Reducing noise floor, fixable or just luck, Help/Advice

[osros]

Reviewed some posts but not finding what I need and this was difficult to find the right forum to post in since it covers alot, I figure you HAMs are the pros so here goes my situation.

I been SWL and Scanners off and on for a long time I enjoy HF alot and never had a proper antenna up due to some kind limitation. I will soon join in and be a Ham myself so now I m revisiting the issue of RFI/Noise floor and I want better. The issue: I have always been playing with a noise floor of about -80db to -90db in SWL I do my best and deal, I do okay but always had trouble getting those weaker ones in. I watch videos of others enjoying -100 to -120db and then again I see others where I am at more or less so I am unsure where I stand.

Is there really anything I can do to improve the noise floor for me?. Im not knowledgeable yet like most in radio so I can use some help I will continue my living situation,what I know and done so far.

Situation:
I live in north Texas near OK small town but decent size, old house and I mean old, old wiring, all is still two prong outlets. I have now a temp long wire outside my window to shack about 10ft up about 45' for HF. I had higher wideband & HF up at 25ft with no major difference. I am in process of ordering items & redoing all antennas and experimenting since I hope to also TX in a few months, but I am very limited in antenna location and config so trying to be creative.

What I know:
My house atm is not electrically grounded to the rod. Yeah I know I just felt you all slap your hands to your foreheads. I just discovered this and will have it shined up and new connector put on looks like the connector got old, corroded and broke off. Not sure if this will help my problem but needs to be fixed.

What I done:
In a effort to see if anything in the house is doing me harm I used a portable radio on AM on no station to see if I can get buzzing from areas of the house. I discovered a desk lamp which caused some RFI and its gone, LCD monitors in the shack some but cant change that. Router/Wifi but cant change that. They are causing some RFI but not effectng the noise floor that I can see. As far as I can tell I cant find much else with this method. I have RFI that I can see on my SDR displays that maybe external but we all get that on HF just not sure how bad it is for me.

Grounding plans:
On top of fixing the house ground to rod, I plan to have a electrician properly at least ground my shack in the house with true ground and 3 prong outlets as well and possibly a rod outside the shack and bring in ground thru the wall for a ground bar for equipment grounding.

Thats about it, not sure if I can improve things, it maybe just current conditions just dont have enough experience to tell.

Any help and advice appreciated.

 

[prcguy]

In most cases, grounding of your house AC mains or your radio equipment has no effect on noise pickup. In fact it can make it worse. I do a lot of portable operation from batteries with antennas hanging in trees near my house with no grounding whatsoever and its usually quieter than operating from my house with everything grounded way beyond what most people would do.

I suggest you map out some SWL or HF ham stuff with your existing radio and antenna. Then take the same radio and antenna or similar antenna at least 100ft out and away from the house powered by a battery. If your noise is reduced then stuff in your house or your internet lines or ?? is contributing to the problem.

If the noise is about the same operating portable away from the house then it could be noisy power lines in your area or something in the neighborhood that is radiating noise over a large area. There are various ways to see if the noise is coming from a particular direction and if so it may be possible to locate the source.

In the case of a noisy house you can install your antenna away from the house and use a pair of very effective common mode chokes, one right near the antenna and the other where the coax heads out of the house to the antenna. This will place the antenna in a quieter area and choke off RF noise induced onto the coax from stuff in the house that would normally run up the coax to the antenna and get picked up.

I've always had a mediocre common mode choke on my main multiband dipole at the junction of the ladder line and coax. I recently built two really effective broad band chokes replacing the one at my antenna and adding one at the radio where the coax heads outdoors. I saw an immediate reduction in my HF noise floor on the spectrum display on my radio and it was not subtle. The overall noise floor is now lower and most of the pips, bleeps and buzzes are greatly reduced or gone.

I have a lot of computer stuff at my operating position and some of my coax runs right across computer cables and wall wart switching power supplies. I suspect lots of noise was being picked up on the shield of my coax and was traveling up the coax and radiating into the antenna. Since I didn't really know there was a problem it came as a big and pleasant surprise when the new chokes killed some of it off.

