellite dish, but I have also thought of swapping positions of the dish and putting the radar on top. But then I give up some of the direct overhead coverage. ---Everything is a trade-off.

 

[engr_x2]

Just found an article on how the innards work and why the NXT is better over a magnetron: https://www.westmarine.com/west-advisor/New-Radar-Technology.html. Starting to become clearer: they are now doing chirping of the emitted radar pulse to get around the limitations of a fixed single frequency.

 

[Quitsa]

It's not quite so simple to say more peak power is better when comparing solid state to magnetron. The most powerful solid state radars have much lower peak power than even a small magnetron dome. My DRS25A-NXT 6 foot array solid state radar has only 200W peak power. Compare that to a little DRS4D magnetron dome, which has 2 kW or 100 times the peak power. But the solid state radar has longer pulses and other features that allow it to deliver enough energy on targets to do a much better job than the small magnetron. It picks up small lobster pot floats at long range that would never show on the magnetron dome.

I think the solid state radars probably have some advantages for what you do. From my experience with comparable solid state and magnetron open arrays, the target tracking is faster and often more accurate, which is very helpful in crowded waterways with lots of boats. Although I don't use it myself being old-fashioned, they also have the capability to paint targets red and green to indicate whether there is any risk of collision.

Another benefit is the much lower radiation exposure to crew who happen to pass through the beam and the near "instant on" with no wait for the magnetron to warm up.

In the end your ability to see small targets is a function of the size array and power within each category. A 200W six foot open array like mine will blow away any magnetron except a 25kW six foot array, to which it is quite comparable in performance. Rather than focus on power, fit the largest array that is within your budget if you want to see small targets at ranges less than 2-3 miles. Better to have a 6kW magnetron with a six foot array than a 25kW with a 3.5 foot array to use an example of magnetron radars. The same is true of the solid state equivalents.

 

[Quitsa]

I wouldn't go through too many gyrations to get a six foot array if you can fit a four foot. One of my main uses for the radar is spotting flocks of birds at a distance for tuna fishing. The six foot is best for those very small targets because of its better target separation. For boats, buoys, land features and most everything else, I don't think there is a meaningful difference. Spotting a lobster pot float 1/2 mile farther away doesn't make much difference. It's not like the difference between a four foot open array and a 24" dome, which is very meaningful.

I looked at the article you cited. There is a bit of marketing hype involved in the manufacturers' discussion of solid state radar. It reminds me of the hype that surrounded the introduction of CHIRP fishfinders. Someone who had a quality conventional non-CHIRP Furuno FCV-1150 and a high performance transducer gained very little spending thousands of dollars to swap for a CHIRP sounder and in fact could end up with a less capable fishfinder.

If there are budget considerations, my opinion would be that a DRS12AX magnetron with a four foot array at $7500 list is going to show targets as well or better than its solid state "equivalent" DSR-12ANXT at $8400 list. You don't have the Doppler shift target display features, it has greater power consumption (important on a sailboat, not so much on a powerboat), and it has a slightly greater minimum range. But it's a great radar as I can attest from five years of using one.

 

[engr_x2]

Right now, because we have a powerboat, I'm considering the DRS12A-NXT because of all the post processing capability that they give you.

On the West Marine blurb, what I didn't realize was the fact of the long pulse and the chirp. What that buys is sampling time from a known frequency output that is varying in a known way. For instance, if you think about a standard magnetron radar, you have to detect a doppler frequency shift of 31.4 Hz per mile per hour speed. That is one part in 3 x10^11 for X-band (if I did my arithmetic right). That is really tough. There is also another theory that says if you analyze a signal over a short time window, you gain good time resolution but have poor frequency resolution, and vice versa. So by increasing the pulse width by roughly 10x, the ability to detect the frequency shift accurately is better. I don't know for sure, but it seems like with the chirp, if how the frequency is changing is known, then you introduce another constraint on your detector to eliminate noise.

Also, I need to check further, but the NXT has both a P0N (conventional) and Q0N mode (aka chirp) albeit the output power is lower.

