SSB installation

by Adrian on January 23, 2015

An SSB installation is not easy, and is probably the area of boat technology that is most susceptible to hard-to-diagnose performance issues caused by poor installation. There aren’t that many people out there with real SSB installation knowledge, especially on aluminium yachts, so I’ve read around, talked to lots of people and have tried to become an expert and understand the principles and recommendations of SSB installation, and most of my thoughts and understanding is here. At the end of the post I’ve uploaded additional resources I’ve found useful.

A typical SSB Installation:
SSB Diagram

The key areas to consider are:

    The Antenna
    The ATU
    Radio choice
    Installation and power
    DSC Usage
    Data over SSB

SSB is a fundamentally an old fashioned analogue technology, so It is worth taking the time to plan and do things right to ensure the system operates as well as possible. Poor quality wiring, water ingress or poor power will reduce efficiency, reliability and range.

The Antenna

There are 3 options for the SSB antenna.

1) Use a 7m whip antenna. This is probably the best antenna solution, but requires a sturdy two point mounting, whIch was a bit hard to fit in on our boat. A 7m antenna is also quite a beast and may get in the way of other things on a yacht.

2) Use a backstay as a long antenna wire. This is the most common option for sailing yachts, but had a couple of disadvantages for us. The backstay has to be removed, cut and re-joined twice at a specific points with electrical insulators. Whilst not a bad idea, ours had not been done when installing the rigging at the factory, so it was a reasonably large job that required outside riggers. On twin backstay boats like ours, I learnt that both backstays should be cut and insulated to remove the chance of signal interference between the two. The price for this work was nearly £800.

The backstay becomes electrically charged during SSB use, so the lower section that is in reach of the deck needs to be insulated carefully to remove the risk of someone touching it.

The cable connecting the Antenna Tuner Unit (ATU) and the backstay has to be installed carefully so that is is kept about 4” away from the backstay as it runs up to where the antenna segment starts. These stand-offs are quite often missed or done poorly by yard installations.

3 ) Use a plain old long wire. This is simple idea and works great for land-based installations. The issue is how to keep a long wire working and safe in a marine environment on the back of a boat. The best solution I have found is a concept used by They cleverly remove the core from the middle of an 8mm multi plait rope and replace it with a length of quality flexible insulated wire about 4mm in diameter. The wire is 17m long (I think) which is tuned to work best with SSB frequencies and it is inserted all the way inside the rope. The wire exit is fitted with a crimp terminal for easy connection via another short cable to the ATU.

Although it sounds easy, I decided to buy my rope antenna from in the US. It was around $200, so was worth just letting them make it properly. The owner is a chap named Dr John Gregory and he is a real radio geek. The actual rope is custom sized to match your yacht’s mast (mime was 52 feet long). It is spliced each end with an eye so the top end can be joined to a thin halyard line that passes through a block at the top of the mast and down again whilst the bottom end attaches somewhere at the stern to the top of the arch. The halyard is secured and tensioned so the Rope Antenna isn’t too tight but is away from all the rigging and backstays.

This was my initial installation diagram:
Rope Antenna Plan
(I actually ended up tying the halyard back on the arch to provide enough tension to keep it all reasonably taught)

The block at the top of the mast:
Rope Antenna Block

The rope antenna and cable exit connecting to the through deck cable:
Rope Antenna Bottom

The rope antenna is simple, does not require chopping up perfectly good backstays and theres not much that can go wrong in installing it. I chose it also because in the event of a mast failure, the Rope Antenna could still be hauled up whatever is left to hopefully still function as a perfectly good SSB antenna. It works very well and I’ve had no issues with it over the last year or so.

The antenna (whichever type is chosen) is connected through the deck to the ATU by another length of quality cable. I bought 2m of covered 1/4″ flex braid from RopeAntenna at the same time, as he seemed to think this was the best type to use. The length should be as short as possible to reduce RF loss.

To be doubly sure that no moisture gets in or damage occurs to this cable I encased in in adhesive heat shrink tubing. this ensures that the connections are solid and won’t move and there are no points open to the atmosphere anywhere in the cable run until it is below decks.

