Safety Notice:

This advice for grounds and antennae is meant for HAM operators who have knowledge of the effects of RF voltages, and can take the necessary precautions to prevent any person from coming into contact with the antenna system during radio transmissions. If you must use the backstay or shroud as an antenna, then enclose the lower 10 feet in PVC tubing (you can buy lengths of split PVC tubing from marine stores) to prevent anyone directly coupling to the antenna. Then do the best you can to cover the backstay adjuster and lower turnbuckles. When I used the backstay for experiments on my boat I would not transmit unless I could see no-one close to the antenna system. For the primary radiator, many people use an insulated backstay together with a tuner which is there to fool the radio into thinking that you have a well designed antenna. If you had used a proper radiating element designed for the band you are using, you wouldn’t need to use a tuner. That’s what I now use.

The problems to be faced using a tuner:

It must be placed at the base of the antenna wire within six inches or so. This means an outside location somewhere above the push-pit and immediately below the lowest insulator. In power boats it is bolted to the house immediately below the whip antenna. This is why tuners are made waterproof, they are meant to be used outside the hull and cabin. The other requirement is that the tuner must be less than four feet above the water, so that the RF ground wire can drop straight to the sea via a fitting (metal) close to the surface of the water (a through hull, or wind vane paddle, or rudder shaft.) The wire must run vertically (slight bend is okay.) You can use wide copper strap which has a lower impedance to RF, as most of the RF current flows only on the surface of any conductor. I use 4 inch wide copper flashing as used on roofs, but not outside the boat where it will quickly corrode and become useless as a ground connection.


The purpose of the ANTENNA TUNER is to make sure that the transceiver can put out the strongest signal. The job of the antenna tuner is to MATCH the antenna system to the transceiver. Although it is possible to build an antenna system without using an antenna tuner, a "tunerless" system will only allow you to transmit on a limited number of the many frequencies available, unless you use a pre-tuned multi-band antenna, such as the Outbacker, or Moonraker .A long wire tunerless antenna system will not only hinder your ability to communicate on days when the propogation conditions are poor, but may also prevent your communicating with vital services such as the Coastguard, which frequencies are not within the HAM bands.

The cost of an antenna tuner is between $100 and $1200 depending on the level of automation that is built into the tuner. Some $100 manual tuners (you turn the knobs to match the system) do a better job at matching the antenna than some $1200 automatic tuners, it just takes a few minutes longer to manually "tune-up" before you can transmit. (Some automatic tuners will only work with an antenna that has an SWR of less than 2:1 - the marine antenna tuners often will only work with a specific vertical whip antenna - they can't handle a long wire at all. - a good manual tuner can handle about a 5:1 impedance range). The Yaesu tuner that I used on a GX757 could tune almost any wire I connected. (The Yaesu transceiver could also put out a signal into a 3:1 SWR antenna system - not so on the ICOM that choked when the SWR was over 2:1).

The reason for the short run of wire to the sea is that at the higher frequencies (20 Mhz and higher) any wire longer than 1/4 wave will seem to the radio as an open circuit (or high impedance) and will not connect the radio to its RF ground system. And this cuts down on the strength of the transmitted signal. Wavelength is calculated from 300/MHZ Meters. At 20Mhz this is 15 M, which makes a 1/4 wavelength only about 10 feet. Any wire that is 10 feet will not connect with the ocean, which is where most of the signal returns to the boat. Yes, strange isn’t it that the ocean captures the RF energy and brings it back to the radio. RF current from the radiator sprays out like a fountain into the sea where it flows through the water and back to the boat, eventually reaching the transceiver. The RF current is strongest closer to the radiator and gets weaker further away from the boat. Most of the RF current is contained within a circle of radius 20 feet around the radiator.

Importance of the Sea connection

It may help you to understand the importance of the ground system if you visualize the transmission line connections switched so that the center conductor is connected to the ground system and the shield is connected to the radiator. The transceiver would now send the electric current first into the ground system which becomes the radiator. The radiator would then become the collector which returns the electric current to the transceiver.

So, You can see that it is just as important for the ground system to act as a radiator as for the radiator to act as a collector. It probably would make more sense to call the ground system 'the collector/radiator', and the radiator 'the radiator/collector' but that's a bit cumbersome.

Just remember it is the hand over of electric current from the ground system to the radiator or vice versa that produces RF radio waves.

(In fact the transceiver constantly switches between the radiator and the ground system, sending electric current first through the one and then the other. The transceiver can't tell which is which).