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Author Topic: RF in computer  (Read 2331 times)
KE4AIF
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Posts: 60




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« on: July 08, 2018, 05:18:10 PM »

When I run my amp on HF my computer might lock up or have any number of kinks.
I have all of my equipment going to an earth ground with several rods.
Where should I start? Thanks Billy
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KC9NVP
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Posts: 307




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« Reply #1 on: July 08, 2018, 05:28:17 PM »

So little information to go with, it will be a shot in the dark.  But some questions first. 
What is your setup like, computer connected to radio thru a interface cable?
How close are the radio, computer, amp to each other? 
Radio model?
Amp model?
Computer model?
What type of antenna are you using?
How close is the computer to the radio and Amp? 
Where is the antenna located? 
What type of feed line are you using?


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NK7Z
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Posts: 2514


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« Reply #2 on: July 08, 2018, 06:01:32 PM »

Hi,
See:
https://www.nk7z.net/rfi-now-house-cleaning/
I have a three part article on removing RFI from your Amateur Radio environment.  It may help some...  Look on the right sidebar for more articles dealing with RFI...
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
KE4AIF
Member

Posts: 60




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« Reply #3 on: July 08, 2018, 08:46:41 PM »

What is your setup like, computer connected to radio thru a interface cable? No
How close are the radio, computer, amp to each other? All on a 6 foot folding table
Radio model? TS-2000 and FT-950
Amp model?  AL1500
Computer model? Dell with windows 7 About 10 yrs
What type of antenna are you using? Cage dipole on 75-dipole on 40-beam 20,15,10
How close is the computer to the radio and Amp? around 3 feet
Where is the antenna located? over my house at about 50 feet
What type of feed line are you using? RG-213
Thanks Billy
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K5LXP
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Posts: 6147


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« Reply #4 on: July 09, 2018, 04:40:54 PM »


Step one, do a survey where you determine what bands and power levels the problem happens.
Step two, make a change.  That can be ferrites, cable routing, adding a choke unun, what have you.
Step three, re-run the survey. 

One of three results may be observed:

The amount of power it takes or the frequencies where the problem happens improves.  You know you're barking up the right tree as far as mitigation. 

Another is nothing improves.  While not what you want to see, you know that whatever you tried isn't where the problem is so try something different. 

Lastly, it can get worse, i.e. the problem happens at lower power or more frequencies.  Almost as good as getting better, because you're on to where the PC is sensitive.

Mark K5LXP
Albuquerque, NM
 
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KE4AIF
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Posts: 60




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« Reply #5 on: July 10, 2018, 01:31:27 PM »

WHat kind of ferrites and where do you buy these?
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W8JX
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Posts: 13268




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« Reply #6 on: July 10, 2018, 04:23:11 PM »

I would suggest 1, replacing computer as newer ones are better with RFI and 2, move antenna away from house. WHen you run a amp with a antenna over house you "light" your house up with a very strong RF field. Its amazing when you do not have problems.
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
K5LXP
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« Reply #7 on: July 10, 2018, 04:55:17 PM »


WHen you run a amp with a antenna over house you "light" your house up with a very strong RF field. Its amazing when you do not have problems.

It certainly does make the problem harder to solve.  Even otherwise shielded equipment can become susceptible given enough field strength.  In another thread I called it "You're sitting in a swimming pool and asking for an umbrella."

But, you don't know until you understand the scope of the problem and trying some basic mitigation methods.  Sometimes you luck out and you find just re-routing cables or adding a ferrite or two does the trick.  Mostly luck to be sure but you don't know until you do the survey, try something and see the effect.  In the case of just plain overload, JX's suggestion might be easier than shielding, choking, bypassing and bonding everything in sight.

Mark K5LXP
Albuquerque, NM
 
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KE4AIF
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Posts: 60




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« Reply #8 on: July 10, 2018, 10:09:24 PM »

Problem seems to be at 7 MHZ and below. Any ideas on some kind of ferrites I could use and where to get them and where to attach them?
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K5LXP
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« Reply #9 on: July 11, 2018, 08:21:14 AM »


Have you tried isolating it to a particular input, like the keyboard, mouse, network, monitor, etc?  Also, be mindful of ground loops and just general cable dress issues.  You may find it's not an equipment fault but just an increased susceptibility from your specific installation.

Here's a ham supplier of ferrites.  Also some application information.

http://www.kf7p.com/KF7P/Ferrite_chokes.html

Mark K5LXP
Albuquerque, NM
 
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W8JX
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« Reply #10 on: July 11, 2018, 08:35:50 AM »

Problem seems to be at 7 MHZ and below. Any ideas on some kind of ferrites I could use and where to get them and where to attach them?

That would suggest that RF is getting in through AC power wiring.
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W9IQ
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Posts: 3415




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« Reply #11 on: July 11, 2018, 08:57:47 AM »

Type 75 ferrite material is good for this frequency range. Toroids are commonly available. Buy a half dozen or so and apply them to any cable attached to the computer including power, network, keyboard, mouse, monitor, etc. Get large enough toroids so that you can wrap at least 4 turns (more is generally better) through the toroid without having to remove any connectors from the cables. Wind them such that the toroid is as close to the computer as possible.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
WB4SPT
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Posts: 777




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« Reply #12 on: July 11, 2018, 11:06:59 AM »

Problem seems to be at 7 MHZ and below. Any ideas on some kind of ferrites I could use and where to get them and where to attach them?

That would suggest that RF is getting in through AC power wiring.

agree with this.   At this freq, direct effects are unlikely;  the signal is coming in via wires.  AND, the correct ferrite is likely to fix this. 

 "Dell" is not descriptive enough.   Laptop or desktop?   How many wires are entering the PC? 
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KE4AIF
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Posts: 60




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« Reply #13 on: July 11, 2018, 09:20:25 PM »

This is a Desktop
Wires going into computer are Monitor - A/C - Modem - Wireless keyboard and mouse
Thanks Billy
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WB4SPT
Member

Posts: 777




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« Reply #14 on: July 12, 2018, 09:00:11 AM »

This is a Desktop
Wires going into computer are Monitor - A/C - Modem - Wireless keyboard and mouse
Thanks Billy

try without the modem connected at the Dell.  Insure the VGA cable is shielded at the DB15 connector(s). 
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