Bob said " The ferrite donut I used to make the transformer was FT-114-43,
today I just read where I really should have used the 75 instead of the 43
mix."
First off, I do not think there are any manufacturers of 114 size toroids
available
in 75 mix. Only smaller sizes.
In addition here are some things that show you are OK with your
transformer.
Most importantly to you is that different materials provide different
permeability.
This means there will be a different amount of inductance in the same number of
turns on different material cores of the same size.
Choosing the FT114-43 shows an initial permeability "Al" of 510 nh per
turn
in the spec sheets. You have used 10 turns and in order to find the inductance
of
the primary you use L= Al*N^2. Using your 10 turns causes 100 times Al. this
is
51000 nh (Nanohenries) or 51 uh (Microhenries). We need to know this because
when designing a transformer a rule of thumb is to use a primary winding
inductive
reactance at the operating frequency that is at least 5 to10 times the expected
operating impedance.
In your case I assume you are using 75 ohms on the 10 turn side. Using the
lowest
operating frequency of 1.8MHz "F" the reactance is XL=2*pi*F*L or
2*3.14*1800000*.000051 = 577 ohms. While not 10 times the 75 ohms, it is not
that bad and I suspect you would not be able to hear or measure any difference.
Interestingly enough if you were using 50 ohm coax it would be over the ten
times.
Opinion, Drive on Bob you got worse things to worry about, If you are hearing
noise
and signals, your transformer is fine.
Lee K7TJR OR
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