Thursday, November 9, 2017

Radar Troubles

Radar not working

We're preparing for some night sailing this winter and the Admiral really would like to get used to using the Radar. Luckily, I serviced helicopter Radar systems during my 25yr Navy Career and feel very comfortable using and teaching the concepts and practicalities of a Radar System.

But, the Radar has to work - right! It seems that the Radar system in Eximius suffered during the visit by Hurricane Irma. The Radar systems that I serviced in the Navy had multiple components, but that was 30 years ago. Today the Radar consists of a Radome that has all of the Radar equipment contained in a single unit with an output to our Chart Plotter which also controls the functions of the Radar.

The Radar System has it's own power supply via a Circuit breaker on the main Electrical Control Panel but it's operation is managed via the GPS Map 741sx (our Garmin Chart plotter). We're getting Low voltage warnings on the GPS whenever the Radar is powered up and we're not getting the control options - so there's something not working (or was we said in the Navy - It's US - UnServiceable)

So time to do some fault finding.
  • Check that the circuit breaker is Serviceable
  • ..Use Multi Meter to check the Power on the output side of the Circuit Breaker - 13.8 Volts.
  • ..Power is ok at the breaker.
  • Check the power at the Radome
  • .. detach the Radome from the mounting plate
  • .. Disconnect the power cable from the Radome
  • .. Use Multi Meter to check the voltage at the cable end - 13.6 volts
  • .. Power is ok, 0.2v voltage drop, that's pretty good for a 48' cable
  • Check the supply wire resistance (voltage drop will increase when the current flow increases)
  • .. +ve Wire - 0Ω
  • .. -ve Wire - Wow! off the scale!
Contacted Garmin Tech support and they concur - supply cable looks very suspect.

I decided to order a replacement cable and test it before routing the wires inside the boat.

Good news - Garmin will allow me to return the cables within 30 days if they don't solve the issue (which means that we'll have to ship the Radome to Garmin for repair 😖 )

So, armed with that good news, I also ordered a replacement for the Cat 5 Cable that runs from the Radome to the Chart Plotter as both cables run together from the Radome, outside the Radome Mounting pole and then into the deck, currently via a nasty blob of Silicone caulk which will have to go.

New cables should arrive in 2 days.

New Cables Arrived

Garmin came through! The new cables arrived via UPS yesterday (Wednesday), so, today we headed down to the boat to test the Radar using the new Cables.

I decided to test using the old Cat 5 Cable but the new Power cable as it was the high resistance in the power cable that caused me to get the new cables.

Disconnected the old Radar Power +ve cable from the Circuit Breaker.
Connected the new Power cable +ve to the Circuit breaker
Connected the new Power cable -ve to the ground bus bar inside the Electrical panel.
With the Radar Circuit breaker turned off, we flashed up the Chart Plotter (Garmin 741xs) and confirmed that the Radar did not show up in the list of System Devices - it did not.
Turned the Radar Circuit breaker on, and we could immediately hear the Radome making noise, that was a good sign. But nothing on the Chart Plotter. I was about to check the connections when the noise from the Radome dropped significantly. At that point, the System devices showed the Radar. Getting somewhere.

To test the Radar, we accessed the Chartplotter home screen and selected Radar - It now shows that it's ready to Transmit with the 'Transmit Radar' option. Selecting that option we could hear the Radar spin up and the display indicates that it is 'Spinning Up' Looking good.

After a few moments, perhaps a minute, we navigated to the Home Page and Selected Radar - it now shows 'Radar to Standby' which indicates that it's currently transmitting, we selected 'Cruising' mode and the screen quickly displayed a typical radar screen, we changed the range to 1/4mile and could clearly see the echos from targets along the sides of the canal ahead and astern of us. WoooHooo! 

View of the Radome from astern

There're indicators on the Radome that provide orientation, the two small ones in the top right hand side of the pic show the Aft Center of the Radome

The Radome is mounted atop of a Steel tube (not Stainless as can be seen from the rusty surfaces) with a Steel plate on top. 
The lower end of the tube passes through a hole in the deck outside of the cockpit and then down, inside the aft locker to a plate that is screwed to the hull. I know, WTF! Why didn't the installer use Stainless Steel and why didn't they make it a deck stepped tube, and why didn't they run the power and Cat 5 cables inside the tube?

Danged if I know, but I'm looking into what it would cost to have a new Radar Support Tube, plate and lower flange manufactured. If the cost is reasonable, I'll have it made and re-work the entire Radar Mounting system.
The pic also shows the Eye bolt in place of one of the securing screws, attached to that eye bolt with a shackle is our Outboard Engine hoist block. Also on the underside is an Aluminum angle bar that can be used for an Antenna, so I'll be hooking one up to that for our SSB Receiver. That should improve SSB reception.

Having confirmed that the Power cable was the problem, I started the change out process. Another install screw up. The original installers had run the 48' of power cable wire down through a hole in the deck, along with the Cat 5 Cable, then both were coiled up and strapped to existing tie wraps in the aft locker just ahead of the Aft Water tank. Then they had crimped a pair of 16awg wires to the ends of the power cable and run those to the main electrical panel - via two different routes. Duh! The 48' of cable is probably about 15' to 20' too long! So they could have just run the power cable to the electrical panel and cut off the excess - that would reduce the voltage drop along the length of the wires and eliminate at least two cable crimp joints! Guess what I'm doing? - Yep, run the new line to the electrical panel and cut it short before connecting it to the Circuit Breaker and Ground bus bar.

I had to go to West Marine to pick up a Blue Sea Cable Clamp as I don't want to have another lump of silicone caulking where the cables pass through the deck. If I do replace the Radome Mount, I'll run the wires through the inside and repair the deck where there are currently two holes, one for the tube and the other for the wires.

At least I'll get it back to fully working status tomorrow - Friday.

Might even get out for a sail as we had hoped.

See you on the water.


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