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Marine MF/HF system

This page should give you a guide on installing an MF/HF (SSB) transceiver on a average size yacht.

M802 system overview



MF/HF (SSB) Installation: Getting it right!!!

There are 3 main parts to an marine MF/HF installation:
  1. The Power Supply
    An MF/HF (SSB) transceiver requires peak currents of 25 to 35 Amps, depending on transceiver and power output. Hence the voltage drop between the power source and the SSB transceiver should be no more than half a volt.
  2. Good ground
    For any MF/HF radio system to work a good connection to ground or salt water is required. On a steel yacht this is not a problem. On a plastic yacht you need to mount one or more 300mm by 75mm ground plates to the outside hull of the yacht and connect them to the ATU with 50 mm by 0.5 mm copper strip.
    Keep the antenna grounding system completely separate from the DC or electrical grounding system.
    Inside the hull internal grounding such as wire mesh or inductive paint and KISS-SSB do not work well on low frequencies, as they can induce RF current into the boats electrical systems.
  3. The Antenna
    The antenna MUST be kept clear of other cables and electronic equipment.
    The start of the antenna is at the ATU, so mount the ATU well clear of other electrical equipment and cables.
    A 7 metre long marine whip antenna works best as it gives vertical polarization which is good for long range communications on higher frequencies, 8MHz and above depending on the whip length. The backstay can be used if properly insulated and a good RF connection is made. Due to the length of the backstay, performance is usually better than a whip on the lower frequencies, 2 MHz and 4 MHz.
    Try and keep the antenna well clear of any metal, including bottom section of backstay.
    The ATU can produce some very high RF voltage which can cause burning if touched. It is therefore highly recommend that an high voltage weatherproof single core cable is used between the ATU and the antenna such as GTO-15.

Marine MF/HF (SSB) antennas

Whichever antenna you are going to use, backstay or whip, this page is intended to give some hints on how to get the best performance.

First thing to consider is that your SSB antenna is like a musical instrument, if you want to sound good (transmit well) then you must get it right. Although it may receive stations does not mean that it will transmit or radiate well.

The antenna starts at the top of the ATU (antenna tuner unit) and ends at the top of the antenna, if using the back stay then top insulator. Therefore the cable from the ATU to the antenna itself is part of the antenna and it is recommended that a high voltage cable is used. It is not practical to get an antenna system on a yacht to work across a wide range of wavelengths. An MF/HF SSB works on a wide range of frequencies (2 MHz to 25 MHz) and therefore wavelengths are between 12 metres to 150 metres.

An antenna which works on 12MHz may not be so good on 2 MHz.
A good antenna on 2 MHz is harder to achieve due to the long wavelength of 150 metres but may not be effective on 12MHz due the multiple wavelength of 6 wavelengths.
When considering the antenna system, decide what frequency you are going to use the most and optimize the antenna for that frequency.

Avoid multiple wavelengths or half wavelengths as the ATU may have problems tuning to these frequencies.
If the antenna length is 15 metres long then the ATU should tune across a frequency range of 1.6 to 25 MHz with no problems.

NOTE: The antenna on an SSB systems starts at the Antenna Tuner Unit (ATU) !

Yacht Communications



Insulated Backstay Antenna for Yachts.

The backstay can be used as an antenna, if properly insulated and a good RF connection is made to it.
Due to the length of the backstay, performance is usually better than a whip on the lower frequencies (2 MHz and 4 MHz).
Try and keep the antenna well clear of any metal, including bottom section of backstay.
  1. Mount top insulator at least 1 metre or more from top of mast.
  2. Mount bottom insulator close to deck level.
  3. The antenna length, from top of ATU to the top insulator, should be no shorter than 7 metres and no longer than 15 metres.
    1. To avoid half wavelengths on marine frequencies, the antenna length should be no longer than 15 metres.
    2. If antenna longer than 15 metres then ATU may have problems tuning the antenna on higher frequencies.
  4. Stand the antenna cable from the antenna tuner to the backstay off uninsulated backstay or other metal by 75 mm using some plastic tubing and secure with cable ties.
    1. Keep antenna as far away from other cables and metal objects as possible.
  5. Use a high voltage weatherproof single core cable between the ATU and the antenna, such as GTO-15.

NOTE: The antenna starts at the ATU and therefore the antenna is between the ATU and TOP insulator of the backstay!





Bottom Section of Backstay

BackstayInsulated Backstay, if done properly a backstay can make a very good SSB antenna.
Connection to backstay:
The weakest electric link in any backstay insulation, is the connection to the backstay.
Keep the connection clean and do look from time to time for corrosion.

Depending on the frequency, you may loose transmit power if you do not stand off the antenna cable from the bottom backstay section.

It is highly recommend that an high voltage weatherproof single core cable is used between the ATU and the antenna, such as GTO-15.

NOTE: The antenna starts at the ATU and therefore the antenna is between the ATU and TOP insulator of the backstay!

