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Aquah0lic · 23-11-2008, 14:58

I picked up a little JRC 1000 despite being warned about JRCs because it was cheap and I got to see it work on my neighbors boat. I would like to mount it about 15' up on the mast right above the first spreaders where the steaming light is and attach the light to the mount. Can I buy a mount like this somewhere or should I be looking to have something fabricated locally?

Also, I'd like to run the cable inside the mast using(or enlarging) the existing hole and make a new hole in the mast after it comes through the cabin roof to route over to the nav station. Any tips on drilling the new mast hole? How do you stop water from in the mast running out on the cable?

Aquah0lic · 23-11-2008, 15:11

A related question... I have isomat spars with internal halyards. Are they in some kind of conduit or hanging free and will the cable interfere with them?

Hampus · 23-11-2008, 15:53

Hey!

I spent more than two years working for the local JRC-dealer, installing and servicing their equipment. I've installed JRC-1000s on leasure boats as well as the JMA-99XX and various other RADARs on larger ships. I've also installed and serviced most of their other products. As with any other brand there are pros and cons with JRC, but I don't know why you were warned about the JRC-1000. It has obvious limitations because of the size of the scanner, but so would any RADAR that size. It is excellent value for money and it does the job without any problems. JRC are really big on components if you open any other make of RADAR and look at the components, chanses are you'll find something that has "JRC" printed on it. Up until 1996? JRC and Raytheon were pretty much the same company and up until that time most of the parts of the Raytheon and JRC radars were interchangable (similar models).

The JRC-1000 is a pain in the b**t to install, regarding the size of the plug on the cable and the fact that it's quite difficult to remove the cable from the scanner. Other models like Raymarine have solved this by putting small contact on the scanner side of the cable and have you hook it up after the cable is run. our solution was often to bring out the big wire cutter and cut the cable close to the plug (not too close though, it's difficult and tight to solder). Then we'd run the cable and make a soldered joint, or just use a connection box to connect the two ends. Worked great as there is no high frequency signals in there, just data and analogue video.

As for the mounts we'd buy from third party manufacturers. I can't remember if JRC has one and the JRC-1000 is out of production. Custom made or third party and modify would be your best bet.

/Hampus

Aquah0lic · 23-11-2008, 17:32

Hey thanks for the reply. Considering your experience with and installing these units, does my plan above look good? I could use some pointers as I am still pretty rough around the edges on my boat skills.

Hampus · 24-11-2008, 00:05

I usually advise people not to put their radars in their masts. There are advantages ofcaurse, like less obstruction in front of the radome. You will also get more range on most radars although with the JRC 1000 the range is more limited by the small size of the radome than by the mounting height. The cons are: More movement in the mast, big leaking holes in the mast for the cable, it's really hard to make them watertight and with the JRC-1000 there would be BIG holes if you don't cut the cable. Every time you take off the mast (every winter up here), you need to pull the cable from inside the boat, unless you have an easy access connection by the foot of the mast. If you do put it in the mast, a custom made mount would be the best option.
There is always some movement in the mast and keeping any sealing watertight is quite difficult. Running the cable outside the mast and using something like a "Cableport 12" through the deck is the best way. Besides, those big holes will weaken the mast.

Aft pole mount is what I usually recommend and the pros are: Easy access for service, there are mounts that let you tilt the radome to keep it horisontal as the boat heels over. Easier installation. You can mount lots of other stuff on the pole as well and you give the seaguls a place to rest

Cons: Obviously you have an ugly looking pole in the aft and the mast will give you around a ten degree blind sector. Those poles are usually so expensive you'd think they're made out of pure gold. It's not that hard to make one yourself if you're a bit handy with the tools though.

If you do mount it in the aft, remember to plece it on the starboard side. That would put your blind sector more on the port. The only reason for this is that ships coming from your starboard side (at least while on engine) have the right of way.

/Hampus

Tempest245 · 24-11-2008, 16:53

Not sure if this is the correct tread/forum for this.

