Rick,
Thanks for the brief review of MiniCircuits stuff (I'm not connected with
them in any way except as a customer).
Since you've characterized some of their parts, perhaps you could help
answer a question that someone else posted, and one that I would like to
have answered as well.
Have you measured the effects of DC current in the windings of an RF
transformer, such as is seen if the transformer is in the collector circuit
of an amplifier? If so, could you provide a generalization of the effects,
such as changes in frequency response, losses, etc.?
Many Thanks!,
Dave M
Richard (Rick) Karlquist wrote:
On 11/27/2014 7:07 AM, Tim Shoppa wrote:
For a hobbyist doing things a few at a time, what advantage is there
to buying RF transformers made by Mini-circuits etc., vs winding
them using commonly available ferrite cores/binocular cores?
If I needed to do a production run of 1000+ boards with tiny SMT
transformers, sure, no problem buying them from mini-circuits or a
distributor etc. But for hobbyist stuff seems far more flexible to
wind them onesy-twosy using not so tiny cores and windings selected
for the particular application.
Tim N3QE
You need the tiny cores to get the performance of the MiniCircuits
transformers. You just can't get the same bandwidth using macro sized
"binocular" cores. Now, if you don't need a lot of bandwidth, then
what you are saying could make sense. Another issue is stray
capacitance. Considerably lower with a tiny core.
I have spent many hours characterizing MiniCircuits transformers
beyond the data sheet specs, and dissecting them to learn how they
do it. They really do have a lot of rocket science in them. In
terms of the engineering I am buying (especially in a one-off
application) they are ridiculously cheap. And I say that as a fairly
knowledgeable transformer designer in my own right.
I do keep binocular cores around for higher power transformers, and
for "emergencies" when I need a transformer "yesterday".
Rick Karlquist N6RK
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