So before you spend any money do some more tests and see if things are quieter away from the house. I can get you plans on making a very effective common mode choke, or just buy this one which is probably the most effective one made by anybody. CMC-130-3K - MyAntennas.com

This choke is not just some ferrite beads over coax like most, its got multiple large beads with multiple windings around each one and probably several different ferrite mixes to cover different parts of the band. This will fix a lot of noise problems but you have to make sure your noise is fixable first.

I see you are using an SDR dongle that connects to a computer, which can be a huge noise maker. If you have a more conventional SWL receiver try it on your same antenna in the house with the computer(s) shut off, then do the outside battery powered test. If your computer is the culprit and you take it outside powered from a battery it might just be moving the same problem to a different spot.

You might also check out the National Electrical Code, Article 810 on general grounding for antennas to answer questions on electrical safety and lightning protection, which is separate from fixing noise problems.
prcguy

Reviewed some posts but not finding what I need and this was difficult to find the right forum to post in since it covers alot, I figure you HAMs are the pros so here goes my situation.

I been SWL and Scanners off and on for a long time I enjoy HF alot and never had a proper antenna up due to some kind limitation. I will soon join in and be a Ham myself so now I m revisiting the issue of RFI/Noise floor and I want better. The issue: I have always been playing with a noise floor of about -80db to -90db in SWL I do my best and deal, I do okay but always had trouble getting those weaker ones in. I watch videos of others enjoying -100 to -120db and then again I see others where I am at more or less so I am unsure where I stand.

Is there really anything I can do to improve the noise floor for me?. Im not knowledgeable yet like most in radio so I can use some help I will continue my living situation,what I know and done so far.

Situation:
I live in north Texas near OK small town but decent size, old house and I mean old, old wiring, all is still two prong outlets. I have now a temp long wire outside my window to shack about 10ft up about 45' for HF. I had higher wideband & HF up at 25ft with no major difference. I am in process of ordering items & redoing all antennas and experimenting since I hope to also TX in a few months, but I am very limited in antenna location and config so trying to be creative.

What I know:
My house atm is not electrically grounded to the rod. Yeah I know I just felt you all slap your hands to your foreheads. I just discovered this and will have it shined up and new connector put on looks like the connector got old, corroded and broke off. Not sure if this will help my problem but needs to be fixed.

What I done:
In a effort to see if anything in the house is doing me harm I used a portable radio on AM on no station to see if I can get buzzing from areas of the house. I discovered a desk lamp which caused some RFI and its gone, LCD monitors in the shack some but cant change that. Router/Wifi but cant change that. They are causing some RFI but not effectng the noise floor that I can see. As far as I can tell I cant find much else with this method. I have RFI that I can see on my SDR displays that maybe external but we all get that on HF just not sure how bad it is for me.

Grounding plans:
On top of fixing the house ground to rod, I plan to have a electrician properly at least ground my shack in the house with true ground and 3 prong outlets as well and possibly a rod outside the shack and bring in ground thru the wall for a ground bar for equipment grounding.

Thats about it, not sure if I can improve things, it maybe just current conditions just dont have enough experience to tell.

Any help and advice appreciated.

 

[popnokick]

Another related article -
Grounding is key to good reception -- antenna special on hard-core-dx.com

 

[osros]

Thanks all,

I will see what I can do for tests and getting away from the house to see what the effect are. Im still testing around the house but I already basically cut power to almost everything and found it had no real effect to the noise floor. I can deal with some buzzing and other anomalies from other devices if I can get that overall noise floor down abit.

On the CMC-130-3K - MyAntennas.com that sounds like exactly what I need not outrageous in cost either. But in your description you have two, one at the antenna mast location and the other in the shack. Just wanted to make sure is two needed/recommended or can one do the job? Just asking, more is better I guess just want to be sure.

