Topband: Matching Transformer

[Lee K7TJR]

    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