100 to 500 KHz

[bearcatrp]

Have scanned this in the past. Very strong signals. Cannot listen to anything. Pegs the needle on a few frequencies like a dead key. Have tried every mode. Nothing. Could it be a local radio station? If so, thought I would be able to hear some kind of garble. Using a wire. Need a different antenna?

 

[icemantim8]

What radio(s) are you using to monitor that frequency range? Depending on what you are utilizing, it could be bleed over from the MW band.
That is a large swath of radio frequencies. Are there any specific frequencies within that range that you have captured.? For example, there are a lot of NDB's in that frequency range. For example in my area, Peterson Space Force Base is at 407 KHz. (Non Directional Beacons used for aircraft guidance and other uses.)

 

[jwt873]

The non directional beacons are between 200 kHz to about 520 kHz. They all broadcast their ID's in morse code. They can travel a fair distance. Especially at night. You should be able to hear quite a few between these frequencies.

I'm up in Manitoba and from Minnesota I've managed to pick up beacons from Warroad 360 kHz, Crookston 400 kHz and Fairmont 420 kHz.

Also, the 630 Meter amateur band is between 472 and 479 kHz.

What radio are you using.. Some are very prone to receiving interference from the Broadcast Band up above 550 kHz as a result of an inadequate front end and/or mixing stage.

 

[bearcatrp]

Used both R75 and R8500. The frequencies with a dead key and pegging my S needle like someone is next door has me wondering why I don't hear something besides silence.

 

[ka3jjz]

It wouldn't surprise me if the sigs that are pegging you are birdies or other mixing products. Circuit designs down here are really haphazard, simply because there isn't a lot of broadcasting on LW; it's slowly dying out where it does exist. There's absolutely none in the Americas. So there's little interest in putting good filtering, etc for this band.

A wire will pick up something, but unless it's REALLY long, it's horribly inefficient. There are designs for this band, but for most people, loops and active antennas are the way to go

Mike

 

[jwt873]

Like ka3jjz says.. It could be the products of mixing in the front end. I built a simple low pass filter to cut out a lot of the AM broadcast band hash to improve my listening below 500 kHz. How are you hearing these 'dead key' signals? Are there just two or three occurring between 100 to 500 kHz, or are there many? If there are many, are they evenly spaced or random?

Do you hear anything at all between 100 and 500? You should be able to hear at least one or two aircraft beacons sending modulated CW. There's a list of NDB's here https://www.dxinfocentre.com/ndb.htm Find one in MN that's near you and try tune it in.

If not products of mixing you could be hearing 'birdies'. If you listen to them using AM, they'll just be 'dead air'. But if you put the radio in CW or SSB mode, you'll hear a sharp note in your speaker that changes frequency as you tune across them.

Birdies are usually generated locally. Electronic equipment like routers, computers, video cameras, battery chargers, wall warts, and television sets are all capable of creating them.

Sometimes you can easily isolate the cause by turning off or unplugging devices like these and watching the radio to see if they go away. A more heavy handed approach involves shutting off circuit breakers in your house one at a time until the birdie goes away. Again, if the birdie goes away when you shut off one particular breaker, then you know which circuit the offending device is on and can narrow it down from there.

And.. I could be coming from outside. In which case tracking them down can be a lot harder.

 

[ka3jjz]

And to follow up - this doesn't mean the radios are defective - far from it. It's the circuit design (or sometimes the lack of) being used on LW lacks sufficient filtering and other processing to make it perform the same as HF.

Mike

 

[bearcatrp]

When I get time, will do a video and post it.