My main SDR for HF is the Elad FDM-S2 receiver which should be alot better than your average dongle and pleased with it, its in its own metal casing . I also use an Airspy (1st Gen) for VHF/UHF or my other scanners never really had a issue with VHF/UHF since my needs are local and RFI not as much of a problem for me there. More surprising is my AOR AR5000+3 receiver which is much worse with the noise almost all HF is S9 to +20 of noise floor on that radio either something is wrong or it is very sensitive. (This radio will be the one I go outside and test with). The FDM-S2 at -80 to -90 db is about S7-S8 which is not good but at least I can pick up better.

After all this reading I know I have some changes to make for safety and to help reduce noise I know in very basic way I have not taken some simple steps because I was just dealing with the noise instead of doing something about it. In the past when I did tie equipment together via antenna shields at the connectors even with simple alligator clipped wires I would have a noise reduction even when not sure if properly grounded, so I think i will do the grounding bar in the shack to a rod just outside.

I found RG8X going to my Hi-Pass filter and coming out to a RG58 about 2feet maybe not a big deal maybe it is but I like all to match and I need to buy and cut coax to the lengths I need and not get premade always leaving me with extra run not needed and used as is. Yeah BTW I have a AM station like 2-3 miles away so thats the reason for the filter, its does its job I can see the results on the display the station and that portion of the band is reduced alot but not really eliminated still a strong signal but overall no difference switched on or off on noise floor passed the AM broadcast bands.

I will attack these simple fixes asap perhaps will help, maybe not as much but I can then eliminate those possible causes.

 

[osros]

On the grounding, one thing Im not sure of and I maybe over thinking it.

Antenna/Mast, Coax, Lighting Arrestor, Ground rod....to....House electrical ground rod. That I got.

For purposes of noise reduction on the shack side I will have Radios to ground bar to 2nd ground rod right outside shack, do I also make a connect to House electrical ground or leave as is? I guess it will be connected in a way but like to know if I need to make a direct connect between rods?

House Rod---------Antenna Rod---------Shack Rod--------Radios


House Rod---------Antenna Rod----X---Shack Rod-------Radios
__________________|........................Coax....................|


Again noise is my concern. Excuse my simple understanding and layout.



Thanks

 

[cmdrwill]

Check this: Palomar Engineers® | Ham RFI Overview

Lots of GOOD information.

 

[prcguy]

You should always follow the NEC for safety grounding and they say any ground rod you add must be bonded to the AC mains ground and with at least #6 copper wire. In doing this you might increase the noise into your radio equipment and more often than not it does nothing to improve a noise problem.

Every house and situation is different and you won't know what affects the noise until you try everything. In an old house with two wire power distribution and no ground rod, the power lines to the house and in the house can act like a balanced transmission line and not radiate noise on the wires into the air very much. Introduce a third wire with multiple ground points and now the system is unbalanced and the wiring in your house might radiate more noise. This noise would be mostly from switching power supplies in just about everything already in your house.

Some antennas like the PAR End Fed have a grounding point and sometimes attaching that to a ground rod can reduce noise and improve reception and sometimes its worse. Partially because your coax is the other half of this type antenna and the coax could be carrying noise from stuff inside the house to the base of your antenna and grounding the PAR transformer might have a positive effect in that case.

Trying a battery operated radio away from your house will at least tell you if your area is potentially quieter or if your screwed. You might also take your battery operated radio to a local park or somewhere with no buildings or power lines. If you have the same noise there then you probably can't fix the problem. If its quiet at the park then try to find what part of your neighborhood starts to get noisy and you might find a guy growing pot in his basement and using high power grow lights which are known to produce a lot of RFI from their cheap Chinese power supplies.

I would not spend any money on a common mode choke until you know if your neighborhood is potentially quiet and you find your house is noisier than surrounding areas. In my case a really good choke at the antenna made a noticeable improvement over a cheap one I had been using and adding one near the radio made it a little better still. And I didn't think I had a noise problem until I saw how quite it is now.
prcguy

On the grounding, one thing Im not sure of and I maybe over thinking it.

Antenna/Mast, Coax, Lighting Arrestor, Ground rod....to....House electrical ground rod. That I got.

