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[Forum] Amigas causing TV interference?ANN.lu
Posted on 10-Aug-2004 05:03 GMT by Anonymous15 comments
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Has anyone noticed their A1200 causing interference on analog TV sets due to the RF connector, especially when disconnected? Looking for a way to get rid of any such interference (a terminator perhaps..) Any suggestions?
Amigas causing TV interference? : Comment 1 of 15ANN.lu
Posted by Rafo on 10-Aug-2004 03:38 GMT
Well, when you see what damage a Terminator caused to Cyberdyne,
imagine what it can do with your A1200, so it's not such a good idea.

(unless I didn't get it...)
Amigas causing TV interference? : Comment 2 of 15ANN.lu
Posted by Olegil on 10-Aug-2004 04:44 GMT
A terminator perhaps? Aka a dummy-load in ham-speak.

Also, there is a reason why the A1200 came with RF shielding. Removing parts of it to get access to something onboard WILL make the RF noise worse.
Amigas causing TV interference? : Comment 3 of 15ANN.lu
Posted by Peter Gordon on 10-Aug-2004 06:17 GMT
Wrap the whole thing in tinfoil (but be careful not to let the tinfoil touch the pins on the ports)! ;-)
Amigas causing TV interference? : Comment 4 of 15ANN.lu
Posted by Raffaele on 10-Aug-2004 07:50 GMT
An Anonymous people wrote:

>Has anyone noticed their A1200 causing interference on analog TV sets
>due to the RF connector, especially when disconnected?

Nope...


1) Perhaps, have you made modifies to the internal tin-shield of Amiga 1200 in order to force a 3,5 inch Hard Disk all into the case?

This could be a sure cause of your interference problems.

Solution 1) Insert aluminium tin-paper into the case to re-issue proper shielding.

***Be careful it must -not- touch any electrical in-charge component and keep sufficient ventilation of the air into the case***.


2) Certainly I have problems with some local TV's which disturbed the channels on which Amiga transmits. We have a lot of local TV's (ranging from those city-only transmitting upto regional networks) on UHF channels here in Italy.
But I avoided brillantly any interference by changing Amiga channel frequency.

Solution 2) Check if there is some TV channel which uses same frequencies of Amiga. The amiga cable itself due to its electrical properties could transform itself into one receiving antenna.

For example I use only ***shielded cables*** to connect it to the TV set, even when I made them by myself in order to have cables of lenghts more than 1,5, 3, or 5 meters as standard lenght of antenna-cables for sale into shops.

Solution 2b) Try to use shielded cables and MORE check carefully your house power plant if it creates noise that the couple amiga + Tv-set could amplificate.


3) Regarding noise caused by Amiga itself I can't be of any help. In Italy electrical components must pass ministerial check-test to avoid radio-interferences (and must acquire an electrical-quality-mark certified by the national electrical institution from one or more countries of EU) else they can't be sold to the public.

Amiga passed this test brillantly, and I can assure you that at my home I never suffered of any noise or interference made by Amiga or any other electrical device such as dust-cleaners, owens, telephones or else.

Fortunately I always lived in houses with good electrical power plant, all ground-shielded, and when in a old house, the entire electrical plant of the building was reconstructed recently.

However I noticed this problem in a apartment house of a friend of mine, years ago, when we played videogames with my A500. The apartment was built first than the sixties.
Good elegant house, but electrical plant into the house was built miserably, with no ground-discharge of overloads.
But then, the bad power plant it was a really danger for all the house, not only for Amiga and the TV-set.
Infacts he decided to re-built it entirely, when in the last nineties a tv-set burned out due to an overload caused by a flash during a raining.

I know that in USA it is a common problem that electrical power plants often cause problems in radio interferences, not in the buildings (which are all well controlled), but mainly in the houses built from scratch by issue of the owner.

And this is because people preferred to hire cheap wanna-be technicians instead of professional-ones, who cost alot.

[The character of the bad-technician who installed crap cables or crap bath-tubes into the walls, it is a common gag in TV sit-coms.]

