[Ham-Mac] RFI getting into computer

[Richard Hemingway]

Hi Steve,

Thank  you very much for your insightful comments.  I really appreciate them.

>I hope you understand that it will always be a battle with an 
>antenna so close to your computer.  Actually I worry more about you 
>own personal exposure to such high RF radiation levels over a 
>prolonged time!!

Yes I understand that, however, it is either that or nothing!

>Don't kid yourself 30 watts on PSK is a lot.  Typical transceiver 
>today has a fairly low duty cycle. PSK, RTTY and digital modes work 
>your finals very hard.  I only use 25 watts on my Kenwood which is 
>rated for 100w peak.  These digital AFSK mode send without pauses 
>which you would find in voice or CW.

I really don't transmit very much.  I listen a lot.  I doubt if 
actual TX would add up to even 15 minutes any particular day.  I also 
don't operate every day.  My power varies from 25 to 30 watts, 
depending where I set it. Thank you for your concern.

>Some of the Macs/Apple monitors, but not all, have touch sensitive 
>switches.  My old G4 cube had one.  They are more susceptible to 
>strong RF than a physical switch.  Like a laptop trackpad they 
>measure capacitance changes.  That's how they tell if your finger is 
>one them.  Strong RF will change the capacitance field make it think 
>you put your finder on the button.  Hence why you Mac turns off or 
>goes to sleep (Depending on your systems settings).

Yes the monitor, a 15"  studio display about three years old, does 
have a pressure switch on the left side for brightness.  When RF gets 
into the monitor the Apple Studio Display lights up.  So you are 
right about this.

>iMac G5 and iMac Intel Core Duo have a push button switch.  So you 
>should be ok.
>
>Todd is correct. All plastics have an RF "paint" sprayed on them but 
>this is to minimize RF getting out of the computer not really design 
>to prevent heavy RF getting in.  There is no manufacture of 
>computers that test strong RF signal like 30 watts or more at 10 
>feet away. Heck a wireless base station or card uses less than 50 
>Milliwatts.

I thought that the RF "paint" was a joke. I didn't know such a thing 
existed!!  My profound apologies to Todd.

>
>RF is getting into all parts of your computer. The amount depends on 
>many variables including, as you noted, its position relative to 
>your antenna.  At the right TX frequency and TX pattern you could 
>actually be interfering with the computer CPU, memory, power supply, 
>hard drives, USB hubs and more. I would use a separate ground, if 
>possible, for your antenna and liberal use of Ferrite cores on all 
>monitor, power and audio cables to reduce RF getting into 
>electrical. Would not put them on USB/Firewire as that seems to 
>cause problem with their ability to transfer data.

I am liberally using Ferrite cores on all cables.  The only ground 
available to me here is the third wire ground in the power 
outlet.Thanks for the USB/Firewire comment.

>You are going to have to be quite forgiving of all electrical 
>equipment in your close proximity and take some time to work it out. 
>Even the change in TX frequency, band, SWR of your antenna will have 
>different effects.  And again I will stress be careful of your own 
>personal exposure to high and prolonged levels RF.
>
>Looking forward to hearing your experiences with the new computer.

It is on the way and will be here about Monday.  Then I can get to 
the job of migrating all my programs to the new iMac and zero erasing 
the HD of the G5.

BTW where is Pickering, Ontario?? My parents were both from Ontario. 
I was born in Detroit before they were naturalized  Spent every 
summer in Canada. I guess I could have dual citizenship. I wear a 
Canadian Pride T shirt around here.

Take care and thanks,

73, Dick, N5XRD