[Moved] Trying to repair old Furuno radar, FRS48

[jensemann23]

I have an old radar Furuno FRS 48 which doesnt give a picture. The sweep is runni g and the scanner rotates. but radar video is missing. does anyone know how to test if magnetron is working? i Also need scematics and service manual, can someone help me with that?

 

[jiripolivka]

Re: Trying to repair old Furuno radar, FRS48

I was also interested in learning details of Furuno radars. I guess the Furuno company only gives the details to authorized repair shops.

One possible advice: while everybody suspects the magnetron to fail first, I would start with the high-voltage supply. In moist environment, this might fail first. Also check the waveguides for moisture and debris.

Good luck!

 

[rodykho]

Re: Trying to repair old Furuno radar, FRS48

check f the filament's heatr has light. give me u add ill try to send u the service manual

 

[BradtheRad]

If the magnetron is what sends out the microwaves, then you can try putting something like food in front of it and see if it heats up.

I once heard a story (secondhand) about a radar operator explaining that there are two radar signal strengths, (1) acquire and (2) track.

Acquire is a low intensity, search mode. When it picks up an unknown, the operators switch to Track mode. It is a much higher intensity.

While in that mode, they have observed birds flying directly in the path of the radar beam. They burst in a flurry of feathers.

I believe that story applied to a military radar. I can't say what your radar would do.

 

[RF_Jim]

If the magnetron is what sends out the microwaves, then you can try putting something like food in front of it and see if it heats up.

I once heard a story (secondhand) about a radar operator explaining that there are two radar signal strengths, (1) acquire and (2) track.

Acquire is a low intensity, search mode. When it picks up an unknown, the operators switch to Track mode. It is a much higher intensity.

While in that mode, they have observed birds flying directly in the path of the radar beam. They burst in a flurry of feathers.

I believe that story applied to a military radar. I can't say what your radar would do.

If true, then, how come no Youtube videos showing same?

Well, truth today must be accompanied by a video ...


Back on topic; a standard AM band transistor radio 20 to 30 feet out from the RADAR will normally detect the 'pulses' from a 4 to 10 kW marine RADAR as the active side of the antenna sweeps by, one will hear audibly the RADAR PRF (Pulse Repetition Frequency), on the order of a few kHz up to 4 or 5 kHz 'buzz'. The longer sweep ranges will have the slower sweep rates on most RADAR, to reduce 'range folding' or range ambiguity at the sacrifice of less target definition.

This is something I have done myself with an old SPS-35 shipboard X-band navigation RADAR.

Jim

 

[BradtheRad]

If true, then, how come no Youtube videos showing same?

Well, truth today must be accompanied by a video ...

I have no firsthand experience so I can't back up the story.

I do find there are discussions about radar beams cooking birds, where the claims bring out comments that go every which way.

Such as at these message boards:

An AEGIS SPY RADAR can cook Turkey - Topic

Radio Antenna Cooking Turkey Episode - Topic



When were microwaves invented

The last link tells how "birds getting too close to the transmitter were cooked." Also about Percy Spencer, who holds the patent for microwave ovens. "He was working on an active radar set when he noticed a strange sensation, and saw that a peanut chocolate bar he had in his pocket started to melt."

 

[RF_Jim]

Thank you for the history lesson Brad. Where would I be without your links and breadth of knowledge.

I checked the first link you posted above, about the Aegis s p y RADAR, and the opinion appears split as to yes-it-can or no-it-can't.

What I didn't find either was any maths, from either side, to support their contentions.

Note even one quote as to what the energy density is in a microwave oven vs the calculated energy density in front of a large phase-array RADAR.

What was thrown about were 'peak' power numbers, not to be confused with average or "RMS" power numbers even; and as we all should know (from our basic physics classes) is that it is the RMS (Root Mean Squared) or 'effective DC heating power' which indicates the amount of 'work' (or heat in this case) can be done.

Nor was it explained that the energy emanating from the Aegis RADAR is emitted from across the areal surface of the antenna, not just a single spot, in order to form a planar (as opposed to spherical wave, which would be the case with a point source antenna) EM wave in a more or less single 'column' (or conic section, like a megaphone) with a specific beamwidth, and which subject to the laws of physics, is subject to divergence at distance and whose power density impinging on a surface at some distance (like a bird) is proportional to the inverse square of the distance ... what this means is double the distance from the RADAR and get 1/4 the power. Double again and you're at 1/16 the power and so on ... do you recall this from physics?

Jim

PS And still, without a YouTube video it's all still just 'hearsay'. You do get the irony of this don't you?