I am currently crossing the Pacific (about 1000 nautical miles NE of the Marquesas) on a sailboat equipped with a short wave radio and I am trying to make it work.

The equipment is an ICOM IC-M710 with an automatic tunner AT-130 and a 3m long antenna. I have all the manual and specs.

When trying a lot of different channels, even in Puerto Vallarta on the Mexican coast, I could not get any signals. Only noise and interference, as if the radio was always badly tuned. I try to check stations schedule at the right time, and also communications from other sailboats who gave me their schedules and frequencies. Always nothing.

So my question would be: where to start to get this radio working ?

  • I do not have much knowledge about ham radio in general and short waves in particular
  • the equipment is 20 years old and I do not even know if it already worked. I try to check however all the boxes and the connections located in different parts of the boat and they seem ok (after a quick visual inspection)
  • am I even able to receive anything in my location? We just crossed the inter-tropical convergence zone and I heard it can mess with SW. Also, when checking the range of different stations on various website, I could find any that I should receive here for sure.
  • what is the range for this kind of radio ? The spec gives 150 W for Tx power below 25 Mhz and the antenna is 3m long. Any other factors impacting the range, maybe the frequency of the channel used ?
  • 1
    $\begingroup$ Apart from the good advice in the answers, what you really need is a few helpful people able to have a conversation, which this site is not ideal for. You really want a forum, perhaps Reddit amateur radio, or even a Facebook group, where you can work through everything step by step. It's probably one very bad connection, or configuration problem, but as you see below, it's almost impossible to write one offline set of instructions that cover every case, from your general description. An experienced ham or two will quickly home in on the problem and get it working as well as possible. $\endgroup$
    – tomnexus
    Commented May 5 at 17:20

3 Answers 3


This is the wrong time to be debugging a marine radio... Here are some things to check:

turn on radio, set to frequency (not channel) mode and tune to try and receive each of 2.5, 5.0, 10, 15, and 20 megahertz. If the radio is working you will receive station WWVH in Hawaii which is a beacon on precisely those frequencies that continuously broadcasts standard time signals 24 hours a day which sound like a series of beeps and clicks at 1-second intervals and every minute a station ID in human voice. Sometimes morse code is superimposed.

If you cannot receive WWVH on any of those frequencies, then there is something wrong with the radio or with the antenna. Proceed as per Kevin Reid's instructions.


I could not get any signals. Only noise and interference, as if the radio was always badly tuned.

I'm not particularly familiar with marine radio, but I expect it shouldn't be hard to receive something — if not necessarily what you want — most of the time when you are well away from land-based concentrations of noise sources.

In particular, you say that you cannot even receive

communications from other sailboats who gave me their schedules and frequencies

Assuming these other sailboats are within line-of-sight or close to it, you should be able to receive their transmissions easily (provided the radio is tuned correctly, of course). This strongly suggests that either your radio's receiver circuits, or your antenna, is broken.

Try disconnecting the antenna feed line (coax) connector from the back of the radio. This should cause a large drop in received signal strength (as seen on the front panel display, not by listening). If it does not, then either the radio is broken internally, or you likely have a break in the feed line somewhere between the radio and the antenna.

Disconnect and check every coax connector for corrosion or signs of water ingress — water getting into coax is very bad for it. Check other electrical connections making up the antenna. (It's okay to have rain and spray on an antenna, but the parts still need to make good electrical contact with each other where they should!) If it hasn't been checked for 20 years then something might be no longer weather-tight due to rotten insulation or gaskets.

Another possibility is that you have other electronic equipment on your boat which is radiating interference. Try temporarily shutting off power to all other equipment, and see if anything is intelligible then, and if the signal strength meter goes down (for less noise). If you find a culprit you can decide whether to try replacing it, shutting it off when you want to use your radio, or adding chokes for suppression of conducted noise to its wiring.

all the boxes and the connections located in different parts of the boat

All the boxes? Learn what all those boxes are. For example, if you have an antenna switch, perhaps it is switched to the wrong setting.

Consider eliminating complications and re-wiring.

what is the range for this kind of radio ? The spec gives 150 W for Tx power below 25 Mhz and the antenna is 3m long.

Receiving performance depends on:

  • how good your antenna is (appropriate length, pointed in the right direction),
  • how little noise is being emitted nearby (shutting off other equipment will help with this), and
  • your receiver's internal “noise floor”, determined by its design (this is rarely the problem except for receiving extremely weak signals such as from space).

The transmit power is completely irrelevant to receiving.

  • $\begingroup$ Thx Kevin, these 3 answers are helpful and I would have selected all of them if I could. For the Tx pwr, I know it is independent to Rx, it was just to have an idea for the other sailboats because there are not in line of sight, more like hundreds or a few thousand of NM ; all boats crossing from Puerto Vallarta to Marquesas is a small community but very widespread :) $\endgroup$
    – calandoa
    Commented May 5 at 20:21

There isn't a lot of activity on marine HF, but have you tried tuning into any of these nets, broadcasts, or beacons? https://www.yachtcom.co.uk/comms/frequencies/index.html Also, that radio has different modes, AM, Upper sideband and Lower Sideband, and digital modes for computer communications, are you sure you are in upper sideband (USB)? That radio should also be able to tune in shortwave broadcasts on 41M & 19M bands, and others. Here's a searchable list: https://www.short-wave.info/index.php

Some of the following is similar to Kevin Reid AG6YO post, but the testing method is different...

In the HF bands, any length of wire several feet long, that isn't grounded, should be sufficient for a receive antenna; so, for receive purposes only, I would try unscrewing the coax connector from the back of the radio and pulling out the connector so that only the inner pin of the connector makes contact with the radio's antenna jack inner pin receptacle. If your receiver's noise level, or indicated signal reception increases, you likely have one of these problems:

  1. Your coax shield and inner conductor are shorted together someplace. Disconnect the coax from both the radio and the ATU and use an Ohm meter to check continuity of both the shield and center conductor. If you can't get your meter leads to reach both ends of the coax cable, then first test the disconnected cable and make sure the center conductor and shield are not shorted together (you should see no continuity), then short one end of the coax, and make sure there is continuity (0 Ohms). If you get no continuity in both tests, or you get continuity in both test, you probably have a problem at one of your coax connectors.

  2. Your automatic antenna tuner (ATU) is bad somehow, and is not letting signals pass to the receiver. (ATUs use a series of relays to connect the proper combination of capacitors and inductors to match the impedance of the antenna, to the radio. Make sure you know the correct procedure for using the ATU, it might require you to transmit a low power AM signal to tune, before you switch to USB to listen.)

If your receiver doesn't get louder, or show a receive signal increase with the previous test, your receiver's front-end amplifying section might have gotten "blown-out" due to a high voltage (static on the antenna, or lightning nearby), and the receiver needs service.

My experience with radio in the salt water marine environment, is that connections corrode, and must be cleaned/repaired periodically. I've seen copper, especially the fine copper braid on the coax shield, turn to green dust.

There are a number of thing you could do if you have an SWR meter to test the antenna system, but I don't know what your capabilities are.

As a side note, proper grounding in the marine radio environment is crucial, because you are usually dealing with what is called a "compromise antenna", which is why you need an ATU, and if your ATU wasn't properly ground via bonding to some metal that makes contact with the water outside the boat, your antenna system is not going to be as efficient, and your path for high voltage static caused by wind going across your antenna, will be though your radios circuitry, which will blow-out diodes and transistors. ...ask me how I know.

  • $\begingroup$ Thx Louis, these 3 answers are really helpful and I would have selected all of them if I could. $\endgroup$
    – calandoa
    Commented May 5 at 20:22

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .