Dear all members, I would appreciate any comments with a view to eradicating the following problem: I am getting interference on my PC while transmitting on the 15m band.It manifests itself by a dimming of the screen and in addition there is an audible oscillation from inside my PC tower on the motherboard.This audible tone is similar to the tone produced when the RAM chips are not properly secured.I have recently had to replace the RAM (due to crashing of the PC) and I suspect, but cannot be sure,that the RAM chips may have been corrupted by the RF signal from my Kenwood Ts440s which is about 2m from my PC.So far I have only found it to occur on the 15m band. Many thanks in advance for comments, Peter.
RF Interference on PC
- Thread starter radioscope
- Start date
Hiya Peter.
I'll start by stating the obvious, clearly RF current is somehow getting in to the PC enclosure, but how is the question...
What concerns me about your description is the fact that not only is the RF energy affecting the PC itself, but also the monitor
It could be RF getting into the graphics card causing the monitor to appear dimmer, by altering the brightness (chroma?) level, but more alarmingly it could be that there is so much RF energy flying around your shack that it is directly causing problems with the monitors power supply and/or associated circuitry.
The noise you mention from within the PC tower itself would at a guess be either RF causing problems with the towers switch mode PSU, causing it to 'squeg' (audible mechanical oscillation), or it might be direct breakthrough on the towers alarm speaker/sounder (the one used for bios beeps etc.)
Having said all of the above, and the fact that you say it only occurs when you are operating on the 15m band, I would suggest that you problem lies in your antenna system, with either the feed method or grounding system being to blame. As you change bands/wavelength so the points of current maxima will shift accordingly.
Rather than run through every possibility, can you supply further info about your system?
Mainly:
Best 73, Mark.
I'll start by stating the obvious, clearly RF current is somehow getting in to the PC enclosure, but how is the question...
What concerns me about your description is the fact that not only is the RF energy affecting the PC itself, but also the monitor
It could be RF getting into the graphics card causing the monitor to appear dimmer, by altering the brightness (chroma?) level, but more alarmingly it could be that there is so much RF energy flying around your shack that it is directly causing problems with the monitors power supply and/or associated circuitry.
The noise you mention from within the PC tower itself would at a guess be either RF causing problems with the towers switch mode PSU, causing it to 'squeg' (audible mechanical oscillation), or it might be direct breakthrough on the towers alarm speaker/sounder (the one used for bios beeps etc.)
Having said all of the above, and the fact that you say it only occurs when you are operating on the 15m band, I would suggest that you problem lies in your antenna system, with either the feed method or grounding system being to blame. As you change bands/wavelength so the points of current maxima will shift accordingly.
Rather than run through every possibility, can you supply further info about your system?
Mainly:
- What antenna/s do you use for 15m?
- What grounding system do you use if any?
- Is the Radio directly connected to the PC in any way?
- At what power levels and modes does the problem occur?
Best 73, Mark.
Last edited:
Hi Mark, First of all many thanks for replying to my questions and for the helpful comments which prompted me to investigate further the problem of RF getting into my PC.By a process of elimination and checking leads connected to the PC while on transmit,I found that Rf was getting into the PC via the keyboard which was picking up the signal.I only have a mains and waterpipe earth and couldn't cure the problem with earthing.Eventually I wrapped the keyboard lead around a ferrite ring making an RF choke which did the trick.I found also that the mouse was inactive due to the RF and again was cured by putting an RF choke in the mouse lead.It's always useful to have a couple of ferrite rings handy!As for the monitor that seems to be OK and interference must have occurred at a very particular frequency.My output power is 100watts.
You are quite right I believe in suggesting it may have been a feeder problem (my antenna is a half wave G5RV).I have been using a balanced 300 ohm feeder which was not actually balanced due to the proximity of the antenna to nearby objects and hence the feeder was radiating near the shack even though it shouldn't radiate.So recently I changed to a coaxial feeder and making a balun by coiling the coax near the feed point.I must say however that my G5RV doesn't work nearly as well (thus far) using coax instead of 300 ohm ribbon cable.My next step to improve it will be to use a 4:1 balun to help match the coax to the matching stub of the dipole.
Lastly,what is your opinion regarding the presence of lots of RF in the shack and one's physical health?
Thanks again,best 73
Peter
You are quite right I believe in suggesting it may have been a feeder problem (my antenna is a half wave G5RV).I have been using a balanced 300 ohm feeder which was not actually balanced due to the proximity of the antenna to nearby objects and hence the feeder was radiating near the shack even though it shouldn't radiate.So recently I changed to a coaxial feeder and making a balun by coiling the coax near the feed point.I must say however that my G5RV doesn't work nearly as well (thus far) using coax instead of 300 ohm ribbon cable.My next step to improve it will be to use a 4:1 balun to help match the coax to the matching stub of the dipole.
Lastly,what is your opinion regarding the presence of lots of RF in the shack and one's physical health?
Thanks again,best 73
Peter
Hiya Peter
I'm glad you managed to solve your PCI(?) problem!
Ferrite rings are always useful, and so to are the clamp-on ferrites available these days. I find the clamp on ferrites easier to use on keyboard, mouse, microphone and data cables.
RF energy is funny stuff, with high levels at low frequencies seemingly OK, but the same energy level at VHF and UHF frequencies could cause problems in the long run.
RF energy is classed an a non-ionising radiation, so in theory we have nothing to worry about as regards molecular changes in our body, but, RF energy such as that found around the average shack could cause problems in other ways.
For example, a high RF level at say 144MHz could induce quite high currents to flow close to the surface of your skin. Someone who is about 5'10" might have at least two high current areas (the person would be about one wavelength tall, so a high RF current would exist at the centre of each halfwave), and depending upon how they were sitting might have other current peaks somewhere around their elbows (about a half wave along each arm) etc.
A few watts shouldn't hurt anyone, but if you were using a high gain amplifier and sitting close to say a collinear antenna then you could experience localised heating of body tissues. The main problem with heating such as this is that if the cells become too hot then there is a chance of either causing cells to die, or bringing about a mutation (for want of a better word) of the cellular structure. This can lead to cells multiplying more often than they should, cells becoming larger than they should, cells storing more materials than they should and so on.
At higher frequencies (microwave ones) such as 10GHz, localised heating can occur in vital areas such as the surface of the eye. At the time this occurs you may not feel anything much more than a slight dryness of the eyes, but again the danger is that one the localised heating has taken place you could end up with cataracts a few years down the line.
There are many published guidelines as to what is supposed to be safe and what isn't, but I would say the absolute minimum exposure is best of all.
I once operated with a magnetic loop antenna about two or three feet away from me. The magnetic loop was fairly small, only about one and a half feet in diameter, and I was only running about two watts or so of power on 10m. About two hours after I started working stations with that setup I began to feel quite sick, and developed the worst headache I have ever had. I felt as though my head would split in two! I took that as a 'warning' and NEVER operated in such a manner again.
Even when I use VHF and UHF handhelds I always try to operate them via a speaker mic so that I can keep the antenna away from my face.
Some might say that I'm over-cautious, but better safe than sorry!
With HF RF energy the problem isn't so much direct i.e. you do not need to worry so much about induced currents due to resonance, but what you do have to watch out for is direct paths into yourself.
For example, if you have a long wire antenna and your earth connection isn't the best, you are likely to have RF energy flowing into and over any equipment that is connected to the transmitter. Lets say you now decide to use a metal bodied base microphone, and you operate with one of your hands around the mic. We have now created a path for the RF current to flow into your body, either by capacitive or direct coupling. So, not only will RF energy flow into and over the surface of your body (you are a living capacitor!), if you have your feet resting flat on a conducting surface you will again be providing a path of low reactance for the RF energy to flow through.
Again, don't let me frighten you with the above comments, but if you tend to sit there with a 1KW amplifier running all the time and you sit only a few feet away from the antenna, then clearly there is more 'potential' for health problems than if you were running say 20 watts from an antenna that is situated 30-40 feet away.
RF energy is sneaky in that you very often only notice the affects when it's too late, unless you happen to touch the HT line of a large tube amplifier in which case the effects are much more sudden and noticeable!
I'm glad you managed to solve your PCI(?) problem!
Ferrite rings are always useful, and so to are the clamp-on ferrites available these days. I find the clamp on ferrites easier to use on keyboard, mouse, microphone and data cables.
RF energy is funny stuff, with high levels at low frequencies seemingly OK, but the same energy level at VHF and UHF frequencies could cause problems in the long run.
RF energy is classed an a non-ionising radiation, so in theory we have nothing to worry about as regards molecular changes in our body, but, RF energy such as that found around the average shack could cause problems in other ways.
For example, a high RF level at say 144MHz could induce quite high currents to flow close to the surface of your skin. Someone who is about 5'10" might have at least two high current areas (the person would be about one wavelength tall, so a high RF current would exist at the centre of each halfwave), and depending upon how they were sitting might have other current peaks somewhere around their elbows (about a half wave along each arm) etc.
A few watts shouldn't hurt anyone, but if you were using a high gain amplifier and sitting close to say a collinear antenna then you could experience localised heating of body tissues. The main problem with heating such as this is that if the cells become too hot then there is a chance of either causing cells to die, or bringing about a mutation (for want of a better word) of the cellular structure. This can lead to cells multiplying more often than they should, cells becoming larger than they should, cells storing more materials than they should and so on.
At higher frequencies (microwave ones) such as 10GHz, localised heating can occur in vital areas such as the surface of the eye. At the time this occurs you may not feel anything much more than a slight dryness of the eyes, but again the danger is that one the localised heating has taken place you could end up with cataracts a few years down the line.
There are many published guidelines as to what is supposed to be safe and what isn't, but I would say the absolute minimum exposure is best of all.
I once operated with a magnetic loop antenna about two or three feet away from me. The magnetic loop was fairly small, only about one and a half feet in diameter, and I was only running about two watts or so of power on 10m. About two hours after I started working stations with that setup I began to feel quite sick, and developed the worst headache I have ever had. I felt as though my head would split in two! I took that as a 'warning' and NEVER operated in such a manner again.
Even when I use VHF and UHF handhelds I always try to operate them via a speaker mic so that I can keep the antenna away from my face.
Some might say that I'm over-cautious, but better safe than sorry!
With HF RF energy the problem isn't so much direct i.e. you do not need to worry so much about induced currents due to resonance, but what you do have to watch out for is direct paths into yourself.
For example, if you have a long wire antenna and your earth connection isn't the best, you are likely to have RF energy flowing into and over any equipment that is connected to the transmitter. Lets say you now decide to use a metal bodied base microphone, and you operate with one of your hands around the mic. We have now created a path for the RF current to flow into your body, either by capacitive or direct coupling. So, not only will RF energy flow into and over the surface of your body (you are a living capacitor!), if you have your feet resting flat on a conducting surface you will again be providing a path of low reactance for the RF energy to flow through.
Again, don't let me frighten you with the above comments, but if you tend to sit there with a 1KW amplifier running all the time and you sit only a few feet away from the antenna, then clearly there is more 'potential' for health problems than if you were running say 20 watts from an antenna that is situated 30-40 feet away.
RF energy is sneaky in that you very often only notice the affects when it's too late, unless you happen to touch the HT line of a large tube amplifier in which case the effects are much more sudden and noticeable!
Hi Mark, Many thanks again for your comments re: RF and health. You drew quite a vivid picture of what RF can do and I intend to play it safe and stick to my coaxial feeder where the radiation is much less than with the 300 ohm twin I was using. As you say better be safe than sorry. I was talking about this issue with a friend recently and wondered if a survey has ever been done to ascertain whether radio amateurs suffer health problems beyond the norm.
Best 73
Peter
Best 73
Peter
Hiya Peter
Well, it has been noticed/suggested that Amateur Radio operators suffer from a higher rate of heart attacks.
This was put down to MF & HF signals upsetting the bodies natural heart pacemaker. Personally I think that the increased level of heart attacks is more likely due to the fact that most Hams prefer to play in their shacks rather than going for a jog, and in past times there were a high number of smokers (and drinkers) among our ranks.
So no exercise + booze + cigarettes = early visit to the shack in the sky!
On a similar tack, I once read a book by a pathologist called something like "The Mysteries of Life & Death". In that book there was a section on suicide, and a chart of suicide rates versus occupation. Top of the list of folks most likely to commit suicide were....
Radio Operators!
Oh well, "By the time you read this..." hi hi
Best 73, Mark.
Well, it has been noticed/suggested that Amateur Radio operators suffer from a higher rate of heart attacks.
This was put down to MF & HF signals upsetting the bodies natural heart pacemaker. Personally I think that the increased level of heart attacks is more likely due to the fact that most Hams prefer to play in their shacks rather than going for a jog, and in past times there were a high number of smokers (and drinkers) among our ranks.
So no exercise + booze + cigarettes = early visit to the shack in the sky!
On a similar tack, I once read a book by a pathologist called something like "The Mysteries of Life & Death". In that book there was a section on suicide, and a chart of suicide rates versus occupation. Top of the list of folks most likely to commit suicide were....
Radio Operators!
Oh well, "By the time you read this..." hi hi
Best 73, Mark.