 

[Quitsa]

I have a DRS25A-NXT and it does not provide for the choice of mode that you described. You seem rather enamoured of the technical features of the solid state radars and the signal processing that takes place. Bear in mind that the current generation Furuno magnetron radars also employ a lot of signal processing technology. As someone with many years of staring at radar displays and a former owner of a DRS12A magnetron, I can tell you the difference on the water is not very significant at all. In fact, there are circumstances in which the short, high powered pulse does a better job of painting targets. I think even the Furuno staff might acknowledge that even though they are supposed to be comparable, the 100W DRS12A-NXT will not do as good a job showing very small targets like birds at longer ranges of 4 miles plus. The 200W DRS25A-NXTwith twice the power is moire comparable to the 12 and 25kW magnetron units.

What you do get with the solid state radars that you don't get with the magnetron is the Target Analyzer mode that uses Doppler shift to paint targets red or green based on CPA and slightly better ARPA capabilities. I don't use the target analyzer mode because I would rather have the traditional radar picture and use the ARPA target vectors and CPA and CPA alarms, which to me are much more informative because the course vector line gives you an immediate visual guide as to the speed of the target.

The other benefit is the somewhat closer minimum range of the solid state radar but in real life is it meaningful? I can't think of too many times when seeing something on the radar 50 feet away makes much difference from seeing it 80 feet away -- two boat lengths in my case -- recognizing that you should have been watching it at a considerably greater distance by the time it is that close and taken evasive action if necessary.

I think it would be great if other people who have used both systems would offer their opinions.

 

[engr_x2]

I very much appreciate your input! For me, it's not a matter of being enamored, rather it has to make technical sense to me (I'm a Maxwell's Equations guy by training) and have relied on others for their experience. I also have a basic understanding of signal processing and signal to noise issues in RF detection. My biggest concern is unmarked obstacles that can inflict more damage than the incremental cost of a more capable system.

My first iteration was to go with high peak power in a 4 ft open array which is what we have now. Works great, but the display is old. What kept me from going that route was the lack of similar post processing comparable to the NXT. But I realize that all the fancy post processing will never overcome brute force power.

It could be that Furuno is trying to migrate people away from the magnetron as I know from my personal experience that vacuum tubes are getting harder to produce because of (believe it or not) environmental laws (volatile organic solvents have been replaced with fancy versions of Simple Green as a degreaser). So getting a vacuum tube to work correctly is more and more difficult. Yields are poor.

So I think you are correct. It would be nice to get some opinions. I'll try the same on some of the yacht forums I'm on.

EDIT: Ep 11 Riding Dragon on YouTube @ about 16:00 min he was able to see Cormorants and dolphins in the water with an NXT/6.

 

[Quitsa]

As I mentioned, I have been running a DRS25A-NXT with a 6 foot array for about five years now. He was marking the dolphins and cormorants at a close range of a mile. The radar can do a lot better than that. Usually I am looking for shearwaters, which are about the same size as cormorants. I can spot them four to six miles away no problem. Dolphins broaching are a big target at a range of a mile and show up well. What is impressive to me is that we get kayak fishermen outside my harbor and the radar will mark the very low to the water plastic kayaks and acquire them as an ARPA target if they are moving.

If you use the radar for navigation, the highest power versions of the solid state radar will do a great job and have some advantage over the current generation of magnetrons because of the Doppler target tracking. But in real life on the water, a 12kW magnetron will also do a great job at the 1/8th to 4 mile range that is most relevant to navigation and I think you would be very hard pressed to find any material performance differences from the high power solid state open arrays.

At the end of the day, there is no substitute for array size and transmission power within each technology. A four foot open array magnetron radar or the high power solid state NXT open array is going to do a better job showing weak targets than any available dome radar whether solid state or magnetron.

One major reason I went with the NXT on my new boat is that the tower is a "marlin tower" where you are standing on the hardtop where the radar is mounted and not on a platform above it as with the full tower on my old boat. That means you are in the radar beam if it is operating so the radiation safety advantage of the solid state becomes important. I wanted to be able to run the radar from the tower occasionally to look for birds without worrying about cooking my eyeballs (or my "lower parts"!) with a 25kW magnetron.