I'm thinking of adding radar this spring. My yard owner suggested that I mount a 2kw unit on the backstay. (34 sloop )
I'm guessing that a rear facing mount would eliminate any chance of the mainsail leech or the topping lift interfering with the setup.

Does anyone have reviews/advice on this style of radar installation.

I see that they have gimballed mounts, Questus is one, Scanstrut (sp) is another.

My Backstay is used for the SSB antenna, would mounting a radar dome cause problems ( interference) with the SSB?...

I'm not keen on a big pole stern mounted, and the mast mount concerns me with regard to sail chafe on the roller furling jib. Looking for advice/experiences/opinions.

Thanks,

Tempest

Hampus · 25-11-2008, 12:06

Quote:

Originally Posted by Tempest245

Not sure if this is the correct tread/forum for this.

I'm thinking of adding radar this spring. My yard owner suggested that I mount a 2kw unit on the backstay. (34 sloop )
I'm guessing that a rear facing mount would eliminate any chance of the mainsail leech or the topping lift interfering with the setup.

Does anyone have reviews/advice on this style of radar installation.

I see that they have gimballed mounts, Questus is one, Scanstrut (sp) is another.

My Backstay is used for the SSB antenna, would mounting a radar dome cause problems ( interference) with the SSB?...

I'm not keen on a big pole stern mounted, and the mast mount concerns me with regard to sail chafe on the roller furling jib. Looking for advice/experiences/opinions.

Thanks,

Tempest

Hey!

I don't know the questus, but the Scanstrut makes excellent hardware. They also have really nice poles. Mounting your RADAR on the aft stay probably won't cause interferrance with the SSB. The SSB might fry the radar though. High frequencies and high effect might damage circuits even if not in direct contact. i'm not saying it will, but I would never have mounted it there.

/Hampus

zeppelin · 25-11-2008, 12:58

We put a new radar on our mast 2 years ago similar to what you are proposing. There is an excellent mast mount made by Seaview, it is universal to all masts due to articulating feet and they have one that will fit the JRC 1000. Seaview also makes all sorts of poles and backstay mounts as well. West Marine carries their product as do others I'm sure.

The halyards in your mast will not likely be in a conduit however all your wiring should be, otherwise the halyards will chafe through the wiring when hoisting sails up and down. The biggest challenge will be to get the radar wiring into your existing conduit and down the mast, especially with the mast in the boat. You may also have a problem with the plug being too big and not fitting into the conduit, not to mention the size of the hole in the mast to run it through. The options being disconnect the wiring inside the unit if possible and pull the wire up the mast with a tracer line or cut off the plug as described in the earlier post and then reattach it.

To deal with the water issue you could have the cable exit the mast above the deck, and have it go through a watertight cable fitting beside the mast, Blue Seas makes good ones, and then over to the nav station. If you then rewire the plug by using a junction box it is easy to disconnect the wire and pull it back up through the watertight fitting if you ever have to pull the mast.

Hope this helps.

gettinthere · 26-11-2008, 05:15

installed a garmin radar on the mast this spring. used a rubber grommet with sealant to seal the wire going out of the mast into the radar.
Bought Seaview radar mount for Garmin. They have several variations to cover different configs.
Keel stepped mast with hole below deck where radar wiring comes out of the mast.
Added RJ-45 jack here to plug/unplug wire when stepping/unstepping mast.

RBEmerson · 26-11-2008, 07:22

A big con for aft mounted radars (backstay or mast): zapping anyone on the cabinhouse. Most non-mast mounted radars are low enough that anyone standing on the cabinhouse is probably squarely in the beam from the antenna. While it's not likely that any one exposure will do signifcant damage, the effects are cumulative and are significant; by way of example, a doctor friend did a study on testicular cancer in troopers who kept their radar guns in their laps - it was not a happy report. Additionally, with the exception of those backstay mounts that use a torque tube around the back stay (only one such maker, IIRC), the directional stability of backstay mounted radars is, to be blunt, laughable.

