Re: Ferrite cores

Charles Darley
 

Hi All
 
And thank you for the reply ... I am all up for experimentation and the BRATS club in UK now has 5 set under construction some much slower than others as they have to buy the parts from pocket money as a 10 years is building one with his 14 year brother ....
 
With  the club behind me I shall try to do experiments on the various ferrites and report back to the group.
 
Have a look at these pages
 
and it will show how wrong I was in my interpretation of the other data source - as it depends how you are using the ferrite as to their frequency....
 
We are working from the Audio amplifier and Mic end towards the antenna !!!
 
Thanks again for the helpful comments and this has given insight into the further experimentation ...
 
Charles   G4VSZ

-----Original Message-----
From: Jim Strohm [mailto:jstrohm@...]
Sent: 22 July 2004 19:45
To: BITX20@...
Subject: Re: [BITX20] Ferrite cores (and a bit of a rant)


On Jul 22, 2004, at 1:33 PM, Charles wrote:

> BUT can anyone sugest and explanation for using several different
> ones when the T 50 - 2 is listed for frequencies 1 to 30MHz and I
> would have thought could be used at all location.

You should take a look at Amidon's (or other vendor's) specifications
for cores.  For a given composition, induction can be estimated from
the specs and then confirmed from the actual wound inductor.  My
limited experience suggests that the spec sheets are pretty good and
will provide an inductor that measures within 25% of predicted.

I have never had the tools to be able to sweep by frequency for
inductance, I've only been able to see "it works HERE."

For transformers, the suggested frequency range is important but it
should not be viewed as an absolute limit.  If you choose  a core
that's outside the "suggested" range, your coupling won't be as tight
but you'll still see SOME coupling.  Will it be enough?  Will the
driving stage be able to push enough power into the core so that the
secondary can deliver enough power to the next stage?

Only your experimentation will show for sure.

Obviously, for those of us who like first-pass success, it behooves us
to follow tested and proven designs, and to respect the manufacturer's
specified limits on parts.

Moving right along, let's talk about those tap washers !!


Folks, all this stuff IS experimental and all of us are wandering
around in the dark with just a few candles in the distance.  What we
discover, and more importantly, the knowledge we share with each other,
is what matters.  If you want a radio that "just works" I don't think
this is a place you should be -- there are commercial manufacturers for
that.  For my part, I want to say "I built it" -- and whether that
includes using somebody else's design to etch a PC board, or using
somebody else's resources to sort crystals and kit them up, I think
that's OK in "homebrew."

Even with all the resources provided here, we're still miles beyond the
outer limits of Heathkit and "I built it."

73

Jim N6OTQ


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