The through deck gland:
The through deck gland


Icom AT-141 ATUThe Antenna Tuner Unit (ATU) is a large box of electronic tricks that is usually mounted below decks underneath and as close as possible to where the antenna cable goes through the deck. The ATU is controlled by the SSB radio and by cleverly connecting different coils inside the box electronically varies the length of the antenna wire the radio signal has to pass through according to the frequency being used.

Lower (longer wavelength) frequencies (12 or 16m bands) need a long antenna (length of wire), so the ATU effectively makes the antenna longer. Higher (shorter wavelength) frequencies (2m or 4m) require a shorter antenna, so the ATU reduces the antenna length.

The ATU allows modern SSB radios to easily use different frequencies without the operator having to physically jump up, go outside and change the antenna length to match the frequency being used (as they did in the good old days).

I installed my ATU in the port transom area mounted to an aluminium bulkhead where it is free from movement or moisture.

In this photo you can see the small braided cable connected to the top terminal. This cable is also covered in clear adhesive heatshrink sleeve which starts above the deck gland and continues down to the terminal. This provides insulation and waterproofing.

Icom ATU

The antenna wire connects to the terminal at the top of the ATU and the terminal at the bottom needs to be connected to earth.

Herein lies another whole can of worms that can make the difference between a poor or good SSB installation…

Grounding – the earth connection

Typically on plastic boats an earth connection is provided by grounding the ATU to a copper plate fixed underneath the hull (as per Icom’s diagram above) so it is always in the sea. The obvious issue here is that that the copper plate needs to be fixed to the bottom of the boat and holes need to be made through the hull for fixing brackets so it is not a small job.

On an aluminium (or other metal) boats the hull is always connected to the sea, so technically the earth can simply connect to the hull.

However, connecting anything to the hull of an aluminium boat is generally bad news as it has the potential to allow galvanic corrosion to occur due to stray current leakage between one part and another. Aluminium boat owners NEVER connect anything directly to the hull or use the hull for earthing or as a common earth. Fortunately, connecting the earth strap to the hull via an RF blocking capacitor removes the potential for stray Radio Frequency (RF) and galvanic currents and mitigates this issue.

The earth strap should be a short length of good quality thick flat metal braid, and not just a wire. I used two short lengths to connect to the aluminium hull. One attached to the ATU grounding terminal and the circuit board with the RF blocking capacitor and the other from the other side of the capacitor to the hull.

Grounding from the ATU

All these bare metal braids and circuitboards are ripe for corrosion in the transom where I installed mine, so I’ve used spray insulator paint to coat all parts with an insulating varnish.

As well as earthing, you should ideally install a counterpoise or “radials”. These are two insulated wires (of a specific length) laid out in the bilges along the hull below the waterline, which although they doesn’t physically earth to the water, helps in some very weird and technical way to improve the RF signal.

Grounding.pngRopeAntenna supplied me a marine counterpoise which is two long lengths (10m+) of plastic insulated twin lead wire that is simply laid out through the hull from the ATU forwards. One length goes down through the starboard side bilges, the other through the port side bilges. They connect to the earth terminal on the ATU.

All this is before the actual SSB radio installation…

Radio choice

Icon are the premier supplier of marine SSB radios. They have (or had) two top end marine ready models, an IC-801E and an IC-802. Both are functionally similar, except the 801 is fully designed and certified for use in a marine environment with waterproof casings and (importantly for us aluminium boat owners) it isolates the DC negative from the antenna ground. Without this, when the SSB is on, the DC negative is effectively being connected to the boat’s hull, potentially allowing galvanic action and ultimately corrosion.

The 801E is (was) twice as expensive as the 802 for the same functionality to pay for the marinisation and European conformity. The 802 could not be sold in Europe as it had not passed the EU regulations, so generally people bought the cheaper 802 via US suppliers and eBay.

Icom 801

When we bought our 801 in 2013 the rumour was that Icom were stopping making them because of high costs and lack of demand. This may or may not have occurred, but they are currently in short supply. Whilst this doesn’t affect most people, the 801 is the only electrically safe option for aluminium and metal boat owners.

Installation and power

SSB radios are big and chunky with a huge amount of electronics. In days gone by a long range radio typically used by the military fitted into a lorry, so Icom’s current level of miniaturisation is amazing for old fashioned analogue (i.e. not digital) electronics. The radio comes in two parts, a head unit, which is the bit with the controls that fits by the chart table and the control box, which is about 50cm x 30cm x 15cm with a heavy chunky metal case.

