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Author Topic: someone just kill me already....  (Read 5596 times)
3CW
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Posts: 20




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« on: January 23, 2012, 12:34:01 PM »

After finally curing severe noise problems on the grid...[the cable company is causing that problem still]...[cured that problem  by using just battery power], I've recently ran into another problem...Controlling my ICOM 7200 from the usb port brings the noise level up from s3 to about +20 on 80 and 40 meters...does anyone know if there is a cure for this?...eg; rf chokes...many thanks in advance
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WX7G
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Posts: 6197




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« Reply #1 on: January 23, 2012, 05:57:08 PM »

To drop the noise from +20 dB over S-9 to S-3 requires an attenuation of 56 dB. That is a long way to go.

If you are controlling the ICOM from a laptop run the laptop on battery power and see if the noise drops. This experiment, if successful, points in one of two directions; USB noise or power supply noise.

So let's say you performed the experiment above and the noise dropped. How do you tell if it's USB noise or power supply noise? With the power supply plugged into the laptop touch the power supply AC ground prong to the AC wall outlet screw but do not plug it in. You now have a USB common-mode noise path from the AC ground to the Icom through the laptop. If the noise comes up it is USB noise. If it does not come up it is power supply noise.

DX Engineering stocks clamp-on ferrite cores for RFI suppression.






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3CW
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« Reply #2 on: January 23, 2012, 08:30:58 PM »

thank you for that quick, informative response....hopefully I won't get too winded here, but 3 years ago a multiplexer which was part of my security system was polluting my entire property with a very loud hash noise...+40db...wiped out everything, all bands,.....once that was removed from the system, all that knocking hash disappeared....still in the system though was, [lacking a better word] a 5-7 db of a swirling noise.....tried a best selling AC in-line suppressor which reduced the noise about 3 db, but still there [+4 db]..[probably whatever the local cable company was/is using to provide internet access is causing that problem because the power company was here and cleared themselves...lol..

Finally I switched to battery power [off the grid completely]....noise was virtually eliminated .. maybe .5 to 1 db atmospheric [these readings were all in the yard or in an extension room out back]....but whenever I take these radio's into a room upstairs [on battery power], whether a computer is in the room or not, certain sections of the rooms generate some heavy noise....20-30 db mainly 40 and 80m......

So what I did was I took the Icom to the noise free room in the back of the house.....I then ran a 30 foot USB extension cable to the computer upstairs.....without the usb cable even plugged in to the computer, immediately plugging the usb cable into the rig brings the noise back to +10db......the guy at Icom said the 30 foot long usb cable was probably picking up noise acting like an antenna....all that being said, will your suggestion of clamp-on ferrite cores for RFI suppression do the trick?....if so can you be specific on model numbers and actual placement of these things...sorry to say I have NO experience with the cores, which you are probably already aware of.....

thanks so much!
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K1CJS
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« Reply #3 on: February 02, 2012, 04:53:20 AM »

Any time you have long wire connections that can act as antennas, they will.  Shielded cable is the one exception--and even then, that cable can still induce problems.

If I may be so bold, you still haven't indicated which kind of computer--whether desktop or laptop.  Sometimes laptop power adapters are little better than wall warts (AAMOF some of them ARE wall warts) and the desktop computers have cheap, foreign made power supplies in them.  

I'll never forget the one example I experienced where I bought a computer case with a power supply already installed--and had horrendous noise generated that I finally tracked to that power supply (a 'hong sang' special).  After buying and installing an Antec computer power supply (at almost twice the cost of the tower case and power supply combined) the noise vanished.

The cause can be more than just one thing too.  It wouldn't surprise me if you finally found that the power supply AND the cable were contributing to your woes.
« Last Edit: February 03, 2012, 08:46:56 PM by K1CJS » Logged
AG6WT
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Posts: 474




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« Reply #4 on: February 03, 2012, 08:14:01 AM »

You didn't say what band but a 30 foot usb cable is almost a 1/4 wave length on 40 meters. That's not good as it will be very sensitive to RFI. Here are few things to try:

1) Ferrite cores.

2) Ground the USB cable shield at the radio end. Grounding at multiple points along the length is better.

3) Use a quality powered USB hub. Some better hubs provide some level of isolation.

4) Use an USB optical isolator. These aren't common.

4) Put the computer controlling the Icom next to the radio. Then control that computer remotely with a second computer using wi-fi and a remote desktop software like VNC.

5) Get a wireless USB extender.
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3CW
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« Reply #5 on: February 09, 2012, 07:49:30 AM »

Hey guys, thanks for the continued response...Just an update here....I have now tried 4 different computers [1 laptop] and the computers were connected this time at a distance of only 6-10 foot of usb cable.....[not the 40 foot run like the first time]...no change whatsoever....noise is still being generated at +9-10db min mostly 40 -80 meters....I guess I need to try ferrite cores [not sure even where they go] and grounding the usb shield....thanks again.....this is a crazy age for rfi now that computers and switching ps's are everywhere....
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KC2RGW
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« Reply #6 on: February 09, 2012, 11:50:38 AM »

So.... connect the radio to the computer right next to it and use a remote desktop software on the remote laptop to connect to the computer and work digi.  Unless maybe the laptop is your only computer?
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3CW
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« Reply #7 on: February 09, 2012, 07:35:57 PM »

Hello KC2.....getting the noise irregardless of the distance between the computer and radio....currently have 3 desktops and 1 laptop....all are generating the +9 to +10db noise
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K1CJS
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Posts: 6055




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« Reply #8 on: February 14, 2012, 04:56:08 AM »

If you still have the noise with the different computers, the problem more than likely isn't with the computers.  Have you checked your router and/or modem?  Less expensive network cable isn't shielded, and either the modem or the router can be the source of noise--propagated along that cable.

Quite a few of us have found that the wall warts that their modems/routers run off of is the source for noise that the modem/router actually amplifies and distributes.  I did--and I cleared it up by using a couple of older CB radio power supplies to power the modem and router in my home--their output is a lot cleaner than most wall warts by far.

If you are able to, (that is if your modem/router runs off 12 VDC) run your modem/router off a 12 v battery to see if the wall wart is the source of the noise you're getting.  Good luck and 73!
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