Listener's Guide

Playing Safe With A Shortwave Radio

There is an awful lot going on in the world of wireless, many thousands of transmissions all seeking our attention, some weak, some very strong and all likely to interfere with each other.

By using an antenna that favours the frequencies we want to hear, it will go some way to discard those of less interest and reduce the chances of intermodulation products spoiling the fun.

Where Do All The Rejected Stations Go?

Down the GROUND wire into God's good earth. In many instances, this is via the earth lead in the mains cable and the plugs third pin. THIS LEAD IS FOR ELECTRICAL SAFETY AND SHOULD NEVER BE REMOVED.

The problem is this path is shared by every other electrical appliance in the house, some of which will be fitted with suppressors which will now be using the same path to earth electrical noise.

Nobody has ever taken the time to have a word with this interference, suggesting it should only go to earth without seeing your radios ground lead as a way into the set where it now finds itself in series with the aerial signal and so a part of it. Hence, more noise.

The answer is to add extra earthing as per the suggestions in the instruction manual. This will often shorten the earth path and make it more effective.

After a wet Saturday afternoon doing manic Dracula impressions with large earthing stakes, you may feel your attempts at getting a good earth are better than the bloke who wired your house and a strong desire to cut the earth lead in the plug. NEVER DO THIS. THERE IS A LEGAL REQUIREMENT FOR SAFETY EARTHING.

A Co-Axial Earth

Some have found using a piece of coax left over from the antenna installation as an earth lead has some advantages. The wire core and the outer braid are connected together at the earth spike outside.

In the radio room, only the inner core is connected to the GROUND point on the radio. As we have come to the sorry conclusion our earth lead is actually a part of our aerial, any interference picked up in the earth path is conducted to ground by the outer braid, leaving the centre core path in the clear.

If we have problems with mains-borne interference, one answer is to allow our signal earth and our safety earth to ground in separate paths. If we are to maintain the integrity of our safety earth we can build in a high impedance barrier at signal frequencies in this path and take our station earth to ground from the radio side.

This is nothing new. They were using isolating transformers as an end to common-mode noise back in the Thirties. These devices are now back in the accessory market. Forgive the wry smile of the old timer - the more things change to improve, the more they stay the same.

Shortwave Listening Safety Tips

If you are taking the traditional route to the hobby, the radio room or shack should be warm, dry and out of direct sunlight as the Manual advises. People also perform well under these conditions, the processors that operate a modern wireless objecting to cold and damp, just as much as we do.

A base station radio will usually mean an outside antenna, so site it where the downlead - a bit of wire or coax used to make the connection between set and aerial - is as short as possible. Not only will this keep the losses down, but that bit of wire is also acting as an antenna to any interference radiating from the house.

We now have many clever ways to get a clean signal to your radio via low-loss cables, phase-cancellation networks and matching baluns.

All receivers have the correct power connector for the destination country. If making any changes to power cables, seek qualified advice. When replacing the fuse in the plug, the UK standard 13 amp fuse will offer no protection.

A 2 amp fuse brings safety and peace of mind. If the radio is part of a transmitting station, pay special attention to the fuse values suggested in the Book of Words.

Radio manufacturers and engineers, especially this one, know what they are doing. This Guide upholds all that is written there on the subject of safety.

During the writers chequered career as an engineer with Lowe Electronics, he would stand back in amazement at the state of the plugs fitted to sets requiring servicing.

Loose cord grips, loose or badly oxidised fuses, loose pin screws and cracked casings lead to a rash of reported system crashes, violent intermittent interference and a range of it only does it once a month faults that caused the guys in Service to age three years for every one spent in a normal environment.

When we can get them out of therapy, they will lend a little reassurance that receivers and their Owners require the least attention compared to those who transmit. Our text today is It is better to receive than to send.