It can be very tempting to have CB, scanners and shortwave receivers all stacked up in a big impressive tower but some radio equipment doesn’t play nice with others sometimes causing a level of interference that makes at least one of them usable.

Having recently filled the shoebox that was my office/radio shack with all the equipment needed for my various radio hobbies it was time to find a bigger space. Even after setting up a mixture of desks and some very creative shelving it was starting to feel claustrophobic and I spent a great deal of time trying not to knock things over.

Part of this problem is a great love of vintage radio which generally needs a lot more space than the miniaturized modern radio kit now produced, along with the need for room to build electronic projects and layout all the tools that needs.

It was definitely time for some serious action!

The Lost Room

After taking the chance and offering our fast growing daughter a multitude of increasingly ridiculous brides to give up her larger room I admitted defeat knowing that the only option was to tackle the permafrost like pile of semi useless junk that has been gathering in the (surprisingly large) spare room or what we’ve come to know as “the room we do not speak of”.

For years the only contact with humans this room had was the brief moments when we would open the door and sling in the latest item that had fell foul of being outdated or just getting in the way.

Not really being hoarders but sometimes reluctant to throw things away this room has become the graveyard for everything from old toys, a television or two and a good quantity of the things that seemed such a good idea at the time they were bought only to reveal their pointlessness a few days later.

After a full day of painfully wrapping and moving everything to some newly erected outside storage it was time to unravel the nest of radios and wires built up over the last few years in my office.

Full Speed Ahead!

Seduced by all that space I got busy moving the mountain of radios and computers into their new home with total amnesia about the careful arrangement it took in the old room to have at least the main pieces going at the same time without badly interfering with each other.

JIL SX 200 Radio Scanner

JIL SX 200 Radio Scanner Tuned to VHF Airband

The worst culprit has to be a 40 year old JIL SX 200 scanner (pictured above) which not only leaves a very annoying regular clicking sound on almost every receiver nearby but is also useless if placed within 4 feet of even a vintage 200MHz computer due to interference.

Power supplies can also be a pain with it being important not to run the power cables too close to certain radios and it can take a long time to get a whole set of radios working together with everything else.

Varible CB radio power supplies

Home Brew and Manufactured Power Supplies

Having worked toward (and failed) zero cross interference for long enough with the old arrangement I have come to understand that not no matter how long I spend running power cables, antenna cables and placing the radios themselves there is never a perfect solution (especially with computers close by), accepting instead a level of interference that promises not to get in the way too much.

Interference from transmitters is going to be a lot harder to deal with but if your busy talking its not as if you want a multitude of others radios blaring at the same time. One unexpected side effect of moving rooms was when I discovered that a normal 4 Watt CB signal was making my brand new Internet router lose all connection to the web, giving me no option but to move it right to the back of the room.

Data Decoding and the Use of Vintage PC’s

Computers throw out so many stray signals across a wide section of the radio spectrum that they have been the number one problem for shortwave and scanner receivers. For radio contact logging and decoding data modes they are an important part of any diverse radio setup these days but by being a little creative you can cut back on this RF splatter.

Luckily most decode software will happily run on older less powerful computers that don’t throw out so much RF junk as something like a huge Pentium 4 running at a few gig. Computer screens can also be a huge source of RF and even if you have more than one computer it could be a wise decision to setup up a KVM switch so that they can all run off the one monitor.

Ive always found older laptops to be less of a interference problem than base units and can generally place these a lot closer to radio gear with very few problems.

Simple Ways to Track Down Sources of RF Interference

To save time and effort chasing your tail the first thing to do is check the “Birdie” frequencies for the radio your having interference problems with. Birdies are what seem like annoying interfering radio signals but are actually generated by the radios internal circuitry and without some sort of modification are unfortunately there for good.

If pulling the antenna out of a radio doesn’t make any difference to the signal level then you could be dealing with one of these unavoidable signal sources

Known birdies for a radio are often listed in the owners handbook or technical information supplied by the equipments maker. If you don’t have any documentation a quick search online for something along the lines of “radio make and model + known birdie frequencies” will nearly always give a result with the odds of finding a good list increasing the older your radio is.

Elimination Process

If your satisfied that the annoying signal getting in the way of your hobby is not being produced by the radio itself you can move on to finding the culprit. While listening to the problem signal start turning off the other radios and electrical equipment, starting with the big stuff like computers then working your way through everything else until the rouge signal hopefully disappears.

If you find the two pieces of equipment that don’t work well together you can sometimes solve the problem by increasing the distance between them and rerouting some of the power or antenna cables. Rearranging your shack to stop this interference is only practical to a point and unless you don’t mind walking around the room to use different things you may have to accept that they just aren’t going to play nice together unless they are in separate rooms (our houses).

The emissions from electronic devices has come under a lot more regulation in recent years with limits being set on how much broadband RF junk can be emitted but when dealing with the super sensitive receivers radio enthusiasts use this control often doesn’t go far enough.

When All Else Fails?

If switching off all your computer and radio kit hasn’t solved the problem it may be time to have a quick tour around the house and trying some of the big electrical items we use in our daily lives. Computers, old style tube televisions and plasma screens are well known sources of wide band interference and I would start with these.

Finding the problem outside of the shack my make you happy that you’ve nailed it down and its not your equipment being a pain but opens up a whole new set of (deeper) problems to deal with. Its fine if you live on your own but if not just try explaining to your partner/children that they cant surf the web or watch T.V while your playing with you radios 🙂

The Wider Problem with Interference

The sad truth is that any piece of electrical equipment has the potential to spew out huge amounts of RF energy across large sections of the radio spectrum and it doesn’t mean the problem is coming from within your 4 walls.

To anybody who has no interest or experience in the more specialized sides of radio like CB, shortwave etc the thought that the plasma T.V taking up the entire wall of the living room and requiring them to wear at least a basic level of sun block for more than an hours viewing could be ruining someones else’s free time isn’t even going to cross their mind.

So remember the problem could be something your neighbors using, a faulty power supply two houses away or some corporation piggy backing a data signal on the mains wiring and try not to drive yourself too insane narrowing down the problem.

Share on FacebookShare on Google+Tweet about this on TwitterPin on PinterestShare on StumbleUponShare on RedditShare on TumblrDigg this

Leave a Reply

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