Get Currents In Your Inbox!

The Official Magazine of the Bluewater Cruising Association
SharePrintPDF

Water And Ground – Are They The Same?

Barb Peck & Bjarne Hansen

Hoku Pa'a
Niagara 35
August 3rd, 2016

Many cruisers choose to install a ham or marine SSB radio aboard, to chat on the nets and exchange email while at sea. If this is you, then you are probably interested in getting the clearest signal, the most range, and the least interference with other onboard electronics. A key component of a radio system is its antenna, and there are several things you can do that will improve its performance. Increasing the height of your mast is one, but let’s skip that and look at some easier options.

Most folks don’t realize it, but the wire poking up in the air (often the backstay) referred to as the antenna, is really only the top half of the antenna system.  A transmitting radio creates an alternating electric current between the backstay and ‘something else’.  That something else is whatever is attached to the tuner’s ground, and it forms the bottom half of the antenna system. So when you transmit, your radio causes current to flow in your backstay while an opposite current flows in the ground. This also explains why having a deficient radio ground can cause sporadic malfunctions of instruments, autopilots and other electronics.  The antenna’s electric field is set up between the backstay and the closest least-resistance ground, which may be your autopilot’s ground – causing currents to flow in the autopilot.  Improving your radio system ground will reduce these stray currents and should reduce the severity of the interference.

Cheap, Easy and Perfect?

There are several ways to provide that ground connection for the radio and, as with everything on a boat, none are Cheap, Easy, and Perfect at the same time.

In the category of Easy, there is the KISS-SSB Counterpoise (approx $200 from http://www.kiss-ssb.com/). It is a coil of bundled wires of varying lengths, which you unroll into your bilge or other out-of-the-way place. The idea is to have at least one wire in the bundle be a resonant length for the frequency you are using, such that the ground current flows in that wire.  Their web site states the KISS-SSB does “the same thing ham operators have been doing for nearly a century.“  While true, one should realize that this is what hams resort to when they don’t have access to a perfect ground. Counterpoises are necessary when your antenna is sited over dry, poorly-conducting soil that has high resistance to ground currents. Boats, however, float in an almost ideal ground (oceans of conductive seawater) – you just need to connect to it.

Which brings up a second way of providing a radio ground:  a steel or aluminum hull.  This probably qualifies as Perfect, but may not be Cheap nor Easy for everyone.

If you have a plastic or timber boat, then the traditional recommendation has been to line a significant portion (100 square feet is frequently mentioned) of the inside hull with copper foil and attach that to your tuner’s ground connection.  This provides a counterpoise like the KISS-SSB (imagine the copper foil as being a huge number of wires of many lengths, all spread out) and can work well, but is dauntingly difficult unless done at the time the boat is built.

How about a direct wire connection to the sea? Bronze through-hulls and rudder posts can work very well: read for instance the test results (link below) reported by well-respected ham and sailor, Gordon West, when he compares four different ground choices on the same 40 foot sailboat.  One of his conclusions: “If you are installing your own marine SSB or Ham radio system and are looking for an easy way to ground it, start by grounding to a convenient underwater bronze through-hull near where the tuner is mounted in the lazarette.”

If you don’t have a conveniently located piece of underwater metal, you can buy and install one such as the Dynaplate.  West Marine sells three sizes, ranging from 6” x 2” ($73) to 18” x 6” ($470) and though the manufacturer recommends the biggest size for Ham/marine SSB use, note that Gordon West’s testing suggests that the smallest size (which is similar in size to a through-hull) should perform fine.

Our Installation

On Hoku Pa’a we didn’t have any submerged bronze through-hulls near the antenna tuner, so we decided to install a metal plate. For $68 at Metal Supermarket, we got a 36” x 6” sheet of 0.050” thick copper.  This thickness needs tin-snips to cut, and should last decades in the water.  From Fastenal, $15 got us three bronze bolts, nuts and washers.  While hauled-out, we scraped bottom paint from a rectangular outline, shaped the plate to the hull with a mallet (this thickness of soft copper is quite manageable) and glued it on with 3M 5200.  Three bronze bolts located above the waterline provide a good electrical connection to a copper foil strip inside the hull, running up to the tuner.

StepsCollage

Radio performance has been great, and as one might expect, there hasn’t been any significant sea life growing on the copper plate.  It took less time to install than several square metres of foil would have, and was less expensive than a Dynaplate. My educated opinion is that it performs better than a KISS-SSB would in the same boat, but I haven’t had the opportunity to perform a direct comparison.  If you have one you are willing to move over to our boat for a few hours, we could try some tests similar to Gordon’s.  (Since I wrote this article, Hoku Pa’a has sailed to Mexico, so we would need to rendezvous down there!)