We mounted our control box inside the chart table seat cupboard:
Icom 801 Control Box

The control unit is big but it contains some very clever electronics. For instance, the oscilating crystal (which is the core of any radio system) has to be so finely calibrated that inside the radio’s control box it is enclosed inside a special heater that keeps it at a precise temperature so exact and consistent frequencies can be obtained.

The SSB also requires up to 30Amps and 12V, so special (thick) cables are usually required running directly from the batteries. Since switching such high amperages needs decent contactors and the standard circuit breakers on the instrument panel are not up to the job I installed a 30A DPDT power relay so a small switch on my switch panel operates the relay which in turn activates the SSB power supply.

When buying the SSB I opted for the old fashioned bakelite telephone handset for speaking into instead of the handheld microphone. SSB signals are stronger the louder you talk, so the shape and design of the telephone type handset forces you to hold it close to your mouth thus it picks up more noise. It looks a bit like a WW2 submarine, but does the job. I also have an external speaker on the panel for just listening.

DSC Usage

A full modern SSB installation also allows Digital Selective Calling over SSB frequencies. This allows ships to communicate between eachother directly via digital messages. DSC is widely used for emergency alerting, and the DSC button on Icom’s radios can issue a distress signal that most large commercial ships will pick up at very long distances (as opposed to the 25 mile range of VHF DSC distress signals).

The DSC features need a separate 2 1/2 metre DSC whip antenna and an NMEA GPS feed to provide accurate location information. The DSC antenna screws into a standard 1” marine screw thread, so a mount or spare male tread is needed somewhere.

GPS information needs to come from a GPS antenna that is always on, such as the chart plotter or auto helm. An NMEA multiplexor or separate GPS antenna with a basic NMEA feed may be needed here.

I made sure we had spare mounts on the antenna tree I had made up with the arch solar panel installation.

I’ve also recently installed a completely standalone GPS antenna that is always on for supplying NMEA GPS data to the SSB and the VHF. This is a redundant system so the emergency functions of the radios still work in case the plotter dies. It uses very little power and was about £100 from Digital Yacht.

The antenna tree:


Data over SSB

Data via SSB is like stepping back 30 years. Data transmission is audible – a bit like a fax machine noise – thus is very slow (2400 bytes per second). To use the SSB for data communications a modem is required. This is an extra bit of kit that connects directly to the Icom radio, and to your laptop or computer via bluetooth. There is no c competition in this market, so the Pactor 4 DR-7400 is the best and model available, and I’d recommend the bluetooth version.

The only software that connects SSB radios to Pactor modems is free software called Airmail.


Airmail has been around for ages and was written for Windows 95. It is the only way to receive emails and data via SSB, so a PC or PC emulator is mandatory. The interface is old fashioned, and although it has been maintained, it has not been updated significantly for a very long time.

I bought a small dedicated Dell Venue 8” tablet computer to run Airmail on. It is small, it uses very little power and it can double as a spare chart plotter and navigation computer if necessary. It is mounted by the chart table next to the SSB and is a far better solution than a clunky laptop.

SSB and Tablet Install

Airmail provides very basic data features such as the ability to send and receive email ($200 pa Sailmail email account subscription required), the ability to listen to and convert weatherfax transmissions into weatherfax images and the ability to tune into and decode and display Navtext and other GMDSS information broadcasts. There is no web browsing, no apps, Facebook, twitter or other internet services, and it is all at a horrendously slow 2400k.

Although the data speed is slow, it is actually the same as basic satellite services (unless you pay $500+ per month and $10 per mb for a broadband satellite connection).

By way of illustration, the text on this page would take about 30 seconds to download. The whole page including images and graphics should take about a day – hence no web browsing!

This screenshot shows a typical Airmail screen showing the connection dialog connecting to a radio base station to retrieve email and the radio propagation graph showing when is a good time to communicate with each station.

Airmail Screen

Airmail works and is reliable. It is strangely satisfying to know you’re receiving emails via just a low tech radio and can do so literally anywhere in the world (given you may have to wait a few hours for the right atmospheric conditions to allow your radio signal to be bounced around the ionosphere).


