Filtering out shortwave static

[dragon48]

I've "Googled" this up, but thought that the advice might be better here, knowing my location and setup:

NYC

AOR 8200 - stock BNC antenna and Stock MW bar antenna. FYI, the bar antenna appears to be useless, as with it alone, I can't even get local A.M. stations. I also bought this shortwave antenna - Amazon.com: Kaito T-1 Radio antenna: Electronics It is useless as well. I clipped it to to the top of the metal antenna and attached the other end to a high part of an outdoor railing. This didn't improve shortwave reception at all.

At night, I can get a lot of Shortwave stations coming in with strong signals, but except for a few, the static is so loud, that listening is either unbearable or impossible. In most situations, the squelch dial has to be at the utmost position for me to hear any voices and if I adjust it at all, I lose the voice.

To be clear, I hear the voices clearly and strongly, but the static is too much. I'm assuming that the static is a different frequency than the voices and there should be a good way to filter it out. Knowing my setup, is there some filter device that you can recommend to cut out the static? I had thought about picking up some sort of pre-amp, but am worried that it will also amplify the noise.

 

[ka3jjz]

No filtering needed, except the cerebral kind (hah)

The likelihood here is two fold - you've got something arcing in the area (neon lights, with the ballist failing, can do this...). The arcing would encompass a very wide range of frequencies.

The other is that there's a loose or bad connection in the 8200 somewhere, or there's a failure somewhere in the audio chain.

Mike

 

[jwt873]

If the noise is swamping the signal, as ka3jjz points out, your best bet would be to locate the source of the noise. Are you in a house, an apartment? To add to ka3jjz's list, plasma tv sets are horrible.. So are some wall warts and battery chargers.

Start unplugging things.. You can even walk around your place holding the radio near switches, breaker boxes and power outlets to see if you can pin down the noise.

For drastic measures, try turn off the main breaker so all the power is out in your house or apartment. See if that makes a difference.

 

[BushDoctor]

I've "Googled" this up, but thought that the advice might be better here, knowing my location and setup:

NYC

AOR 8200 - stock BNC antenna and Stock MW bar antenna. FYI, the bar antenna appears to be useless, as with it alone, I can't even get local A.M. stations. I also bought this shortwave antenna - Amazon.com: Kaito T-1 Radio antenna: Electronics It is useless as well. I clipped it to to the top of the metal antenna and attached the other end to a high part of an outdoor railing. This didn't improve shortwave reception at all.

At night, I can get a lot of Shortwave stations coming in with strong signals, but except for a few, the static is so loud, that listening is either unbearable or impossible. In most situations, the squelch dial has to be at the utmost position for me to hear any voices and if I adjust it at all, I lose the voice.

To be clear, I hear the voices clearly and strongly, but the static is too much. I'm assuming that the static is a different frequency than the voices and there should be a good way to filter it out. Knowing my setup, is there some filter device that you can recommend to cut out the static? I had thought about picking up some sort of pre-amp, but am worried that it will also amplify the noise.

Keep it away from TVs, try putting 2 ea 1N34 diodes across the speaker leads opposite polarity to each. other. A noise blanker is what you need when i turn off my blanker in a city I can't hear much on my ham radio in my car.

 

[dragon48]

If the noise is swamping the signal, as ka3jjz points out, your best bet would be to locate the source of the noise. Are you in a house, an apartment? To add to ka3jjz's list, plasma tv sets are horrible.. So are some wall warts and battery chargers.

Start unplugging things.. You can even walk around your place holding the radio near switches, breaker boxes and power outlets to see if you can pin down the noise.

For drastic measures, try turn off the main breaker so all the power is out in your house or apartment. See if that makes a difference.

I am in an apartment.

As a real test, I'll have to take the AOR outside, and walk over to the local river, which is the most distance I can get away from buildings without having to go too far. I'll do this at night, when I can get the best shortwave reception.

I did notice a few things:

The reception is the worst in my play room, which houses my PC (Chip is at 2.66 GHZ if matters) my Flat Panel TV, My Cable Box and Modem/Router, and my flat-panel PC monitor, which are always on. In fact, I can often get no reception at all, right in front of my PC and monitor. Currently, I am getting much better reception with the unit on top of my refrigerator, which is around 16 feet away - But there is still too much static. Not sure why, but if I go into the other room which is further away, the reception starts to get worse. This is even with nothing turned on in that room, so perhaps a neighbor has some device which is causing the interference.