Most radars' interconnection cables (the one from the scanner to the display) are thick enough to discourage internal halyards from wrapping around the halyard or vice versa. Seaview provides a gasket for the 1" dia. hole needed by the cable. Between the gasket and a lot of caulk, I wouldn't lose too much sleep over mast leaks.

amytom · 26-11-2008, 08:05

Radar is non-ionizing radiation so it is NOT cumulative. Radar only heats the water molecules based on the power level and duty cycle. With an aft mounted 2Kw radar a person standing on the coach roof is getting more radiation from the sun on a cloudy day than the radar.
Now standing directly in front of a military high power radar would be a different story.
The biggest concern with aft mounting would be the lower altitude (less range and more sea clutter) and the blind spot from the rigging.
I did mount mine on the mast and the worst of it was running the cable down inside the mast while hanging in the chair. (Why don't the mast trunk and compression post ever line up with the whole in the deck?)
As for maintenance, what maintenance can you do while underway? Without special test equipment, o'scop, spectrum analyzer, freq counter, etc...) the only thing you can do is replace the belt.

Hampus · 26-11-2008, 09:41

Quote:

Originally Posted by amytom

Radar is non-ionizing radiation so it is NOT cumulative. Radar only heats the water molecules based on the power level and duty cycle. With an aft mounted 2Kw radar a person standing on the coach roof is getting more radiation from the sun on a cloudy day than the radar.
Now standing directly in front of a military high power radar would be a different story.
The biggest concern with aft mounting would be the lower altitude (less range and more sea clutter) and the blind spot from the rigging.
I did mount mine on the mast and the worst of it was running the cable down inside the mast while hanging in the chair. (Why don't the mast trunk and compression post ever line up with the whole in the deck?)
As for maintenance, what maintenance can you do while underway? Without special test equipment, o'scop, spectrum analyzer, freq counter, etc...) the only thing you can do is replace the belt.

You are absolutely right. The radiation is not cumulative. It is microwave radiation, same as from your microwave oven and quite similar to that of your mobile phone, although slightly different frequency. An example; The following specs are taken from the small Furuno M-1623. A radar for small leasure boats. It has a 2.2 kW magnetron (2200 Watts). Quite similar to the 2 kW JRC previously mentioned. On ranges between 3 - 16 Nm it will use a PRF (Pulse Repetition Frequency) of 600 i.e. it transmit 600 short bursts every second. Each of those bursts has an effect of 2,2kW. The duration of each pulse (pulse length) is 0.8us (0.8*10^-6). To calculate the avarage transmitted effect we do the following: PRF * Pulselength * Effect and get (0.8*10^-6) * 600 * 2200 = 1.056 W

The avarage effect is only 1.056 Watts, and that's only if you hug the radome. Same as your mobile phone (2 watts on some networks). Most of you, myself inculded keep the mobile phone in your pockets where it will keep you goodies nice and warm

You will pick up more radiation speaking in your mobile phone, sitting too close to an old TV, standing within 3 feet of the microwave or spending a day in the sun than you will from standing next to a 2.2 kW radar. The safety distance of a standard 10 kW x-band radar mounted on most merchant vessels is 3 feet. Translates into: "Don't get hit in the head by the antenna!"

/Hampus

RBEmerson · 26-11-2008, 13:18

I stand by my comments. However, to be quite clear, I do not think and I do not want to imply that standing in front of a transmitting marine radar, on essentially a one time basis, means significant, irreversible damage is certain to occur. Nonetheless, the effects are cumulative in the sense that a few cells damaged here and a few cells damaged there eventually leads to detectable damage. Standing in the beam at the distances obtained between a deck-mounted radar mast and the boat's cabinhouse is just plain unwise.

Additionally, while smaller 2 kW radars are common, 4 and 10 kW radars are not out of the question. For example, the JRC-built R20X formerly on OWTW and the present R70+ both have 4 kW transmitters. Further, I was recently on an aluminum-hulled sailboat with an open scanner on a radar arch. I don't know how powerful that radar is but 10 kW in open scanners is common.