Solution 3) If you lived in a house built all by carpenters and technicians hired by yourself (or hired by a previous owner of that house), you must pay a specialist to perform a whole test-check of all the power plant.

If results are bad, then you must pay to re-build entire power plant of your house. Sorry but if this is true, then is the unique solution.

Solution 3b) Or you must sell your house and move to another one, more safe and confortable.

Solution 3c) if you are in a rent-house, then contact the owner in order to provide a test-check of all the power plant... or (again) move to another place.
Amigas causing TV interference? : Comment 5 of 15ANN.lu
Posted by kalmar on 10-Aug-2004 12:35 GMT
In reply to Comment 4 (Raffaele):
Umm, the quality of house wiring has nothing to do with susceptibility of certain devices to RFI, or the emission of same from equipment. Interesting rant though!

If your A1200 is interfering with radios or TVs, it's definitely down to missing bits of shielding or unshielded or un-supressed cables coming from the computer to peripherals. I doubt it's the RF out causing the problem personally, since the radiated emission from an unterminated phono connector can't be very much at these sort of power levels.
Amigas causing TV interference? : Comment 6 of 15ANN.lu
Posted by Joe "Floid" Kanowitz on 10-Aug-2004 13:15 GMT
If you want to try a terminator, Radio Shack used to sell baggies of a few for not very much money -- just F connectors with a 75 ohm resistor on the end, and a nice metal cap over. They're also handy if you have a home distribution block (for CATV or broadcast) and want to see if you can improve anything by terminating unused outlets.

More likely is that the 1200 is simply noisy. Modern PCs 'run at' frequencies an order of magnitude higher overall, and traces in danger of radiating carry an order of magnitude less power... so a perfectly FCC certified Tandy 1000SX, classic Amiga, or even 486 may cause some noticable snow, but you can run a modern GHz machine with the case off and only interfere with your microwave, cellphones, and possibly your ability to have children. ;)

You can also play with adding ferrite cores around your power and display cords (not that I've ever had much luck with those, but you can get clip-on versions at Radio Shack for little money... and clip-on versions at a car stereo place for even less, I'd imagine)... and it'd be a good idea to check for any Class A or uncertified accessories you're using *with* the machine. (Class A ethernet hubs can get particularly noisy... but hey, that's all I could find that still offered a thinnet 'uplink!')
Amigas causing TV interference? : Comment 7 of 15ANN.lu
Posted by Raffaele on 10-Aug-2004 14:39 GMT
In reply to Comment 5 (kalmar):
Mr. Kalmar wrote:

>Umm, the quality of house wiring has nothing to do with
>susceptibility of certain devices to RFI, or the emission
>of same from equipment.

It does. Every unshielded electrical wire is like an antenna and re-transmits long its entire lenght the signal it receives.
Amigas causing TV interference? : Comment 8 of 15ANN.lu
Posted by Doobrey on 10-Aug-2004 14:50 GMT
Had a similar thing a few years ago here in the UK when they launched a new TV channel. Most VCRs/game consoles etc that used an RF connection had to be retuned to some clear space in the spectrum.
Dunno about other Amigas, but on the A1200 there`s a small tuning screw next to the RF out, try turning it until the interference goes away, then retune the TV to Amiga.
Amigas causing TV interference? : Comment 9 of 15ANN.lu
Posted by XraalE on 10-Aug-2004 22:08 GMT
Get a digital set top box for your TV. It won't eliminate the interference but you won't see it any more. And you'll get extra channels all with near-DVD quality picture and sound.
Amigas causing TV interference? : Comment 10 of 15ANN.lu
Posted by kalmar on 11-Aug-2004 06:47 GMT
In reply to Comment 7 (Raffaele):
>> Umm, the quality of house wiring has nothing to do with
>> susceptibility of certain devices to RFI, or the emission
>> of same from equipment.

