I have a problem of RFI effecting my laptop

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#1
I now have a Dell Inspiron 3541 laptop OS Win 7 Home 32bit. It came with Win 8.1 installed. But I don't have a Win 8.1 install disk and I heard a few bad things about 8.1 so I installed my Win 7. I got the Dell laptop because I was having problems with the HP Compaq Presario C700 laptop that I had. The HP laptop it self was on it's last leg as it was without the RFI. I was having RFI in the shack bothering that laptop. Even my Baofang ht with a 2m/70cm magmount antenna outside on my window a/c unit bothered my HP laptop. I sometimes pickup radios from yard sales, fix them up and sell them. Even on a dummy load there is enough RFI in the room to make the old HP laptop go nuts. So I got this newer Dell laptop. The Dell laptop is not bothered by my cell phone, frs ht's, the Baofang ht and the wireless house phone like the HP laptop was.
But the USB plugins, like the 500gb Sata HDD in the external USB case and the Logitech wireless keyboard and mouse still go nuts when I tx on the Baofang ht. I need some help figuring this out because once I get my HF loop antennas built and the tuner mounted out on the balcony I want to do digital HF tx

Steve.
 

buddrousa

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#2
1. I would look at grounding all coax leads in the shack.
2. I would look at Type and Brand coax in the shack.
3. I would recheck all connectors on all coax in the shack.
You have a large RF leak in the shack from the sound of what you are saying.
 
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#3
Mag mount antennas are notorious for radiating RF from the coax. And having your antenna in the window is going to put a large amount of RF in the house even if the mag mount isn't radiating from the coax. Get a real antenna and put it on a pole or tower above the peak of your roof. You will always have problems with your current antenna setup.
 
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#4
I live in a 2nd story apt. The only ground source available is the water main pipe coming up from the ground and into my bedroom closet. Yes the hot water tank and the main and secondary water shutoff valves are in my bedroom closet. It was a German company (from Germany) general contractor that built these apt's. That's how they build them in Germany.

1. I would look at grounding all coax leads in the shack.
2. I would look at Type and Brand coax in the shack.
3. I would recheck all connectors on all coax in the shack.
You have a large RF leak in the shack from the sound of what you are saying.
 

ka3jjz

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#5
You have another issue, and that's the laptop itself. You should look at choking off all leads going to and from the laptop, as that too can act as an unintended antenna for RFI. While that will cut it down, the plastic case of the laptop is invisible to RF, so it likely won't be a cure all

Unfortunately that water pipe is virtually useless as an effective RF Ground. It's likely to wind itself around your complex (making it physically long) and unless it's well bonded at each joint, it's quite possible that it wouldn't be effective anyway. If you're sticking with 2m/70cm, you can build a better solution than that mag mount. Do some homework on the net on dual band antennas...here's just one example...and get it outside!

The NA4IT CHEAP Dual Band Ground Plane Antenna

Mike
 
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#6
I live in an apt. No antennas can be mounted anywhare on the outside of the building except for Dish network and Direct tv antennas. That's why I have the 2m/70cm magmount on the top of the window a/c unit. The swr's on 2m and 70cm antenna are just a hair under 1.5 to 1. I can have an antenna on my balcony on a tripod as long as the tripod is not bolted to the balcony. I have 3 cinder blocks, 1 on each foot of the tripod and the tripod is wired to each block. I am going to put my hf loop antenna on the tripod. Now since I got the newer Dell laptop to replace the old HP laptop. The receive on my Icom IC-730 hf rig is not getting wiped out by the laptop unlike what the old HP laptop was doing. The old HP laptop was just about ready to kick the bucket anyways. The old laptop was a HP Compaq Presario C700. I now have a Dell Inspiron 3541 and it came with a month and a half left to go on the manufacturer's warranty when I got the Dell laptop from the pawn shop. A real steal for $100. out the door

Mag mount antennas are notorious for radiating RF from the coax. And having your antenna in the window is going to put a large amount of RF in the house even if the mag mount isn't radiating from the coax. Get a real antenna and put it on a pole or tower above the peak of your roof. You will always have problems with your current antenna setup.
 
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#7
The 2m/70cm magmount antenna is on the outside part of the window a/c unit. There is no room on the inside part, also the inside part of the window a/c unit is all plastic.

You have another issue, and that's the laptop itself. You should look at choking off all leads going to and from the laptop, as that too can act as an unintended antenna for RFI. While that will cut it down, the plastic case of the laptop is invisible to RF, so it likely won't be a cure all

Unfortunately that water pipe is virtually useless as an effective RF Ground. It's likely to wind itself around your complex (making it physically long) and unless it's well bonded at each joint, it's quite possible that it wouldn't be effective anyway. If you're sticking with 2m/70cm, you can build a better solution than that mag mount. Do some homework on the net on dual band antennas...here's just one example...and get it outside!

