MARINE RESCUE PROCEDURES

terça-feira, 28 de janeiro de 2014

MARINE RESCUE PROCEDURES
During normal radio operation on any band, there is the possibility of an amateur radio operator coming across an emergency call or a distress call from a ship or yacht at sea. How does one handle a situation where loss of life is a possibility ?
There are three types of calls one could hear. Two of the calls are distress calls and the 3rd a call for "getting your attention" - not necessarily a ship or yacht in distress.

DISTRESS CALLS
There are two levels of distress calls, Pan Pan Pan and MAYDAY.
The third call is "Securité".
All above words are derived from French words or expressions.
Let's handle the calls one by one.

PAN PAN PAN.
A Pan Pan Pan call is used when there is no immediate threat to the vessel concerned, although assistance is almost always going to be required. As an example! A vessel that may have lost power or a mast and may be drifting with no means of control. Man overboard is another situation where Pan Pan Pan is generally used.

Your formal response to a Pan Pan Pan call is:-
"Pan Pan Pan (vessel name)" - repeated three (3) times;
"This is (radio station XYZ), received your Pan Pan Pan"
Confirm reception and signal report.
The questions that need to be asked after making contact with the vessel are handled under MAYDAY, as this set of questions applies to both situations.

MAYDAY.
Let me stress at this point - a MAYDAY call is a very - very serious call and a
very serious situation!
The MAYDAY distress call is used when the vessel or aircraft concerned are in grave and imminent danger, and require immediate assistance.
Your formal response to a call MAYDAY is:-
"MAYDAY (vessel name)" - repeated three (3) times;
"This is (radio station XYZ), received your MAYDAY"
Confirm reception and signal report. Once confirmation of a good contact has been acknowledged, the following procedures should follow:-
Establish the following:
1. Vessel name/type/description - e.g. size, motor driven or sail, ski-boat etc. If a large maritime ship - the IMO number - i.e. the International Mar i time Organisation number. If necessary, get the spelling of the name of the ship or yacht phonetically to ensure accuracy.
2. Location - Latitude/Longitude. Be very careful to get an accurate position!
3. Nature of problem. What is the nature of the current situation!
4. Last port of departure. Also where is the vessel headed!

Should you require backup communications or assistance, you may wish to call Alistair Campbell, ZS5MU, on 039-684-6421. Alistair runs the South African Maritime Mobile Net starting on 14.316 kHz followed by 7120 kHz at 06:30 and 11:30 UTC daily.
Alternative call is Graham Griggs ZS2ABK at 046-648-1071 (Cell 083-756-0288) or Francois Botha ZS6BUU at 083 585 3847 or Graham Hartlett ZS6GJH at 082 441 6989.

At this time it is best to contact the Maritime Rescue Co-ordination Centre (MRCC) on
021-938-3300 for further instructions. Alternatively, use the number 082911.

Additional information, which may be useful in the event of a maritime rescue, but which should only be asked for as required by MRCC, is:
1. Name of skipper/master; it is essential that the name of the person who makes the final decisions, name is available and known!
2. Intentions of the skipper/master; Very, very important. The Master or skipper of the ship or yacht must very clearly to state their intentions in no uncertain terms!
(Those "intentions" meaning - "we are about to abandon ship and need your assistance" - or "we have a rescue tug on its way and need you to stand by" - or "we have instructions to remain on board", etc.)
3. How many persons on board;
Availability of life jackets, life rafts , flares, portable or fixed VHF radios and a
EPIRB beacon - and if possible, the EPIRB NUMBER.
4. Weather conditions and the known proximity of other vessels in the immediate area.
All communications with Maritime stations ought to be kept short, concise and factual as operating conditions almost always preclude lengthy QSO's.

Lastly, the SECURITé call.
This could be from 2 sources - a ship at sea or from a station on land indicating a warning to all shipping.
From a ship at sea the call could go to all other shipping in a specific area that there are containers that fell off a ship and floating in shipping lanes that could cause damage to other shipping. Or even logs that have been washed out to sea and in a normal shipping lane.
Alternatively, the call could come from land based shipping monitoring radio stations with a warning of severe weather in an area that Skippers or Masters should be aware of.

Finally, should you ever become involved with ANY shipping emergency and you feel you need assistance; don't hesitate to call for assistance. Above all, know what you are saying and par ticularly, ensure what you are hearing and have to convey to a third party, is accurate and clearly understood.
I would go so far to say, that if you need to convey (patch) an emergency message via phone, cell phone or from someone on the ship via amateur radio - even if this person is not a licensed amateur radio operator - you will not be taken to task; PROVIDED you submit a FULL AND DETAILED report on the incident to the SARL who will inform ICASA.
NEVER make assumptions. You could be the cause of loss of life at sea and the legal consequences are something you don't even want to have a nightmare about!

