Seting up a SSB ashore

30boat

30boat

N/A
Joined
26 Oct 2001
Messages
8,558
Location
Portugal
Visit site
When I had my Icom M710 on the boat I couldn't be sure it was emitting so I'm thinking of seting up an aerial and a ground plane and try it at home before I send it to the dealers.
What is the best arrangement?I was thinking of a simple wire aerial very much like the boat's backstay and for a ground plane an old metal water tank(full) .
Thanks.
 
Most developed countries have quite heavyweight regulation of who can transmit RF comms, using what, and from where - with quite heavyweight penalties for breaches of the relevant Regulations. Do satisfy yourself that you will not get an unwelcome visit from the Portuguese Radio Police....

/forums/images/graemlins/wink.gif
 
You may be able to use a copper rod driven into the ground as a grounding point. some houses already have them, so have a look round. The water tank will probably only work if it is grounded (I know nothing about plumbing so don't know if they are). Importantly, the connection between the radio and ground should be as short as possible. A simple wire antenna may work, but make sure it is correctly tuned to the frequency on which you are testing, either by using an antenna tuner or an SWR meter and trimming it to the correct length. You could try making up a halfwave dipole instead, which are good for simple tests, and this may be better suited for connection to your radio by using the coaxial connector. Alternatively you could try connecting a 50ohm dummy load and using another receiver near by, or connect a power meter to your radio, terminated with a 50 ohm load and check the output power. These are all general comments, i've no recent experience of SSB radios, but used to play around with them (HAM radio) many quite a few years ago. I'm sure someone will pop up soon with some more recently and relevant (marine) information.
 
You don't need to take the radio off the boat. Just buy a dummy load or a 100 watt power meter with a built in dummy load, you can then transmit with no fear of prosecution and can check the radios transmit output safely and easily into a matched load.
 
It may be worth getting a begginers book on radio electronics.

Both your SSB radio and the VHF radio are designed to be operated into an antenna with a specific electrical property, which is that it must have an impedance of 50 ohms. If you use the radio to transmit into an antenna other than 50 ohms, or if the antenna is unconnected, then you may damage the radio. A dummy load, sometimes called a 50 ohm load will do the job of an antenna (though a very inefficient one so you won't transmit far) and prevent damage to the transmitter, because you will transmit into a guaranteed 50 Ohms. In the UK they can be brought from electronic shops like maplin, and radio HAM shops. If you are doing any fault finding or adjustments to your radio then its generally considered good practice to operate it into a 50ohm load. Some people use a antenna switch so they can easily switch between the antenna and dummy load, or dummy load/power meter.

Its important to understand that the radio is design to be operated into a 50ohm antenna. The geometry of the antenna (length etc.) will change this value. So connecting any old bit of long wire to your radio and transmitting may damage it, as the impedance could be different from 50 ohms. If you are using the backstay as an antenna then there is probably a tuner between the radio and the backstay, this will make sure the radio 'see' a 50ohm antenna no matter what length the stay is. If there is no tuner then it may be because your radio is one built in. If it hasn't then get some advice about the installation.

I'd say its worth carrying a power/SWR meter, 50ohm dummy load and a spare antenna, which you can make from some coax and wire (a simple dipole). Have it already tuned for the SSB marine band in case you loose the backstay or or the antenna tuner packs up.
 
One of my beefs with the 710 is that the front panel 'power' annunciater doesn't show what's actually going out. Regardless of the findings, if you have that rig, you really should have a power meter in line to check things (similar purpose as an oil pressure gauge).

To measure, you need an in-line power/vswr wattmeter. They're self-powered (mostly),prices are modest, you can install it yourself, you just need an extra jumper of wire with a PL-259 on each end.

If, connected to your existing system, it shows no (or little) forward power AND reflected power, THEN borrow a dummy load (really a big 50 ohm resistor, it simulates a perfect antenna) and re-test.

Chances are high with the 710 that the problem is in the antenna system, not the rig. This would be indicated on the meter by a forward power of 12 watts or so (where the protection circuit cuts in), and a reflected power that pegs the needle.

Generally tho, a poor idea to move a marine band transmitter to shore and go key down without a lot of appropriate (and expensive) paper

Hope this helps,
 
I would Google a ham club in your area and ask them if they can help. Hams are helpfull people. There are many things which can go wrong with SSB, but hardly ever equipment breaks down. Just as an example: the antennatuner may not tune your backstay due to the length of the wire. Nothing wrong with this, just change the lenght. If its not tuned correctly, the transmitter may not transmit anything to protect itself. By the way, you will not see any outputpower on SSB if you just press the transmit buttom. You have to speak into the microphone to transmit.

Peter HB9TYM
 
Does it have an automatic aerial tuner? If so, it should indicate that it has tuned. That means it transmits - at least on low power. A subsequent radio conversation with a friend will confirm power and quality. Better to do all this on the boat as the whole installation will be tested.
 
I have a tuner and tuning is erratic.When I try to transmit the indicator on the panel shows nothing.The aerial is the backstay wich worked fine with the previous set I had ,a Icom M700.The set and tuner are connected to the iron keel with copper tape and the backstay is connected to the tuner by a thick copper wire.
Thanks for all the replies.
 
Lots of suggestions but if you know nothing about electronics, I reckon the best answer so far was to contact a local ham club. In the UK you can find one from the RSGB site on the www. If you make a crude home made aerial whilst knowing nothing about it, you might well fail and do some damage. Or you might make an aerial which is untuneable by your atu and prove nothing. On the other hand, any ham club is already likely to have a fully functioning aerial system plus power supplies etc, and likely someone who is an electronics whiz.

If your home base is anywhere near Bristol / Cardiff, bring it over to me and we can check it out on my home aerial system.
 
Thanks wotayottie,I'm based in Portugal so it's a bit too far.I think I'll send the set to the people who sold it to me and let them sort it out.I'll also give Chris Ridley a ring.
 
Dear 30boat,

Based on the number of 710s with the complaint of 'no power out' I've 'fixed' by curing a simple issue in the antenna circuit (in one case, not having the correct menu option set for his automatic tuner!), if you just yank the radio and send it to a shop, you may well get the radio back, along with a bill stating 'No problems found'.

One cruising yacht here (Fiji) went as far as to buy a spare radio. The issue? A loose DC connection to the tuner.

This is something which must be diagnosed on site (boat). Ask around locally, there must be either some hams or a local firm who has the gear to diagnose where the problem lies.
 
You must log in or register to reply here.

Share this page

Top