For purposes of noise reduction on the shack side I will have Radios to ground bar to 2nd ground rod right outside shack, do I also make a connect to House electrical ground or leave as is? I guess it will be connected in a way but like to know if I need to make a direct connect between rods?

House Rod---------Antenna Rod---------Shack Rod--------Radios


House Rod---------Antenna Rod----X---Shack Rod-------Radios
__________________|........................Coax....................|


Again noise is my concern. Excuse my simple understanding and layout.



Thanks

 

[prcguy]

Good reading but I don't buy any of their stuff. Palomars best common mode choke pales in comparison to the low end MyAntennas version.

I don't know the exact formula of the MyAntenns choke I copied but it looks similar to this: http://myantennas.com/wp/product/cmc-230-5k/

I used a pair of FT-240-31 cores wrapped with 12 turns of RG-142 Teflon coax then 8 turns around a pair of FT-240-61 cores inside the same box. It cost nearly as much to make as MyAntennas charges for theirs. The one I mentioned in an earlier post handles less power but is more effective across the 1.8-30MHz range.
prcguy

Check this: Palomar Engineers® | Ham RFI Overview

Lots of GOOD information.

 

[Comp-100]

On the grounding, one thing Im not sure of and I maybe over thinking it.

Antenna/Mast, Coax, Lighting Arrestor, Ground rod....to....House electrical ground rod. That I got.

For purposes of noise reduction on the shack side I will have Radios to ground bar to 2nd ground rod right outside shack, do I also make a connect to House electrical ground or leave as is? I guess it will be connected in a way but like to know if I need to make a direct connect between rods?

House Rod---------Antenna Rod---------Shack Rod--------Radios


House Rod---------Antenna Rod----X---Shack Rod-------Radios
__________________|........................Coax....................|


Again noise is my concern. Excuse my simple understanding and layout.



Thanks

Sounds like you might be asking for trouble by specifically creating an environment for ground loops. inside the shack you would need to connect the grounds I think.

 

[KC4RAF]

As 'prcguy' posted up in #7, follow the NEC

rules. Here's why; should lightning strike, (more than likely will never happen, but to be on the safe side), and damage your equipment, or burn your house down, and the insurance company finds that you DIDN'T follow NEC code, then there's a possibility they won't pay or reduce their payment to you.
But one thing for sure, you're still going to have a noisy floor, for that you have to do more research, as has been already mentioned.

 

[osros]

No problem I get the point made, NEC will be followed. Let me get some basic stuff done first before this gets overwhelming and frustrating before I even get started.

I guess will be shopping for a battery I assume a Marine battery deep cycle? Or suggestions?

Thanks

 

[prcguy]

My wifee headed up home claims for a large insurance company (20+ states) and she has never heard of a claim that was denied or even questioned due to grounding or lack of it.
prcguy

rules. Here's why; should lightning strike, (more than likely will never happen, but to be on the safe side), and damage your equipment, or burn your house down, and the insurance company finds that you DIDN'T follow NEC code, then there's a possibility they won't pay or reduce their payment to you.
But one thing for sure, you're still going to have a noisy floor, for that you have to do more research, as has been already mentioned.

 

[prcguy]

If you can connect your radio in a vehicle, take the vehicle to different places and check reception with the engine off. My goal would be to determine if the noise is wide spread or not without spending any money. Then if you determine the noise can be fixed, get the best solution for whatever your budget is.
prcguy

No problem I get the point made, NEC will be followed. Let me get some basic stuff done first before this gets overwhelming and frustrating before I even get started.

I guess will be shopping for a battery I assume a Marine battery deep cycle? Or suggestions?

Thanks

 

[k9rzz]

You got a video somewhere demonstrating your S7-8 noise floor? Even if just shot with a phone.

 

[osros]

You got a video somewhere demonstrating your S7-8 noise floor? Even if just shot with a phone.

Im sure I can give me a little bit and I'll whip it up.