Source: Hamnet KZN

Interference on SSB radios

Interference on SSB radios

Reducing radio interference

Jul 14, 2015

BY HARRY HUNGATE

Radio frequency interference from your refrigeration compressor could be affecting your SSB radio.

It sounds like a crude form of Morse code on your single sideband transceiver. The interfering signal is strong enough to disrupt fax reception, render voice reception unintelligible and bring your onboard email to a halt. It seems to occur all across the bands, stronger on some frequencies, weaker on others. If when you turn off your 12-volt refrigeration the interference stops immediately, read on — this newsletter is for you.

The culprit is the electronic control module (ECM) on the compressor of your refrigeration unit. Danfoss manufactures the direct current hermetic compressors and electronic control modules for almost all of the world’s suppliers of small, direct-current refrigerators and freezers. Over the years they have changed the design of the electronic control module several times, adding better shielding, but to date they are still a long way from achieving an interference-free product. The ECM does a dandy job of driving the compressor and can also jam your SSB radio.

You could just switch off your refrigerator while using the radio, but if you forget to switch the refrigerator back on just once, well, need I say more?

A number of steps can be implemented to reduce, if not totally eliminate the interference. The first step is to inspect all of your radio grounds. The interfering energy must be diverted to ground and without a clean ground, success is not likely. Radio frequency energy flows along the surface of the conductor. Salt water rapidly corrodes copper, forming copper oxides that create a high impedance path to radio frequency energy. Replace any copper ground foils that appear to be corroded and thoroughly clean the connections. Coat the cleaned connections with silicone grease.

Conducted and radiated interference
The second step is to track down and identify the various paths of interference, of which there are two types: conducted and radiated. While the interference is created within the ECM itself, it is the connecting wiring and even the refrigerant tubing that acts as radiating antennas. Conducted interference travels from the ECM to your radio via the power wiring, and radiated interference travels through the air entering your radio via the antenna. To complicate matters even more, radiated interference can enter the various wires and cables connected to your radio. Most probably you will have to treat both conducted and radiated interference to achieve an acceptable reduction in interference.

A most effective tool to identify radiating items is a “sniffer” made from a length of RG-58U 50-ohm coaxial cable, the 1/4-inch (6 mm) diameter coax. The sniffer is actually a small directional antenna. The American Radio Relay League’s RFI Book shows how; you will need a length of coax sufficient to reach from your radio antenna connector to the compressor and to the battery bank, plus an extra foot or so (330 mm). Install a coax connector (typically a PL-259) that will fit your radio’s antenna connector on one end of the coax. On the other end remove 1.5 inches (36 mm) of the outer insulation jacket and braided shield, and then remove one inch (25 mm) of inner insulation from the end of the center conductor. At about 12 inches (305 mm) from the end of the coax, score the outer insulation and pull it back about 1/4 inch (6 mm) to expose the braided shield. Holding the end of the coax, form a coil of three turns about two inches (50 mm) in diameter. Wrap and solder the inner conductor at the end of the coax to the exposed shield. Use vinyl electrical tape or heat shrink insulation to cover the joint and to hold the coil together.

Using the sniffer
Prop open your freezer lid or lower the thermostat setting to make the compressor run constantly. Turn on your SSB radio and tune around for a strong interference signal. Disconnect the antenna coax from the radio. A significant reduction in interference should be noted (with the antenna coax disconnected, the reception of radiated interference is greatly diminished, and any interference noted will be conducted interference, entering the radio via the power cables). Connect the sniffer to the antenna connector on the radio and pass the loop over the compressor, refrigerant tubing, thermostat wiring and power wiring, noting changes in the interference signal. The coil provides directional sensitivity, with the flat side of the coil being the most sensitive. Make a list of the offending items.

Close the freezer, reset the thermostat to its correct setting, reconnect the antenna coax and store the sniffer for later use. Review your list of offending items and apply the following fixes, beginning with the item that is the strongest source of interference. After each fix, turn on your radio and make a note of the change (hopefully a decrease) in the interfering signal.

Strip the outer braid or shield from a length of coax and use the braid to connect the chassis of the compressor unit to the ship’s ground. You should use marine grade RG-213/U coax since the shield or braid is tinned and will not corrode as quickly as bare copper. Use crimp terminals on the ends and keep the length to a minimum; i.e., do not coil up any excess.

Refrigerant tubing: Again, using the outer braid from coax, make four or five wraps around each tube and connect the other end to the compressor chassis at the ground connection made in item one. Again, keep the length to a minimum.