The SSB installation is not simple as it is a complex bit of kit. The antenna has to be right for your boat. The connection from the antenna to the ATU has to be correctly insulated. The ATU has to be mounted below deck in a usually awkward location. The grounding has to be carefully thought out and installed properly. The (optional) counterpoise has to be run awkwardly through the bilges. The SSB control box has to be mounted somewhere it fits. The electrical supply has to be sufficient and appropriately wired. The modem and data connections have to be connected and a PC has to be used to run the (Windows only) old fashioned Airmail email, weatherfax and communications software. A DSC antenna should be used if the system supports it and a GPS feed is required for emergency position notifications. A Long Range Radio Operator’s licence and training is needed to use it…

However, all this gives you a long range radio that allows you to communicate with local ships between 200 and 2000 miles away and ground stations and email relay points 10000 miles away. It allows you to talk to friends and sailors on the other side of the world for free, and allows you to listen to weather and cruising nets containing local information. It is old and clunky and is sometimes doesn’t work when you want due to solar activity and the weather, but it is free to use and allows you to broadcast instead of being solely a one-to-one medium. It is designed for the remotest places on the earth where conventional communications isn’t appropriate or available.

Net ControllerOn our Atlantic crossing I used the SSB to help run the radio net which communicated with SSB equipped ARC fleet vessels daily. I also used it occasionally to receive emails and weather updates, but to be honest I used the Iridium Go! sat device more though for daily synoptic image and GRIB downloads as it was available whenever I wanted it, was easier to use my me (and others) than the SSB, worked on the iPad, used less power and with the unlimited data plan was cost effective.

I expect the SSB to come into its own when we’re away from modern communications, mobile phones, wifi signals etc in the pacific and elsewhere when radio nets are more important for local information and getting in touch with people via SSB is more commonplace. It is also a very useful backup communications system in the event of problems.


RopeAntenna Invoice – Details of the kit I bought from

SSB guide by Icom – Much the same as I’ve detailed here but a bit more technical and colourful.

Intro to SSB – A comprehensive guide book by Gordon West

SSB Radio bands – A handy frequency guide by Icom

Icom IC-M801 Manual – Icom’s manual

Pactor P4 Modem Manual – Pactor’s manual for the P4 Modem

{ 8 comments… read them below or add one }

Ernie March 9, 2017 at 08:21

thank you very much for this info. I am just on installing my 802 and the pactor and “had” some questions re installation. Now all answered.
I’ll buy you a beer if I don’t sink before then ;-).

happy sailing



Rob March 9, 2016 at 16:25

After reading your post, I’m disinclined to install an SSB and go the Iridium Go route instead. I’ll be cruising from the U.S. east coast to the Bahamas and the VIs. What do you think?


Steve February 10, 2015 at 21:35

Adrian, Great post, But I’ve got some bad news i’m afraid, i bought the lovely Dr John Gregory’s rope antenna just over two years ago, unfortunately the copper braid inside the rope isn’t waterproofed, so very quickly the salt water eats into the copper and creates a layer of oxide over it, reducing its effectiveness by more 50%, mine complexity disintegrated after about 18 months! :-( very disappointing to say the least.

Ive now replaced mine with Stainless steel with a silver-plated copper sleeve, supper strong and PVC coated

Hope you’re both well.



Adrian February 12, 2015 at 15:26

Steve, thanks for the comments.

Thats disappointing about the copper wire – I’ve ordered a length of the superior wire you sourced and will check my rope antenna when it arrives. I’ll update the post also.


Martyn January 24, 2015 at 17:17

Adrian…..thanks a million, this is about as comprehensive as it gets….I am almost sorry I asked. Now can you please get on with some relaxing.


Adrian January 24, 2015 at 17:21

Ha, we’re sitting on the boat anchored off a lovely white beach in Barbuda catching up with a few things. We have decent free wifi – this is about as relaxing as it gets. We went for a run earlier and will have sundowners later at five. All is good.


Mark Moss January 24, 2015 at 17:08

That was very interesting. Reminded me of the HF320 used in the Army. Had to work out what frequency to use and roll out the required length of antenna. Awsome though, used it lot in Jungle. Had a little hand generator that someone would wind like in a black n white war film!


Paul January 24, 2015 at 15:25

wow. very thorough post. thanks for the info! …..but i think you forgot the flux capacitor! ;-)


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