 

[osros]

Heres a couple of vids.

https://youtu.be/N1_9vi8OodQ
https://youtu.be/gtfIaPqCAKE


The noise at 40m goes up or down across HF I can get -100 to - 110db in small areas like in 15 or 10m but not on video. Most is all as shown in video with slight changes.

The AR5000 the noise just kills this unit and stays at +20 to +40 you can even hear more than just normal static. There is little to no change anywhere I can get the meter to more match the FDM-S2 by applying Att 20db to the AR5000. This unit just seems alot more sensitive.

 

[prcguy]

Holy crap that's bad. What kind of antenna were you using? I don't see any typical noise humps or changes in the noise floor on the SDR. Can you change the vertical resolution to 5dB/div or less so its easier to spot where the noise might be higher or lower?

What your seeing is not normal and I suspect something in your neighborhood is making the noise. I have a portable HF loop with preamp that can find most sources of noise but your a little too far away to visit. The only thing that has been difficult to pin down with a directional loop that resembles your problem is power line zap on power poles. That is usually very broad band with minor changes in level from HF through VHF and sometimes higher.

Since that kind of noise radiates along the power lines its very hard to pinpoint, it seems to come from everywhere. I friend of mine has been successful in finding it by going around his neighborhood with a large sledge hammer and portable receiver whacking power poles and listening for a crackle or change in the noise. This method has found specific poles with arcing insulators but its also got him questioned by the cops.

I think operating portable in a different area will be very revealing and try to find an area not too far from your house but free of buildings and power poles. If you find that type of area is much quieter then you can migrate back towards your house and check for noise. If the noise picks up at some point see what is different like power lines, industrial buildings, commercial signs, etc.
prcguy

Edit: I believe some areas of Texas has BPL or broad band over power line Internet delivery. That can be really bad for HF reception but it should also have dead spots across the HF band.

Heres a couple of vids.

https://youtu.be/N1_9vi8OodQ
https://youtu.be/gtfIaPqCAKE


The noise at 40m goes up or down across HF I can get -100 to - 110db in small areas like in 15 or 10m but not on video. Most is all as shown in video with slight changes.

The AR5000 the noise just kills this unit and stays at +20 to +40 you can even hear more than just normal static. There is little to no change anywhere I can get the meter to more match the FDM-S2 by applying Att 20db to the AR5000. This unit just seems alot more sensitive.

 

[osros]

I got a feeling this is going to be a pain.

Heres another video this time a screen video hope I got the settings right.

https://youtu.be/DbbU-AYyDQE

Antenna is Par Electronics EF-SWL, not grounded atm.

 

[prcguy]

Looks like the noise is mostly in the lower part of the HF band. I see a peak around 5.7MHz and a slight dip around 8.8MHz then it really rolls off in the mid 12Mhz range. The peaks and nulls are probably where your antenna is resonant and not.

The most important thing I see is its very broad band but rolls off at some point where the power line zap I see around here doesn't roll off that low. Are there any businesses or industrial areas close by? How about a big house on the block with all the windows covered and nobody really comes and goes at normal times?

Have you checked it over a 24hr period so see if it changes or gets better late at night?
prcguy

I got a feeling this is going to be a pain.

Heres another video this time a screen video hope I got the settings right.

https://youtu.be/DbbU-AYyDQE

Antenna is Par Electronics EF-SWL, not grounded atm.

 

[osros]

Looks like the noise is mostly in the lower part of the HF band. I see a peak around 5.7MHz and a slight dip around 8.8MHz then it really rolls off in the mid 12Mhz range. The peaks and nulls are probably where your antenna is resonant and not.

The most important thing I see is its very broad band but rolls off at some point where the power line zap I see around here doesn't roll off that low. Are there any businesses or industrial areas close by? How about a big house on the block with all the windows covered and nobody really comes and goes at normal times?

Have you checked it over a 24hr period so see if it changes or gets better late at night?
prcguy

Im in south part of town mostly residential but there a gas station about half mile away maybe less, AM broadcast station 2 or 3 miles away Just alot of houses. I got no idea on the houses around here no big houses.

Its pretty consistent but I will take a fresh look at it and see if I see late night changes.