Power cables: Replace these with RG-213/U coax (the 1/2 inch or 10 mm diameter type.) The RG-213/U coax has a 0.7-mm diameter inner conductor, much larger than the more common RG-8/U coax, so it will carry more current with less voltage drop. Allow for enough braid on each end to be connected to ground and keep the braid over the center conductor as close to the ends as possible without causing short circuits. Use heat shrink insulation to prevent short circuits. Always twist power cables a minimum of one twist per twenty-five cable diameters to cancel out interfering currents.

Thermostat wiring: Chances are that any excess thermostat wiring has been formed into a coil and secured near the compressor, as per the installation instructions. Your tests with the sniffer will have revealed this to be a prime radiating antenna, so simply cut out the extra wire and rejoin the ends. Install ferrites (either snap-on or toroids) on each end.

Construct a Faraday shield over the compressor unit. Galvanized steel sheet of 0.22 inches (0.56 mm) minimum will serve nicely. Begin by cutting out two sides, the top, and one end. Provide openings for the refrigerant tubing, thermostat wiring and power cables. When assembling the box, allow for overlapping seams of 7/8 inch (23 mm) minimum. Soldered seams are the most effective, but pop rivets may be used. Space them no more than two inches (50 mm) apart. Also, 3M makes an adhesive-backed EMI tape that can be used to seal the seams. Sealing the seams is particularly important, so don’t just cover the seams with duct tape. Fit the box over the compressor unit and hold it in place with duct tape. The condenser end of the box is effectively shielded by the condenser and the bottom of the box is the metal chassis of the compressor/condenser unit. Seal around the wires and refrigerant tubing entering the faraday shield with “donuts” made from at least two layers of metal mesh (bronze screen wire is good for this purpose).

Bypass capacitors
Install bypass capacitors from the power cables to ground. Use 0.5 µf 25 v (0.5 microfarad 25 volt) disc ceramic capacitors in parallel with 220 µf 25 v NPO electrolytic capacitors. If you replaced your power cables with coax as in item 3, then simply solder the capacitors to the inner conductor and braid, keeping the capacitor leads as short as possible. Use heat shrink insulation on the capacitor leads to prevent short circuits. The bypass capacitors act as short circuits to interfering signals, but act as open circuits to direct current.

Install an alternator noise filter in the positive power lead to the compressor. Be sure to connect the ground terminal on the noise filter to the common ground point on the compressor chassis.

A last desperate step, which should only be attempted if your electronic skills are top notch, is to install a speed controller on your compressor. The idea is to shift the speed of the compressor and thus the frequency of the interfering signal away from your SSB radio operating frequency. The ECM determines the operating speed of the compressor by measuring the resistance in the thermostat circuit. By replacing the fixed resistor in the thermostat circuit with a potentiometer mounted where it can be reached from your radio operating position, it will be possible to “tune” the interference either below or above your operating frequency. Only a couple of hundred revolutions per minute change in the compressor operating speed will be required, and will have negligible effect on the operation of your refrigeration system. In the installation manual for your compressor locate the schematic for the compressor and ECM. On the schematic, determine the physical location of the speed resistor. A chart will show various values of resistance versus compressor speeds. For instance, if the chart shows 1,500 ohms resistance for 3,000 rpm, replace the 1,500-ohm resistor with a 1,200-ohm resistor and install a 500-ohm potentiometer in series in the thermostat circuit.

To treat conducted interference, install ferrites on the radio power cables. These can be the snap-on type, which should surround both positive and negative power cables, or the toroid type. The more turns through the ferrite, the better the interference suppression. Multiple ferrites may be required. Ferrites act like electronic tourniquets by absorbing the interfering energy and preventing it from continuing along the conductor. Use type 43, 75, or J ferrites. Ferrites may be purchased from www.digikey.com and www.jameco.com and www.amidoncorp.com.

A follow-on item, not related to interference, would be to insert some air conditioner filter media around the sides and top of the Faraday shield at the condenser. This will trap dust and lint that would otherwise clog the fins in the condenser, leading to a drop in efficiency.

Despite your best efforts it may not be possible to completely eliminate the interfering signal, but at least it can be attenuated to an acceptable level.

Harry Hungate is an extra class ham radio licensee (N1UDE/ZL1HAH) and also holds the FCC GROL with radar endorsement. He and his wife Jane completed a circumnavigation aboard Cormorant, their Corbin 39 cutter.

Ideias as installing HF antennas.

How to resolve interference SSB Radio
http://www.lereseauducapitaine.qc.ca/PDF/HF_Radio_marine.pdf