[AMRadio] Part 15 Devices


jeremy-ca km1h at jeremy.mv.com
Sun Dec 2 16:52:06 EST 2007


Beads over antenna cables and line cords only blocks common mode signals. RF 
can still flow thru line cords and into the house wiring or thru the coax 
into other equipment.

Many years ago Doug DeMaw had a QST article on a brute force line filter 
that actually works well. Ive built several inside outlet strips and plug 
all sorts of offending equipment into them.

I also use ferrite beads but not the snap on type which are 43 mix and 
fairly useless at low frequencies. A mixture of 77 and 43 mix beads that 
just slip over RG-6 work best for me followed by a good HPF on TV's, VCR's, 
DVD's etc.
Line cords get wrapped on a 33 mix ferrite rod or you can use a 77 mix 
FT-240 size toroid.

If the TV is radiating through a plastic cabinet you can line the inside 
with aluminum foil or spray on a conductive coating.

Since I operate from 1.8 MHz thru 10 GHz I sorta got obsessive about RFI in 
both directions. It takes some time, effort and money to do it all.

Carl
KM1H


----- Original Message ----- 
From: "Jim Wilhite" <w5jo at brightok.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Sunday, December 02, 2007 4:12 PM
Subject: Re: [AMRadio] Part 15 Devices


> Yea I have read it Bob.  And given the attitude of the FCC I really don't 
> think they would take any action.  The first answer is always, "Move 
> something".  I sure would like the FCC to get back into non-interference 
> and enforcement.
>
> Jim/W5JO
>
>
>
>
>
>>I have haerd that the new flat screen TVs are the worst offeners. The 
>>FCC's
>> solution is to have the owner of the device stop using it.
>>
>> Have you tried reading Part 15?
>>
>> Bob Macklin
>> K5MYJ
>> Seattle, Wa,
>> "Real Radios Glow in the Dark"
>> ----- Original Message ----- 
>> From: "Jim Wilhite" <w5jo at brightok.net>
>> To: "Discussion of AM Radio in the Amateur Service"
>> <amradio at mailman.qth.net>
>> Sent: Sunday, December 02, 2007 12:35 PM
>> Subject: Re: [AMRadio] Part 15 Devices
>>
>>
>>> Well guys I put snap beads around the power cord (about 6 of them as I
>>> recall) and still hear it on several frequencies in the 75 meter band.
>>> It radiates as much as 50 ft. away and I don't think they should have
>>> that much.
>>>
>>> On top of that, the frequencies move when the state changes from off to
>>> on.  Like all of you my house if full of these devices.  My HP computer
>>> doesn't do this, my Canon multi-purpose printer doesn't do this, none of
>>> the kitchen appliances do it, the DVD player doesn't and neither does my
>>> electronic thermostat.  All of which I can take a portable receiver and
>>> go near and hear them on the same frequencies with the TV unplugged.
>>>
>>> One leg of my 75 meter antenna is about 50 ft. away and the TV causes
>>> spurs that can be heard that far away.  I know it isn't the satellite
>>> box and not the answering machine adjacent to it.  Everything clears
>>> when I unplug the TV.  It is the first TV I have ever had that radiates
>>> this much.
>>>
>>> Jim/W5JO
>>>
>>>
>>>
>>>
>>> > How do you know it is out of compliance? There are measured radiation
>>> > limits. Every one of the new entertainment devises that has a remote
>>> > controller have a microprocessor that runs all the time unless the
>>> > device is
>>> > unpluged. You can get radiation off the cables. unplug all the cables
>>> > and
>>> > see what you get.
>>>
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