The NA4IT CHEAP Dual Band Ground Plane Antenna

Mike
 

ka3jjz

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#8
At least the antenna shown won't have the possibility of the coax acting as a radiator, as mag mounts sometimes do...Mike
 
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#9
I've been in a room full of laptops (40 of them) with a ham h/t sitting literally ON each one while in an FLDIGI training class. No one has an RFI problem.

So laptops are not particularly sensitive to RFI, that's a wild goose chase.

Most likely the problem is related to RFI and grounding, and I'd suggest buying the overpriced ARRL books on both topics, so you get a more complete picture of all the issues relating to both. The answer could be a simple problem like the house wiring being improperly grounded, that's common enough.

You also don't say how you got this laptop but it sounds used. It SHOULD have come with a Microsoft "Certificate of Authority" or similar still glued onto the bottom of the computer. If it did not--you weren't entitled to the original operating system, the license was stripped off and someone else is using it. But if the certificate sticker is still there, CALL DELL. They can send/sell you a factory restore disk, or an OS restore disk. Sometimes they only sell the factory restore disk, and you can only make OS restore disks from the factory installation. Or, you can actually call a very little known Microsoft licensing division and they ca sell you replacement media. Which is exactly that--the media to reinstall the original OS, with no license. You'll need the COA sticker on your laptop to enter a valid installation code.
I strongly suggest this, even if you don't have Win8 or want it, because if that's what the computer shipped with, that's what the drivers were also matched to, and at some point when you want to need to restore the working OS? It may no longer be available. The disks (from Dell or MS) are often available for anywhere from $15 (MS) to $50 (some brands).

But check your premises wiring and your RF situation, your laptop should NOT be the problem, it is almost certainly just collateral damage.
 

ka3jjz

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#10
I would stress that while laptops may not all be sensitive to RF intrusion, the cables that go to and from a laptop most definitely can be. When chasing RFI issues, you really need to think in terms of 'what can radiate' and 'what can receive'. That's often what makes it such a bear to track down

Mike
 
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#11
I got the laptop from a pawn shop. I know that the laptop was under the manufacturer's warranty when I got the laptop. When I got the laptop the warranty still had a month and a half before it ran out. I know this because I had the motherboard replaced under warranty when the audio jack developed a cold solder joint (the audio jack is a single jack, both in and out). I could have fixed the cold solder joint my self but that would have violated the warranty and with my shaky hands due to miro hand tremors. That's why I had to retire 15 years ago. I was screwing up to many pc boards. When all the USB lines into the laptop are unplugged and turned off, like the hard drive in the external USB case. This Dell laptop has no RFI problems with the ht or the Icom IC-730. With the antenna setup that I have mounted on the tripod on the balcony right now I can safely tx on 10 meters. The old HP laptop I had (ruff guess was built in 2000) and had problems with RFI regardless if any of the USB stuff was turned on and plugged in.
Rred I live in an up stairs apt that was built in the late 1990s. So I can't do much about the house wiring. I 2 have been in a room filled with laptops with no RFI problems. The ham shack at the Red Cross building in Kennewick, Wa is proof. That room was wired from the ground up the right way. I just don't know how to solve my problem given the setup that I have to work with. Also all 3 of the Radio Shacks in town have dried up and gone away. So no local source for parts any more. The nearest parts store is Jameco Electronics in Seattle Wa. A 6 hour drive 1 way.

I've been in a room full of laptops (40 of them) with a ham h/t sitting literally ON each one while in an FLDIGI training class. No one has an RFI problem.

So laptops are not particularly sensitive to RFI, that's a wild goose chase.

Most likely the problem is related to RFI and grounding, and I'd suggest buying the overpriced ARRL books on both topics, so you get a more complete picture of all the issues relating to both. The answer could be a simple problem like the house wiring being improperly grounded, that's common enough.

You also don't say how you got this laptop but it sounds used. It SHOULD have come with a Microsoft "Certificate of Authority" or similar still glued onto the bottom of the computer. If it did not--you weren't entitled to the original operating system, the license was stripped off and someone else is using it. But if the certificate sticker is still there, CALL DELL. They can send/sell you a factory restore disk, or an OS restore disk. Sometimes they only sell the factory restore disk, and you can only make OS restore disks from the factory installation. Or, you can actually call a very little known Microsoft licensing division and they ca sell you replacement media. Which is exactly that--the media to reinstall the original OS, with no license. You'll need the COA sticker on your laptop to enter a valid installation code.
I strongly suggest this, even if you don't have Win8 or want it, because if that's what the computer shipped with, that's what the drivers were also matched to, and at some point when you want to need to restore the working OS? It may no longer be available. The disks (from Dell or MS) are often available for anywhere from $15 (MS) to $50 (some brands).

But check your premises wiring and your RF situation, your laptop should NOT be the problem, it is almost certainly just collateral damage.
 