Yacht Communications


Standing antenna cable off the bottom of the backstay
BACKSTAY


Icom M802

The Icom M802 MF/HF transceiver from SailCom Marine comes programed with all UK coastguards MF frequenices and MMSI number along with European simplex frequencies and DSC ship to ship frequencies.
But only from SailCom Marine http://www.sailcom.co.uk/m802

IC-M802

Phone: 01489 565100
Overseas: 00 44 1489 565100
Email Address - click here!


Dynaplates

A good antenna system requires a good ground, on a yacht this means having a good connection to salt water. On the fiberglass yacht this is achieved by fitting 1 or 2 ground plates to the outside of the hull which is always under the water line.

A good quality Dynaplate should be used, good quality Dynaplates have lots of small holes in them allowing sea water to seep into them increasing the suffice area and therefore giving good contact with sea water.

To reduce drag the Dynaplate should be mounted flush to the outside hull of the boat with no gaps showing else weed and small animals get caught in the gap which can increase drag on the yacht.

The Dynaplate should then be connected to the antenna tuner unit (ATU) by means of 50 mm copper or wider strip copper strip. The length of the copper strip should be kept as short as possible. To reduce possible RF earth loops, the Dynaplate should NOT be connected to any other part of the SSB or boat electrical system.

dynaplates

Click here to order your Dynaplate

GMDSS radio course for yachtsmen
All you need to know about marine radio

LRC Radio
http://www.yachtcom.co.uk/lrc

Phone: 01489 565100
Overseas: 00 44 1489 565100
Email Address - click here!


KISS-SSB Counterpoise HF Radio Grounding System

The KISS-SSB grounding system works on all frequencies from 2 MHz through to 30 MHz with an SWR of 1.2 or less and works just as good or better as the copper foil/bonding system.

It comprises of a 119 cms lead that attaches to the "grounding lug" on your tuner (ATU) and then you just stretch out the remaining 3 metres long tube inside the hull of the boat. It is that easy to install:
  1. No drag when sailing.
  2. No need to drill holes in the hull under the waterline for a "grounding plate"
  3. No need to run the copper foil everywhere.
  4. No need to bond all the thru-hulls.
  5. Maintenance free.
  6. Can even be used when your boat is on the hard and not in the water.
  7. Helps save your expensive radio gear in the case of a lightning strike, as there is not a direct connection to water.

Keep the KISS-SSB system clear of other cables and electrical systems, as these can cause interference to the KISS-SSB system.
The KISS-SSB is only connected to the ATU and not to any other part of the SSB system or yacht's electrical system.




Click here to order your KISS-SSB grounding system

Keep it simple

Around the Internet you will find many ways of installing an SSB, what works on one boat may not work so well on another, the best advice is keep it simple (KISS)!

Click here to order marine HF antennas, grounding systems and accessories

Looking for marine HF (SSB) transceivers!
Icom marine SSB Radio
http://www.sailcom.co.uk/transceivers

Phone: 01489 565100
Overseas: 00 44 1489 565100
Email Address - click here!



The Antenna Tuner Unit (ATU)

ICOM AT141The ATU electronically changes the length of the antenna by matching the transceivers output to the random length of the antenna. This matching changes frequency to frequency and therefore before transmitting on a new frequencies the ATU needs to be adjusted.
This is usually done by selecting the transmit frequency on the SSB transceiver and then pressing the TUNE button.
Pressing the TUNE button on the transceiver sends a very low radio signal to the ATU.
The ATU samples the signal and electronically adjusts the ATU to match the atennna.
This is done by using relays to switch coils in and out of circuit until the microprocessor finds the best match.
This TUNE process takes just a few seconds and if successful the word TUNE or a light will be displayed on the transceiver.
The ATU should be located close to the antenna and grounding system as the antenna starts at the ATU.

MF/HF DSC Watch Antenna

Modern marine SSB transceiver like the Icom M801E or M802 have a second receiver monitoring for Digital Selective Calling (DSC) Distress, Urgency, Safety calls and DSC distress acknowledgments.
DSC watch receiver requires its own antenna and a passive whip antenna longer than 2 metres should be used.
An active antenna, which requires power, should not be used because if the power fails then no Distress, Urgency, Safety or DSC distress acknowledgments are received. Also an active antenna does not comply with SOLAS regulations.

A VHF antenna is not suitable as a HF DSC watch antenna.
Click here for MF/HF DSC Watch Antenna



Components of an MF/HF (SSB) installation

There are a number of components requires to get an MF/HF transceiver system working on a yacht and they are all available from the UK leading marine HF (SSB) radio specialist - SailCom Marine
MF/HF (SSB) transceiver:-
- ICOM M802
Antenna tuner unit (ATU)
- ICOM AT-141
Cables between transceiver and ATU:-
- Coax (RG-213) cable
- Screened 4 core control cable.
Grounding system:-
- Ground plate or KISS-SSB counterpoise.
Antenna:-
- Back-stay or 7 metre whip
- DSC watch antenna
- High voltage (GTO-15) cable to go between ATU and antenna

Click here to order your SSB system

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Overseas: 00 44 1489 565100
Email Address - click here!

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