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Author Topic: Normal Noise or Troublesome Noise ?  (Read 7584 times)
KI7LFD
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Posts: 95




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« on: December 16, 2017, 08:56:31 AM »

As a new HF operator, with a new IC-7300 and a Myantenna 8010 End Fed antenna. I'm trying to evaluate my station that I just  assembled.  I've had the station running for a few weeks and I'm pleased so far.  But, I'm a newbie and very inexperienced. To get to the point, I don't know what an acceptable noise level should be or how to "measure it" ?  I seems to have a uniform level of noise on all bands, but know what to expect. I don't know how to "quantify" it.

I live in a very rural setting (think woods, deer, turkeys and moose)  .... with power lines about 1 1/2 miles away. I haven't witnessed any 60 cycle type interference to the best of my knowledge. My shack in located inside of a wooden enclosure that is itself located inside of a metal pole barn. The sheet metal of the pole barn is grounded as it the station itself (Ground rod). 

I just don't know what level of noise to expect in a good installation and how best to quantify it ?

Thanks in advance for the help.

Regards,

Rich (KI7LFD)

73
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AE5GT
Member

Posts: 396




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« Reply #1 on: December 16, 2017, 12:08:42 PM »

power line noise can sound similar to ignition noise. As a general rule , noise that is repetative is probably  man made  (listen to some of the recordings on Youtube) . Being 1 1/2 mile away i wouldnt think that you would have a significant problem with power lines ,however , unless you are "off grid " you will have a line to your house . 


Determining you noise is a bit tricky pass band width , receiver noise floor , preamp settings ,antenna type  will all affect the meter readings . 

If you miles away from any power consumers, then the most likely sources of noise will be self inflicted.  To determine if you have any issues , pull the main breaker/disconnect  at the power meter , and power the radio from a battery . Note the noise levels and radio settings . Turn the power back on , and recheck , there should be no difference .  If there is then you got issues that need to be dealt with.   

if you have a rotatable antenna and you notice more noise from one particular direction at all times then thats an indication of a problem.
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WB4SPT
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Posts: 777




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« Reply #2 on: December 16, 2017, 12:13:04 PM »

Measurement of noise, and getting calibrated "numbers", is rarely done by amateurs.   It would require a calibrated receiver, known cable losses, known antenna factors, and usually not really necessary.  

Pretty much is done informally using your built-in S meter.  Just a WAG here, but for 40 and 20 meters, an S0 pretty much means something is wrong with the antenna and/or receiver, and an S6 might mean that there is some unwelcome noise from a nearby source.   But, this is all rather guesswork at this point.  If you do hear quickly time variant noises, that might be on multiples of a frequency, that may indicate less than optimum surroundings.  You say "uniform level on all bands".   Of course, if there is no "useful" signal on a particular freq, then what you hear is 100% noise, correct?  
So, I guess, what CAN you hear?   There are some 24/7 nets, time standards, etc that you might report.  
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K0UA
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Posts: 4565




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« Reply #3 on: December 16, 2017, 02:55:55 PM »

Also a couple of "hints".  On your 7300, preamp 2 is not necessary for any use below 50 mhz.  AND even then it is usually not a good idea to turn it on.  Very rarely will it actually help, and will nearly always hurt.  You can use preamp1 on 50 mhz, and IF your local noise level is very low it MIGHT be helpful on 10 and 12, and perhaps 15 meters.  But not usually.  on the other HF bands, you will not ever want any preamp.  On the lower two bands, 160 and 80, much of the time you will want to use the attenuator, especially in summer static conditions.  You can try it without the attenuator and with and see which is better.  Remember always use the least amount of gain that will give you the best signal to noise ratio.  Now, all of that said what is your S meter reading on the various bands, at the different times of day without any pre-amps in and attenuation out.  I think preamp 2 is for up around 70Mhz. It is not useful for anything below that.   So report back on what you found.
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73  James K0UA
ARRL Missouri Technical Specialist
K8BYP
Member

Posts: 256




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« Reply #4 on: December 16, 2017, 07:41:13 PM »

Get rid of that Mickey Mouse antenna, from the website:

"Due to the High Impedance feed point, "

http://myantennas.com/wp/product/efhw-8010-2k/

A high impedance on the "other" end of the feedline turns it into a NOISE MAGNET.

That is essentially an open circuit at top with the feedline acting as a vertical antenna.

A new Ham in this area bought a G5RV for his first antenna and it was a total failure, he didnt have enough high points to hang it from to make it work, most
of the feedline was lying on the ground.

I've seen 'noise out of nowhere' solved by proper feedline tuning, especially on my 20M vertical, with all the feedline laying on the ground. Dipole, not so much.

Start with a good ol fashioned 1/2 wave dipole and go from there. Cheap and easy to make. Feed it with 75 ohm TV coax.

Avoid these compromise antennas.

"what level of noise to expect in a good installation"


Essentially none, or, if it exists, easy to locate to some nearby source like a noisy transformer on a power pole.

If its propagated noise, from a distance (implying the antenna is doing a relatively good job) then that noise varies widely with band conditions
and is generally low levels now with the horrible propagation we have now. Listen to 20M and up at night, they have been dead lately.

""I seems to have a uniform level of noise on all bands""

The noise is far from uniform on all bands. Most HF noise is lightning discharge, and the noise is maximum about 8 MHz.
Google terms like "distribution of noise in the HF spectrum" - Id once found a paper thru Google that showed a graph of this noise thru the HF bands.

If its uniform, then its not atmospheric noise, nor is it on one frequency.

The ground is terribly noisy, consider that's where the commercial power system is grounded!
« Last Edit: December 16, 2017, 07:53:10 PM by K8BYP » Logged
K5LXP
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Posts: 6136


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« Reply #5 on: December 17, 2017, 07:44:42 AM »

There's more than one kind of noise, so being able to discern which is which is the challenge.

Sometimes atmospheric or "band noise" can be quite strong with a good antenna.  In that case, a lot of noise isn't your problem, it just "is".  A poor antenna can make the band appear quiet, so low noise when it should be high can be in indicator of antenna issues.

Locally generated noise can happen any time for many reasons, so identifiying and curing the source of those can be a challenge.  "Band noise" will happen when propagation is open and usually accompanied by lots of stations on the air.  But interference will be there whether the band is open or not, and will have distinct characteristics like what bands it affects, how it sounds, and my vary in amplitude.   In my experience, interfering sources can sometimes sound like band noise but usually have some distinctive feature that tells me it's not.  Observing the noise over a period of time will reveal the characteristics like affected bands and time of day.

Not always, but most often any source of interference strong enough to be observed on higher HF bands is usually within your own home.  There is no end to the number of grunge-generating devices plugged into outlets these days, so going through the process of shutting down the house and isolating circuits can usually find most of them.

"Metropolitan QRN" is one reason I like to operate portable in the mountains.  It's so nice to have a good antenna high up in the trees, running the rig on a battery and hearing nothing but signals coming from the aether.

Mark K5LXP
Albuquerque, NM

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K0UA
Member

Posts: 4565




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« Reply #6 on: December 18, 2017, 08:02:27 PM »

If you could get a good look and a listen on youtube of your rf waterfall on the 7300 and also the audio waterfall on various bands, and various frequencies, we might be able to tell you more. 
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73  James K0UA
ARRL Missouri Technical Specialist
ZENKI
Member

Posts: 1636




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« Reply #7 on: December 25, 2017, 05:00:47 PM »

Read this link.

http://owenduffy.net/blog/?p=7879

Look at the ITU noise chart for your typical location.

I would use a good reference antenna like a half wave dipole even down low as a reference antenna for the noise levels.
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