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kennewick, wa
#14
I got in the RFI laptop kit in the snail mail today from palomar-engineers.com/rfi-kits
. The snap on ferrite split beads were to big for my cables. The beads just slide up and down the cable freely. I fixed that problem by wrapping some electric tape around the cable to increase the cable's outer dia. IT WORKED :) The laptop is happy as a clam and purring like an over stuff and spoiled kitty. There is NO MORE RFI problems with any of the laptop's USB plugins. I tried the Baofang 2m/70cm ht, the CB ht that I keep around for testing, and my Icom IC-730 HF base station. No RFI got into the laptop or the USB plugins. Now when I have the funds available to buy the MFJ-936B loop antenna tuner and build the loop antenna, then I can relay get on the air (not via a remote base) and do some digital qso's. Thanks to everyone that put some input on this subject.

Thanks for the tip on the kits.I already bookmarked the web page. And I will give it a wack when I get payed on July 3rd. And I will let you know the outcome.
 
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#15
You don't need to have the cable fill all the space inside a snap on ferrite bead. Usually one bead of any mix will have little to no effect on HF but will start to reduce RFI in the VHF/UHF range. You have to run multiple turns of your suspected wire through the snap on ferrite or have multiple beads in series to get the most benefit and the correct number of turns depends on the frequency range, the ferrite mix, and how large the ferrite is. Bob at Palomar has further information that is helpful like if you have a switching supply in the tens of KHz range, a higher permeability mix like 77 might work better at suppressing the fundamental low frequency RFI thereby killing off its harmonics at a higher frequency which is causing your problems.

I find the best results in the VHF/UHF range are passing two turns of your suspected wire through a #43 mix snap on ferrite before snapping it closed. Or use three beads in series with a single pass through them all. For HF range, passing about 5 turns through a #31 mix ferrite snap on bead is a good starting point. Passing several turns also locks the bead on the wire so it doesn't slide up and down.

Whatever the rated resistance to RF is stated for a single bead over a wire at a particular frequency, that number will be squared every time you double the amount of turns. If a bead has say 200 ohms of resistance with one pass of wire through it, two passes will be 800 ohms. At some point too many passes will be detrimental to the frequency range you want to surpress.
prcguy


I got in the RFI laptop kit in the snail mail today from palomar-engineers.com/rfi-kits
. The snap on ferrite split beads were to big for my cables. The beads just slide up and down the cable freely. I fixed that problem by wrapping some electric tape around the cable to increase the cable's outer dia. IT WORKED :) The laptop is happy as a clam and purring like an over stuff and spoiled kitty. There is NO MORE RFI problems with any of the laptop's USB plugins. I tried the Baofang 2m/70cm ht, the CB ht that I keep around for testing, and my Icom IC-730 HF base station. No RFI got into the laptop or the USB plugins. Now when I have the funds available to buy the MFJ-936B loop antenna tuner and build the loop antenna, then I can relay get on the air (not via a remote base) and do some digital qso's. Thanks to everyone that put some input on this subject.
 
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#17
All the info bellow is nice. But what you are saying contradicts the instructions that came with the snap on ferrites. In that the ferrites are not supposed to be free floating up and down the cable. The tech at Palomar Engineers told me that if the ferrite is to big for the cable then put electric tape on the cable to hold the ferrite in place. And that's what I did.

You don't need to have the cable fill all the space inside a snap on ferrite bead. Usually one bead of any mix will have little to no effect on HF but will start to reduce RFI in the VHF/UHF range. You have to run multiple turns of your suspected wire through the snap on ferrite or have multiple beads in series to get the most benefit and the correct number of turns depends on the frequency range, the ferrite mix, and how large the ferrite is. Bob at Palomar has further information that is helpful like if you have a switching supply in the tens of KHz range, a higher permeability mix like 77 might work better at suppressing the fundamental low frequency RFI thereby killing off its harmonics at a higher frequency which is causing your problems.

I find the best results in the VHF/UHF range are passing two turns of your suspected wire through a #43 mix snap on ferrite before snapping it closed. Or use three beads in series with a single pass through them all. For HF range, passing about 5 turns through a #31 mix ferrite snap on bead is a good starting point. Passing several turns also locks the bead on the wire so it doesn't slide up and down.

Whatever the rated resistance to RF is stated for a single bead over a wire at a particular frequency, that number will be squared every time you double the amount of turns. If a bead has say 200 ohms of resistance with one pass of wire through it, two passes will be 800 ohms. At some point too many passes will be detrimental to the frequency range you want to surpress.
prcguy
 
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#18
Some of the wireless keyboard/mouse combos used rf links about 30 MHz you may want to explore other options. Perhaps Bluetooth linked devices.
 
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#20
Free floating is fine if the ferrite is close to the thing that is making noise. If you must keep the ferrite from sliding down a cable and away from the noise maker then tape the wire to the ferrite or use a Ty-Rap, but you don't have to build up the diameter of the cable to fit the inside of the ferrite, that has no bearing on the ferrite doing its job in reducing noise on the wire.
prcguy

All the info bellow is nice. But what you are saying contradicts the instructions that came with the snap on ferrites. In that the ferrites are not supposed to be free floating up and down the cable. The tech at Palomar Engineers told me that if the ferrite is to big for the cable then put electric tape on the cable to hold the ferrite in place. And that's what I did.
 
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