Right now, it is cold and snowing, but as soon as it warms up, I'll test it outside. Assuming I get clear reception outside, I'll test interference by shutting things off one by one.

I did notice one more issue: Reception is much worse when I plug the unit into my external cube speaker, using a headphone to headphone jack - JAM Classic The speaker is charged so it isn't plugged in. Is is possible that the speaker is causing interference because when it is on, it is broadcasting its availability via Bluetooth, or is it jsut amplifying the noise?

I'll report the results of the various tests as soon as I perform them.

 

[slicerwizard]

I doubt that the shortwave antenna and the scanner have a good impedance match. Probably 300-600 ohm vs 50 ohm...

 

[sparklehorse]

Shortwave in the city can be tough. Really tough. Besides all the things in your apartment that can be noise makers, there's all your neighbors and the noisy things they own. But RFI noise can also come from things quite a distance away, including powerline insulators, and many, many other trouble makers. Check out this page from a Ham radio operator in the European countryside who has tracked many of his noise sources down over the years. I especially love the rain gutter story, but also the one about the brothel is a gem:

EMI - RFI page

.

 

[dragon48]

Shortwave in the city can be tough. Really tough. Besides all the things in your apartment that can be noise makers, there's all your neighbors and the noisy things they own. But RFI noise can also come from things quite a distance away, including powerline insulators, and many, many other trouble makers. Check out this page from a Ham radio operator in the European countryside who has tracked many of his noise sources down over the years. I especially love the rain gutter story, but also the one about the brothel is a gem:

EMI - RFI page

.

Edit - this exercise was done with the stock BNC antenna.

I'm actually quite surprised as to how well the AOR 8200 MK3 (I Haven't been fully describing the model in my earlier posts) picks up shortwave broadcasts in NYC! The problem is 100% related to my building and my apartment. As a test, I tuned to 6.020 MHZ (China Radio International) where indoors at night, I get a strong signal that is so distorted, I can barely understand the speaker. As soon as I left my apartment and entered the hallway, the audio got better. As soon as I was outside, the audio was near perfect, and when I walked a few minutes away, it was almost as clear as a decent local A.M. signal. I than manually scanned between 5.9 and 6.2 KHZ and was AMAZED at the number of clear stations that I picked up. It was as if I had a different radio. Inside my apartment, many of these frequencies showed up as strong signals, but the sound was 100% static.

I got a laugh at the quoted link's reference to a brothel sign interfering with signals and just experienced the exact same thing: While walking past a local "massage," place with flashing neon lights, my signal was interfered with so much that I couldn't hear anything until I was a few feet away.

I'm not confident that I'll ever solve my apartment reception problem, but at least I know that there is nothing wrong with my AOR. Maybe this will help push me out of the city into a nice house in the country!

 

[gmkelm]

For a test, I removed the wire from a wire reel SW antenna (Kaito, Sangean, etc.) attached the clip to my receivers whip antenna and let the bulk of the wire hang outside through a window. The improvement in reception was incredible. If you try this just remember to pull the wire inside when there is a threat of lightning. This is a real inexpensive and effective solution, particularly if you live on an upper floor.

Mark

 

[dmack550]

You might also try a power conditioner. Cleaning up the power can make a huge difference. They are available on Amazon and many other websites and electronic stores. I have one on my old Stratoworld receiver and it makes a big difference. I can't plug it into a regular outlet without getting all kinds of noise from my home's wiring and various appliances. Regular surge protectors just stop your equipment from frying but don't filter the power.

 

[dragon48]

I solved my problem with a low-tech method:

I bought 20 Gauge - 50 FT Copper wire. I wrapped one end to a railing outside my window and clipped the other end (with an alligator clip) to the end of the stock telescope antenna. I'm still working on the optimal place to leave the AOR in the apartment, but I can always buy more wire. For now, the difference is like night and day! I am getting nearly full strength signals and audio clear enough to listen to on some stations that I can barely make out if I remove the alligator clip.

I'm going to play around with different places on the railing to connect the wire to to see if I can get even better reception.

Can anybody suggest ways to modify my hack to get even better reception?

If I am stupid enough to have this in place during a storm and a lightning bolt hits the railing, will this destroy my radio permanently?

Thanks