> It does. Every unshielded electrical wire is like an antenna and re-transmits
> long its entire lenght the signal it receives

This has nothing to do with the *quality* of the house wiring, which is what you were going on about. Suggesting that people get their house re-wired or move struck me as bizaare and wrong advice, that's all.
In any case, it doesn't appear that the problem in the topic is caused by mains borne interference, based on the description.
Amigas causing TV interference? : Comment 11 of 15ANN.lu
Posted by Joe "Floid" Kanowitz on 11-Aug-2004 14:19 GMT
In reply to Comment 10 (kalmar):
This has nothing to do with the *quality* of the house wiring, which is what you were going on about. Suggesting that people get their house re-wired or move struck me as bizaare and wrong advice, that's all.

Well, if you go through the expense to run your wiring in shielded conduit, *and* isolate circuits, you might gain something. Is it worth it? Erm, no. ;)

Beyond that, electrical wiring is pretty much electrical wiring, though I do seem to remember some subtle aspect of most codes that avoids turning the house into a giant electromagnet/50-60Hz radiator. (For the life of me, I can't remember what exact stupidity that would be, though obviously it was found in practice for someone to bother codifying it... one hot loop with trailing neutrals?)
Amigas causing TV interference? : Comment 12 of 15ANN.lu
Posted by Raffaele on 12-Aug-2004 12:15 GMT
In reply to Comment 10 (kalmar):
Mr. Kalmar wrote:

>This has nothing to do with the *quality* of the house wiring,
>which is what you were going on about.
>Suggesting that people get their house re-wired or move
>struck me as bizaare and wrong advice, that's all.

Nope.

If thru some evidences (one of these is radio noise interferences) you discover that your house has unshielded wiring power plant and maybe not grounded also, then it is a sure danger for whole family to stay there.

Then you must or move, or to rebuilt power plant from scratch accomplishing security standards of your country.

At least this is my friendly advice.
Amigas causing TV interference? : Comment 13 of 15ANN.lu
Posted by kalmar on 13-Aug-2004 09:03 GMT
In reply to Comment 12 (Raffaele):
> If thru some evidences (one of these is radio noise interferences) you discover
> that your house has unshielded wiring power plant and maybe not grounded also,
> then it is a sure danger for whole family to stay there.

Domestic house wiring is almost never shielded. There's no requirement for it in any EU or US regulations, and never has been.

If the protective earth is floating, that's could be lethal, correct. But it's an almost un-heard of ocurrence and wouldn't have any bearing on RF interference of this sort either.

> Then you must or move, or to rebuilt power plant from scratch accomplishing
> security standards of your country.
> At least this is my friendly advice.

From the point of view of an electrical engineer, you're wrong, that's my friendly advice :)
Amigas causing TV interference? : Comment 14 of 15ANN.lu
Posted by kalmar on 13-Aug-2004 09:07 GMT
In reply to Comment 11 (Joe "Floid" Kanowitz):
Hi Joe, I think with twin-and-earth cable and ring main circuits, any such oddities become very rare.

Although I did work on an old house once where a disconnected ciruit somehow had enough energy inductively coupled into it to light a neon night-light. Bit scarey!
Amigas causing TV interference? : Comment 15 of 15ANN.lu
Posted by TheREALDanDude on 15-Aug-2004 14:35 GMT
Do you still have your aluminum cage? You need to keep that on.

Do have a grounded plug? Make sure the groud pin isn't broken. Replace the plug if it is. If you do not know how to wire a plug, >>>ASK SOMEONE KNOW KNOWS<<< INCORRECT WIRING CAN LEAD TO DESTORYING YOUR AMIGA!

Are all your cables shielded? Use shielded cables on all ports.

Are you using an indoor antenna for your TV? Perhaps consider using an external antenna like a roof fixture.

If you are considering using an all-plastic case for your Amiga, consider one that can shield against RF interference. Never leave the 2-layer backing away from motherboard. You need a plastic non-conductive layer between the motherboard and the aluminum plate, and make sure that plate is earth-grounded.
System-ground is not recommended.
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