RadioBanter - View Single Post

July 24th 05, 02:24 AM

In article .com,
wrote:

Telamon wrote:

That depends on the core. Some are no good for 3 to 30 MHz.
TV operates at 50MHz.

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Telamon
Ventura, California
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So people keeep telling me.
I have built many, around 30,of these little gems and they all
worked down to below MW with minimal losses. Read Mr Doty's
comments. They have all worked great from .5MHz to above
20MHz with every scalvaged TV core I have used. Perhaps I
have just been lucky, or maybe, just maybe for cores so small
loss are not as high as many people think.
I will include an observation from Mr Doty himself:"

Snip

Well then how many times am I going to have to tell you then is the
only question left.

All cores have a frequency response range. You have to pick an
appropriate one depending on where you intend it to operate. I have
come across ferrite cores that are worthless 10 MHz so it may work
well on the upper bands and poorly on the lower. You may not notice
this right off because evening and nigh time signals on the lower bands
generally have more signal power.

I believe you have some basic equipment so you can check it out.

I think you may have better luck in the power supply section of
equipment you are tearing apart for components. Specifically the EMI
section will likely have some common mode chokes that are designed to
operate over the short wave spectrum to suppress conductive noise.

TV RF ferrites are designed for 50MHz to 500MHz or something along those
lines and their response of some falls off on the low end so I don't
recommend using them unless you can test them.

You either need to know that the material is of a certain type or be
able to test it.

--
Telamon
Ventura, California