----- Original Message -----
From: "Lee K7TJR" <k7tjr@msn.com>
To: <topband@contesting.com>
Sent: Saturday, June 30, 2012 9:54 PM
Subject: Topband: Laird ferrites
> Evaluate against what?
> Hmm seems kind of a silly statement to me as a designer.
Maybe you just dont understand the process.
> Evaluation is the job of component engineering in most companies. They
> make
> sure that the components conform to the specification data sheets provided
> or
> not by the suppliers. Just so you always purchase the same thing.
In a real company a project engineer searches data sheets for something that
looks good and then asks for samples. If the engineer has any experience he
already has preferred companies in mind and in the ferrites world there are
many. In many cases testing in the lab is minimal if the requirements arent
stringent. Even when strict parameters must be met the choices usually fall
to a company that has readily available data. IOW, if it fits the job then
use it and dont waste time chasing rainbows.
A component engineer is after the fact and is between R&D and production.
> There are 25 toroid transformers accomplishing various functions in
> my highly
> successful 8 element receiving array, not counting the 8 in the antenna
> elements..
> One cannot simply design a broad band transformer from a data sheet having
> lots or
> little information and expect it to accomplish perfectly its function.
> Each function is
> generally methodically tested to verify that the transformer does indeed
> perform its
> function with minor variation. One cannot assume that will happen just
> because the
> data sheet provides various parameters. About the only thing Fair Rite
> says about
> wideband transformers is to use High u and few turns. Hmmmm.
Many have already proven that a wide band transformer is a fairly simple
device and they have been around for over 50 years.
The key to performance then is in the winding and that takes some skill in
the process. For a Beverage transformer, primary to secondary isolation is
important if minimal common mode problems are critical, and improved
bandwidth is usually a side benefit that doesnt concern a single band device
such as an 8 square. Maybe isolation isnt that critical either.
> My point is this. Jim K9YC has measured cores and provided useful
> data for the
> masses. This is wonderful but it did not come from any companies data
> sheet. Jim
> has pointed out what you need to duplicate his efforts. I find no reason
> to throw the
> baby out with the bath water. Who is to say the Laird ferrites might not
> work even
> better in a K9YC evaluation. Most successful amateur applications of
> ferrites do
> not come as a result of the manufacturers data sheet but as a result of
> some tests
> done by someone in the past.
> By thorough evaluation in my circuits, I have found an off brand ferrite
> to perform
> well beyond my expectations. They were not chosen because of price. They
> were
> also not chosen by what it says on the spec sheet.
> Lee K7TJR OR
Ive been involved with ferrites at the R&D level since the early 80's and
have related some of those results on here many times.
Anyone familiar with the Tempest program knows that extreme levels of EMI
suppression, cable issues and the like go back into the 70's.
While Jims pages are fine for EMI that doesnt mean they are valid for
transformers.
ON4UN's book is minimally useful since his sources dont reveal the details
and appear to deliberately have misleading statements at times. Probably to
protect their commercial endeavors.
Carl
KM1H
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