On 10/29/2010 8:52 AM, tzikas tzik wrote:
> Hi, i have a transmitter 500w. I am using coaxial audio cable to give
> modulation to the pll. I have many problems with R.F interferences from my
> antenna or linear to pll. I believe that the audio cable collects R.F from
> the antenna and transfers it to pll. I have read some articles about this
> problem. the last one is this:
> http://www.audiosystemsgroup.com/SAC0305Ferrites.pdf
> I have read this:
>
> <<*Avoid the use of shielded cables with a drain wire if the system will be
> exposed to
> strong RF below 10 MHz (AM broadcast, ham transmitters, light dimmers). Any
> cable
> with a drain wire will have significantly greater SCIN below about 10 MHz
> than
> a cable that uses a good braid shield. On the other hand, foil-shielded
> cables provide
> better shielding above 20 MHz. The best cable, if you can find it, is one
> that
> has both a foil and braid shield. Second best are those with very dense
> braid
> shields.
> Both of these cable mechanisms are quite powerful -- simply switching from
> zip
> cord to twisted pair for loudspeaker wiring, or from foil/drain cable to a
> good braid
> cable, can easily reduce RFI by 20-30 dB if that is how the RF is getting
> in.>>
>
> *I can't understand it very well (my english are not very good). The editor
> says to use or not coaxial cables for audio? What do you propose? *I*f i
> must not use coaxial audio cable for modulation , what cable is most proper
> to use for this purpose, to avoid R.F interference to my pll?
> Thank you very much!
I wrote those words, so I will try to help say it better. I'm sorry that
my words are not clear enough. The words you are reading are written
about audio cables with two wires inside the shield. Some cables are
built with aluminum foil and a copper wire as the shield. This wire is
called a "drain" wire, and it causes RFI problems. The best shield is a
dense copper braid.
You have also used words I don't understand, so I don't know how to
answer your question. What is pll?
73, Jim K9YC
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