Technical Topics > Equipment

Equipent: A SW antenna

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DavidB:

--- Quote from: Dxer92 on August 31, 2011, 1705 UTC ---Does anyone know any kind of SW antenna that will work for my SW radio. I have a Grundig S350DL (No SSB) I have been trying to receive Pirate broadcasts here in North America but still no luck. I hooked up a CB antenna (The Antron 99)  but I am not sure if a CB antenna will work for the SW bands. Can anyone recommend any SW antenna's i can buy or build to improve reception so I can receive these Pirate broadcasts.

--- End quote ---

Several things. First, unless you live in a rural area, your biggest issue will almost certainly be noise. And it may well be noise even if you do live in a rural area. So many modern electronic devices (computers, light dimmers, plasma TV's, etc.) spew vast amounts of RF into the shortwave spectrum. Second, most shortwave portables are designed to work with a short whip antenna. In other words, they amplify the signal coming in from the antenna -- a lot. So the expected result of simply connecting a longer antenna to a radio like the 305DL is that you'll just swamp the thing with lots of RF crud, and still end up hearing little but noise.

What you should first do is to go out into your back yard (or if you live in an apartment with a balcony, out onto the balcony) and try to get as far away from buildings and wires as you can. Then see how much better your reception gets when you operate the set on battery power. Note that you should probably put your hand on the back of the set to provide some sort of counterpoise for the antenna to capacitively couple with.

If you still hear nothing but the harsh buzz of RF crud, then unfortunately shortwave is probably going to mostly be a lost cause at your home. Outside antennas can help in certain situations, but they cannot work miracles. If there's more noise than signal flying through space in the vicinity of an antenna, even the most expensive antenna and radio combination isn't going to receive much (if anything).

If, on the other hand, things get better in the yard, then there is hope. Portable sets can be very useful for pinpointing the sources of RF interference. If you have control over these, then you can simply kill the power to them when you're interested in listening to shortwave. Or maybe you can find a spot in your house where the built-in antenna on the radio works OK. Or you can try John Doty's design of a random-wire antenna with a noise-shielded feed:
http://www.iw5edi.com/ham-radio/?low-noise-antenna-connection,45

But the first thing is to determine if it's even worth trying harder at all at your location. About 80% of the urban locations I've lived in have basically been lost causes. I've taken to doing most of my shortwave listening when camping in remote areas (something which I can recommend to anyone: it's amazing what you can hear once you get into a truly quiet location, RF wise).

Dxer92:
Right now iJust bought another portable for $40 works great by the way. It is a Realistic DX-390 has SSB. But problem is is that when I hook up any kind of external antenna to it. I just get RF interference big time. Like buzzing noises i guess i am overloading the receiver. I don't know if there is any possible say to fix this problem it would be great if i could get away from all of the noises in the radio.

DavidB:

--- Quote from: Dxer92 on September 05, 2011, 2234 UTC ---Right now iJust bought another portable for $40 works great by the way. It is a Realistic DX-390 has SSB. But problem is is that when I hook up any kind of external antenna to it. I just get RF interference big time. Like buzzing noises i guess i am overloading the receiver. I don't know if there is any possible say to fix this problem it would be great if i could get away from all of the noises in the radio.

--- End quote ---

You might be overloading it, or if you're just using a plain wire as a lead-in, you might be routing that wire near a noise source. Tune the set somewhere where the noise is really strong, then disconnect the antenna and collapse the built-in antenna to its shortest length. Take the lead-in wire down, and use the radio to probe along the route of your lead-in wire to see if it passes by any noise sources. If so, either reroute or go with a shielded lead in like I mentioned in my earlier post in this thread.

As for antenna length and overloading, experiment with different lengths of random wire in an RF quiet location to determine if you're overloading the set with too big an antenna. It's definitely a possibility; portables are designed to operate with a short whip antenna and many are prone to overloading if you connect them to a long wire.

That said, if when you take the set out into your yard, the noise level drops appreciably, a short outdoor antenna with a shielded lead-in is likely to improve your listening experience over an equally short antenna indoors. If things don't appreciably get better when you operate the set away from the house, any messing about with external antennas will likely prove to be a wasted effort.

Nella F.:

--- Quote from: Dxer92 on September 05, 2011, 2234 UTC ---Right now iJust bought another portable for $40 works great by the way. It is a Realistic DX-390 has SSB. But problem is is that when I hook up any kind of external antenna to it. I just get RF interference big time. Like buzzing noises i guess i am overloading the receiver. I don't know if there is any possible say to fix this problem it would be great if i could get away from all of the noises in the radio.

--- End quote ---
Great radio. I bought mine shortly after "9-11". The local Radio Shack stocked way too many & eventually knocked the price in 1/2 just to get rid of the palitload takin' up all the floor space. Mine still works great. I've used both inside & outside antennas with no problems...once I found what was causing this, that, or the other rf. The radio seems to attract rf or maybe rf is attracted to the radio, don't know which. My plug-in rechargable Norelco rotary shaver wreaks lots of noise, as an example. Hope this is useful.

Pigmeat:
I had a DX-390 and they are prone to overload. 30 feet of wire worked well as an antenna for it.

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