[plug] Sources of interference - was Please help.. i'm desperate

[Kai]

Mark J Gaynor wrote:

> 
> *********** REPLY SEPARATOR  ***********
> 
> On 21/09/2003 at 12:08 PM Sham Chukoury wrote:
> 
> 
>>Another possibility is a nearby AM radio station, or bandit ham radio
>>operator that are disrupting the DSL signal since they operate in a
>>similar frequency range. These may only cause problems at certain times
>>of day, like when the station boosts its signal at night. A good telco
> 
> 
> This is a myth. If you know anything about radio transmission you would
> not make such a statement. Radio reception changes at night due to the 
> layers in the atmosphere changing. Nothing to do with transmitter power levels.

I used to live in Rochester Circle, Balga, just across the road from 
that lovely 300' (?) tall ABC radio national transmitter, which put out 
some cruel wattage...around 4kW afaik, plenty of power to be absorbed 
into the surround telephone lines and cause interference.
When I was on dial-up connection I couldn't keep the connection for more 
than, say, 5 minutes, before the line would drop. I know the transmitter 
was put there long before the day when that area was rezoned as 
residential but the output power remains the same and if we picked up 
the telephone handset (or if I listened to my Banksia Wave SP modem 
speaker) I could hear 6WF quite clearly above the dial-tone !

I know this is different to ADSL (difference in used frequencies for 
ADSL and modem/voice) but I overcome the problem by getting a filter off 
Telstra...the filter was pre-moulded and I didn't want to break the 
mould and have a look inside but I'm guessing they had some sort of 
toroidal bailun in there which supressed the line noise and made my 
connection work wonderfully.

>>DSL tech may be able to help minimize the impact of this.
> 
> 
> Sham,
> I would be careful what you say about AM radio stations or Ham Radio 
> Operators. They have to jump through hoops to get their licence and they
> take great care that their equipment meets ACA standards. Not like the
> class license that CB Radio Operators get free. In may cases it has been
> proven that the Amateur Radio equipment exceeds the required RFI Standards,
> and that the affected equipment is poorly designed and/or manufactured.
> 
> It is a well known fact that to get prices down to market expectations, the 
> manufacturer will skimp on RFI filtering to cut costs. It is generally the first thing
> to go as it makes little or no difference to performance. This is true for devices
> that radiate potential RFI too, like microwave ovens. Just because a modem is
> new and works well in most cases does not mean that the modem is well 
> designed or built. You have to remember that ALL consumer merchandise is
> MADE TO A PRICE and NOT TO A STANDARD. This is why consumers generally
> don't get the type of equipment that will be immune to the environment it is placed
> in - its just too expensive and price is everything to a domestic consumer. You get
> what you pay for, and in some cases it not what you want or need.
> 
> I do agree that you must take a close look at the environment, BUT DON'T start
> pointing the finger at a general community without due reason. If you consider
> Ham Radio as a problem, I suggest that you do better research. You might find the
> CB community cause more problems that Ham Radio Operators are blamed for. 
> The lack of understanding what causes RFI is the biggest problem. Even you might
> be surprised.
> 
> I speak from experience, I am an Amateur Radio Operator of many years experience
> and have a good understanding of computer and electronic equipment in general. I
> also worked in mainstream Television for over two decades in technical areas. You
> have a better appreciation of what constitutes RFI and the lengths you go to eliminate it.
> Your mobile phone is one such source. If you want a great source of RFI, pick any
> domestic computer or better still a fluorescent lamp with the power factor capacitor removed.

Mark's dead right, I'm also a licensed amateur radio operator, the 
amount of study, regulations and electrical theory you need to learn and 
the regulations and operating procedures we're governed by means we have 
to make things to strict guidelines or we're not allowed to use it.
CB'ers and "superior equipment" operators (ie CB'ers who use amateur 
radio equipment) who use illegal operating hardware really get up my 
nose - I studied hard for my license and for the right to build and use 
the equipment, they go to some (dodgy) retailer and pay a bit extra for 
the privelage to use superior equipment and power levels and if someone 
complains of RFI on the TV or voices on the phone line, guess who'll be 
the first people to get the blame even if they have nothing to do with 
it, and then it's a case of guilty until proven innnocent.....it sucks !

....and, ah, I'll get back in my box now ! :P

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