Of course, there are lots of additional radio system details hidden inside a boat. They can be covered in future articles if there’s interest.  Stay tuned.

Further Details

  • Gordon West (WB6NOA) operates a Ham radio school and has been Electronics Editor at SAIL magazine. His research report on boat radio grounding systems is a good read.
  • The Wikipedia entry for monopole antennas (which is what virtually every boat uses at HF frequencies) describes how the radiation pattern is formed between the antenna and ground.
  • I haven’t defined every term used in this article.  If on-line searches still leave you confused, drop me a line and I’ll try to point you in the right direction.

 

Comments


Leave A Comment

Your email address will not be published. Required fields are marked *

*
*


  1. Cameron McLean says:

    When we installed the ham radio on Mayknot there already was a zinc on the hull connected to the engine. We connected the radio ground to that and paralleled that to a few strips of copper in an easily accessible part of the bilge. Easy! Works fine – have contacted stations in Australia and Chile.

    1. Bjarne Hansen says:

      Hi Cam! Thanks for weighing in with a description of your installation and I’m happy to hear it’s worked well.

      There was a comment too from Jane G (but it is not showing up here on the website for some reason) about their KISS, which raised an additional point about that system. When the boat’s on the hard, a radio ground to seawater won’t work so well 🙂 In that case, I would expect the KISS system to be superior.

  2. Jane Goundrey says:

    We are in Guaymas too, on the hard- and installed a KISS just a year ago …. still trying to decide how well it’s working. I have emailed my husband your article as he is the electronics engineer on Salish Sequel…not sure how easy to lend it to you for a trial!

    1. Bjarne Hansen says:

      …I should have been more patient – your comment is now up!

      Yes, the logistics of meeting to coordinate a side-by-side comparison of grounding methods is challenging. But I am eager to try it sometime, as there are so many variables affecting radio performance (hills near the anchorage, what direction the boat is facing, nearby interferences, time of day, etc). The most reliable results would come from testing the grounding systems on a single boat, using an A/B/C switch to select between them while talking to another station.

      1. Jane Goundrey says:

        Talked to John this morning( he is away working). He says pretty easy to take KISS out of our boat and try in yours.
        We don’t return to Mexico until January though- where will you be then?

        1. Bjarne Hansen says:

          Our plans are still in flux, but it seems that Jan or Feb are most likely when we will get back to the boat…let’s stay in touch and perhaps we can get together then. Cheers, Bjarne & Barb

  3. Allen Dick says:

    Good article. An advanced ham since 1976, I have marveled at the radio grounding measures I have seen on sailboats and have learned to say nothing, even when the autopilot goes nuts whenever a mc is keyed. Every sailor seems convinced that copper in the bilge is necessary, even when sitting on the best ground plane one could ask for. I’ve also wondered why sailors don’t experiment with the various mobile ham antennas designed for cars. I’ve worked the world with a mobile whip.

  4. Brian Short says:

    Excellent article and a good idea.
    Thanks,
    Brian
    Carpe Ventus

  5. JG Nadeau says:

    I installed a copper plate below the mid ships waterline as a lightning ground in Gosling. I had to remove the sealife from it often, same as on the aft dynaplate. We had the 3″ copper ribbon strung out below the aft cabin bed and connected, thruhull, to the dynaplate and that worked quite well.
    Good article.
    J-G Nadeau
    Ex-Gosling, now Callisto
    VIctoria, BC

