Noise Levels

[Realtor MA]

A question for you ham operators;
What noise levels are typical on the various bands? I realize these things vary but as an example sometimes on 40 meters I'm looking at noise levels of s9 and I don't think it's ever been below s5 or so. As I go higher in frequency noise levels are lower and I'm not sure if that is a function of the sun spot cycle.

 

[Lucas McCain]

The noise levels you describe are essentially normal for around here but there are a number of variables such as the type of antenna and its proximity to noise sources. I have a full size 160 meter carolina windom and it routinely has a noise level on 20 meters of around S9. My 40 meter dipole on the other hand has much better noise performance and usually has a noise level on 20 meters of S0 to S1.

I have recently gone thorough my house and identified the noise sources and it turns out most of my local noise was created by numerous switching wall warts around my house. The cell phone charger, the laptop charger, the switching PS for my router... The list was long. The first thing you should do it try to identify the noise source, If you can run your rig off a battery, then turn off the main breaker in the house and see if it makes a difference. Then you can go circuit by circuit to identify the offending device. I have had to replace several switching supplies with linear types just to get things quiet. I now run the computer in the shack off an old astron linear supply.

If it turns out that the noise is not being generated by something in your house then try walking around the neighborhood with an AM radio and see if you can DF the source. sometimes it can be a bad insulator on a power pole or a leaky cable connection. If it is a source you can identify but not fix, sometimes you can null it out by changing the antenna orientation. If all else fails, you can try an RF phaser such as the MFJ-1026, these devices can in some cases subtract out the local noise electronically.

 

[Realtor MA]

Great info. Thanks. In general the noise level is higher on the longer bands and is only s1 or s2 on 10 meters. I'll try and play around a bit to see if there's any way of eliminating some of it.

 

[scouter-rick]

Lucas McCain raises some excellent suggestions. You can also get an idea of how much "atmospheric" noise you can expect by checking:

http://dx.qsl.net/propagation/

I also recommend making sure you have an excellent ground. I ran a seperate ground strap down through a solid copper conductor to a six foot ground rod that is dedicated to the shack.

 

[Realtor MA]

Lucas McCain raises some excellent suggestions. You can also get an idea of how much "atmospheric" noise you can expect by checking:

http://dx.qsl.net/propagation/

I also recommend making sure you have an excellent ground. I ran a seperate ground strap down through a solid copper conductor to a six foot ground rod that is dedicated to the shack.

Well, I think my ground is good. I'm sure it can be better. I have a strip of copper mounted on the back of the desk in my shack. Each piece of equipment is grounded directly to that ground bar with short runs of #10 stranded copper wire. Then I run a wire directly outside the shack and to a short ground rod(penetrates the soil about 2 feet). I probably should get another ground rod and drive it deeper into the earth. I wish there was a way of measuring the quality of a ground system.

 

[oneswithfunes]

s4-5 beaming Europe and rising to s7-9 as I turn toward Africa and south America. I have a power sub station south of me.

 

[Lucas McCain]

Any ground is better than nothing. You need a ground for a couple of reasons, one is for lightning / EMP protection. The second is the nebulous "RF" ground. A good RF ground can help you in a few ways but is primarily to provide a path for stray RF. Some folks say that you don't need an RF ground or they have never used one and never needed one and that may in fact be true. The truth of the matter is that if your antenna system is operating perfectly, then you probably don't need an RF ground, the issue is that most folks don't have a perfectly operating antenna system. I suspect that the ground system is not the source of your noise issue, most grounding issues show up on transmit. The first thing I would do is to make sure that something in your house is not causing your noise issue.

 

[Realtor MA]

Any ground is better than nothing. You need a ground for a couple of reasons, one is for lightning / EMP protection. The second is the nebulous "RF" ground. A good RF ground can help you in a few ways but is primarily to provide a path for stray RF. Some folks say that you don't need an RF ground or they have never used one and never needed one and that may in fact be true. The truth of the matter is that if your antenna system is operating perfectly, then you probably don't need an RF ground, the issue is that most folks don't have a perfectly operating antenna system. I suspect that the ground system is not the source of your noise issue, most grounding issues show up on transmit. The first thing I would do is to make sure that something in your house is not causing your noise issue.

Thanks guys I'm getting great info and advice.
So Lucas, I think you answered my main question but i want to be sure. You think that based on my previous posts my noise level is higher than it should be on the long bands?

 

[Lucas McCain]

There are many variables that can contribute to your apparent noise level, you have to determine what the various sources that contribute to the overall noise picture. Depending on your local circumstances, S9 on the lower end of the HF spectrum may indeed be normal. The only thing you can do is try to identify the most likely sources. For me, the biggest contributions to my local noise picture was the switching wall warts that come with every little widget you buy nowadays. The first thing I did was to turn off my main breaker and I immediately saw the noise drop way down. Now I knew it was something IN my house that was causing me grief. Then I turned it all on and with the radio turned up loud, I was able to go around my house and unplug the various suspects and hear the results. I found the biggest things that were radiating in my house were my router power supply, my laptop power supply and the video cable between my computer and my monitor. With those devices off, I was able to see a noticeable drop in the noise level.

So what I am saying is that all things being equal, it is normal to have a higher noise level the lower in frequency you go however what that actual level of noise is, is really dependent on a LOT of things that are not just atmospheric in nature. As far as your ground system, it wont make much of a difference with respect to receiver noise, it will most likely make a difference on TX.

 

[Realtor MA]

There are many variables that can contribute to your apparent noise level, you have to determine what the various sources that contribute to the overall noise picture. Depending on your local circumstances, S9 on the lower end of the HF spectrum may indeed be normal. The only thing you can do is try to identify the most likely sources. For me, the biggest contributions to my local noise picture was the switching wall warts that come with every little widget you buy nowadays. The first thing I did was to turn off my main breaker and I immediately saw the noise drop way down. Now I knew it was something IN my house that was causing me grief. Then I turned it all on and with the radio turned up loud, I was able to go around my house and unplug the various suspects and hear the results. I found the biggest things that were radiating in my house were my router power supply, my laptop power supply and the video cable between my computer and my monitor. With those devices off, I was able to see a noticeable drop in the noise level.

So what I am saying is that all things being equal, it is normal to have a higher noise level the lower in frequency you go however what that actual level of noise is, is really dependent on a LOT of things that are not just atmospheric in nature. As far as your ground system, it wont make much of a difference with respect to receiver noise, it will most likely make a difference on TX.

OK. This weekend I'll probably power the house down and see what happens. I'll let you know.

 

[cockpitbob]

Noise From Power Lines?

We finally bought a house and have moved. As soon as the level of cardboard boxes gets below shoulder-high I'm finally going to get into HF .

In my back yard are small power transmission lines. They are on 30' tall wooden poles, and the insulators only have 2 rings, but the lines are defenitely bigger than the normal street stuff distributing to homes. How likely am I to have noise problems from them?