Which computer do I need?

[Rob]

radio frequency interference

 

[Gav Peter]

Cool - what does that do to my prospective carputer? How is it caused, how does it manifest itself & how do I get rid of it if it occurs?

Big lead box??? ;-)

 

[Jon Wildsmith]

usually it's the computer producing RFI and causing problems with your radio, not the other way round Crispin has been having trouble with his carpc and what sounds like his radio being desensitised by the RFI being quite strong. Components that produce less RFI and a case with better shielding would probably help.

 

[Andy Harvey]

Basically RFI is caused by anything electrical that can emit magnetic / electrical waves. All electrical items emit to some lesser or greater extent magnetic waves caused by the carriage of electrical charge within them. Basically a radio transmitter is a controlled RFI generating device, but instead of emitting Radio frequencies that you don't want (noise / RFI) it emits radio frequencies that you do want and have control of. Mainly caused by Motors / fans and transformers, Can also be caused by cables running close to other cables carrying electrical current. RFI can cause noise or reduction in performance in electrical or data circuits. A relatively common one is in houses these days with telephone cables running close to electrically noisy low voltage transformers for lighting. Can really screw up your broadband signal and may or may not be audible on the telephone lines. Magnetic waves passing into cables generate the movement of charge and therefore electrical noise which can be picked up as power spikes or noise depending on the purpose of the circuit. A known extreme form of RFI is the electric pulse caused by an Atom bomb explosion which can really damage electrical circuits with massive power spikes.

Shielding basically reflects the RFI back on itself and contains it within the component that produces it (however this can also cause additional heat which is why possibly some items are not adequately shielded. Because cables themselves can generate RFI (good shielding insulation can minimise this a lot) reduction in interferance is why it is best to run a car radio and a CB or Amateur radio rig on a separate circuit from anything else. It's also why running data cables away from mains cables is a good idea in the house.

So to get rid of it.

1. Make sure noisy components (fans and transformers mainly) are shielded.
2. Use good quality cable for wiring up sensitive things like radios
3. Use an inline noise filter on the power lead to the radio or wire the radio to a clean direct battery connection and a clean earth straight off the battery.
4. Use an antenna RF filter if the RFI is coming in via the antenna or make sure the antenna has a good earth.
5. Make sure any affected circuits wire to a clean earth from the battery rather than the chassis earth as the body will carry a lot of RF interferance around the vehicle.

Best thing though these days is to use decent components in the computer rather than some of the cheap budget ones that can emit a lot of electrical noise.

Remember bottom line is that any electrical component or cable carrying current emits magnetic radiation to some extent outside the component or cable. Any magnetic wave coming around an electrically conducting device will generate current (the reverse of the first thing) so the best key to minimising RFI is to either stop the magnetic waves getting out of the device or cable (shielding) or stop the magnetic radiation getting into the cables (shielding again). The last option should be getting rid of it once it has been caused which is done with filters.

 

[Chas]

My laptop has died on me, so I've just got one of these on eBay, a Panasonic Toughbook;

They say they can be run over be a 4x4;

http://www.youtube.com/watch?v=N53xYt_Q ... re=related

but I don't think I'll risk it
Chas

 

[Andy Harvey]

Chas.

good man, a CF-28 (or is it a CF-29, I think that the 29 looks a littel different and that looks like mine), you bought the best. Yes you can run a Hummer over it - it has been done, and it will even stop a bullet (as long as it isn't point blank) again it has been proved. Bomb proof, Waterproof, dust proof, drop proof, they really are the most rugged of the rugged.

I have one of those with internal WIFI, Bluetooth, 3/4 gig memory, 120gig hard drive, 13.3 inch touch screen and also a Wireless remote touchscreen and a Car docking station.

Have a search for Notebook forums, there is a Toughbook forum on there which has lots of usefull info and some really excellent helpful guys.

 

[Chas]

Chas.good man, a CF-28 (or is it a CF-29, I think that the 29 looks a littel different and that looks like mine), you bought the best. Yes you can run a Hummer over it - it has been done, and it will even stop a bullet (as long as it isn't point blank) again it has been proved. Bomb proof, Waterproof, dust proof, drop proof, they really are the most rugged of the rugged.I have one of those with internal WIFI, Bluetooth, 3/4 gig memory, 120gig hard drive, 13.3 inch touch screen and also a Wireless remote touchscreen and a Car docking station.
Have a search for Notebook forums, there is a Toughbook forum on there which has lots of usefull info and some really excellent helpful guys.

It's a PANASONIC TOUGHBOOK CF-28 with 40GB HDD and 1.44MB FDD, Magnesium Encased Cabinet, 13.3 Transflective TFT Colour LCD, meets MIL spec for Shock, built in WiFi, backlit Rubber keyboard and touchpad, mains power supply and a free CD drive all for the princely sum of £400 inc P&P
Chas

 

[Andy Harvey]

Excellent, got the waterproof keyboard as well. If you want a bigger hard drive you can fit a normal 2.5 inch ATA drive (5400 or 7200 rpm) into the drive caddy. Is it running XP or W2K?.

 

[Chas]

Excellent, got the waterproof keyboard as well. If you want a bigger hard drive you can fit a normal 2.5 inch ATA drive (5400 or 7200 rpm) into the drive caddy. Is it running XP or W2K?.

Hi Andy,
I think the 40Gb will do for now, it's running XP Pro, I've got a Toughbook CF-48 already that's just thrown a wobbly, which is why I've gone for this one, it's a bit more rugged than the CF48, I'll get that repaired and put it on eBay
Chas

 

[Andy Harvey]

I also have a 51 which it took me ages to get right but eventually got working which I now use as my main desktop machine as it is faster and more powerful for everyday use - I do a fair but of my work on that machine when I want a decent screen and to have muliple documents open - the 28 creaked a bit with that although it still worked very reliably. I have to say the 28 has been the most reliable machine I've ever had with not one minute of problems in 3 years of ownership despite putting a fair few bits on afetr I got i - rubber keyboard, touch screen, internal wifi and bluetoth etc. I have to say Bluetooth is the one thing I'm missing on the 51 - going to get one of the short PCMCIA cards that you can put in the slot and it doesn't protrude at all - that's basically the same as I have in the 28 but put in the 3rd PCMCIA slot which is actually behind the ethernet port and fully internal (often used for the internal WIFI when it is on a PCMCIA card (mine is on a combo modem / WIFI min PCI card under the battery and wired out to the CDMA antenna which works OK for short distances but isn't really the right length for a WIFI unit if you want to get anything more than about 30 metres signal.

 

[Chas]

My laptop has died on me, so I've just got one of these on eBay, a Panasonic Toughbook;

They say they can be run over be a 4x4;
http://www.youtube.com/watch?v=N53xYt_Q ... re=related
but I don't think I'll risk it Chas

If anyone else is considering getting one of these the seller has more

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0445122618

the bid price is open to offers, I offered £400 which was accepted, so go on Fill your boots
Chas