  6. Carl Nichols says:

    While I do agree with most of Bjarne’s comments, there are just a couple little blips that I would like to add. It was so nice to hear the part on how in the HF band of Marine SSB and long range Ham frequencies the antenna system is indeed a two part antenna, the radiating element antenna of choice (backstay, FG Whip, GAM, etc) the other half is actually called a counterpoise. The function of a counterpoise is to emit a low wattage 1 to 2 watts of counter phased signal. This counter phased signal is simply just that, the very opposite wave pattern as the high RF antenna, hence “Counter” phased. It is this low power counter phased signal that repels the high watt signal off of the radiating antenna and out into space. Because this counter phased signal needs to be below the main antenna it is called a “ground Plane”. A plane of counter phased energy below, or let’s say closer to the ground below the radiating antenna. Thus the name “ground plane” and not an “earth ground”. The use of radials as a counterpoise is still used with all AM broadcast stations below the main antenna.
    The biggest mistake that I see fellow cruisers doing is getting DC negative on the counterpoise by running copper foil to the engine, a shared bonze plate with the standing rigging, or tanks. If you get DC negative on your counterpoise then other electronics that also have DC negative will be potentially disturbed as they are also trying to emit this counter phased signal too. This is the main reason that auto pilots go hay wire when the SSB radio mic is keyed. I should also say at this time most all sailboats standing rigging is DC negative. Why you ask? The small VHF antenna on top of the mast mounting bracket is in contact with the shield of the coax coming from the VHF radio. The shield part of the VHF coax is DC negative.
    You have two choices for a proper counterpoise (ground plane), 50 plus feet of copper foil that does not get into contact with DC negative or the KISS-SSB. Connecting the copper foil to the water does not do anything, yep, read that statement again. It is the copper foil that is radiating the counter phased signal, 2 through 30mhz does not penetrate but a few inches of water and the water does not emit the counter phased signal at all. The water however is a great reflective surface to help our RF signal out into space. I have demonstrated this often, next time your in contact with someone 500 miles or more disconnect the foil from the bronze plate and the receiving contact will not see any difference with your signal strength. Many cruisers out there have just a few feet of copper foil going to a sea water connection via a rudder shaft, thru-hull valve or a bronze under water plate and think they are doing great making contact 500 to 1,000 miles away with good propagation, but, are they getting the 2,000 to 5,000 mile transmission? Probably not. It is the short piece of copper foil that is doing the job as a counter poise.
    DC negative on our vessels is a decent ground, the engine block is DC negative with a large shaft to a prop in the water. But, if you get DC negative on the ground/counterpoise lug of your tuner you probably will cause other electronics to go hay wire and you will limit your SSB RF signal strength out into space. Most everyone knows about the well publicized mistake in the Icom M802 manual about not using the green wire at the end of the radio to tuner control cable, the reason is that one end is connected to the chassis of the M802 (which of course is DC negative) and if you connect the other end like the manual says to the ground/counterpoise lug of the tuner you will lose nearly 45% of your signal strength and it is being absorbed by your DC negative system onboard. If you call the techs at Icom America they will say do not use that green wire at the tuner end of the control cable, simply tape it off. They have been trying to get that changed in the manual for over five years now. Every cruiser out there should have a copy of either Terry Spark’s “802 Starting From Scratch” or Capt. Marti Brown’s book “802 for Idy-Yachts” These books go into better detail about the green wire at each end of the control cable and the better choices for a proper counterpoise/ground plane.
    Okay, by now you have probably figured out that I am your neighbor here in the Bellingham, WA area that owns the patent on the KISS-SSB. I tried very hard to write this comment with out being biased and to explain the counter poise in it’s full detail. Back in 2007 I personally was on my own sailboat 3,000 miles away in the Marquesas talking with Gordon West in S. California and he was very pleasantly surprised of my signal strength using the backstay and the KISS-SSB counterpoise. He does send us customers often along with Icom Of America too. I am 60 years old now and have been an active ham radio operator since I was 14 years old, KE7FGF. Back a few years ago a group of cruisers in Mexico did a big test between the bronze plate and the KISS-SSB, take the time and read about it at our website in the testimonial section. Honestly, my main goal is that each and everyone of you cut the dock lines and go enjoy the cruising lifestyle along with one of the best SSB radio signals out there. Go out there and enjoy paradise at a level of peace that you may never feel while being land bound.

  7. Scott Crawshaw says:

    Hi Bjarne, thanks for the article and helping fellow cruisers to getting the ground plane for SSB right; it is critical to good transmission and reception. Onboard Peregrinata I chose the cheap but not so easy method of going to metal supermarket and buying a roll of two inch copper tape, disassembled the quarter berth, and glued the tape to the hull in a grid pattern. I also soldered the copper tape to itself at each junction. This was a lot of work, and likely falls in your category of dauntingly difficult, but I feel it was worth it. Not only did I gain a much better understanding of my own setup; we ended up with one of the strongest signals while we were cruising. I used to often chat with Don Anderson in S California throughout our S Pacific crossing and we heard each other loud and clear.
    I look forward to your next article, enjoy Mexico!!

  8. Mark Misian says:

    It would appear that they both work just fine. I went with the KISS-SSB eight years ago and it took me maybe 30 minutes to install. I was told that we had the best signal in the Puddle jump and the Baja HaHa back in 2008 we ended up doing relays for others. One of the net controllers was Gordon West. Now eight years later my fellow cruiser friends are having to change out their copper foil due to corrosion but the KISS, being a sealed unit is just like new and still works well. I had changed from copper foil that was on the boat to the KISS and saw a big difference in Sailmail connections and the baud rate nearly doubled. If you take simplicity of installation, cost and reliability without having to worry about corrosion issues I have to agree with Capt. Terry Sparks and will continue with the KISS-SSB for my ground plane.