The usual rule with broadband RF transformers is at least 3-5 times more than the load impedance at the lowest frequency of interest. In this case for a 50 Ohm system more than 250 Ohms (10.6 uH at 3.68 MHz), so 400 (or 17.3 uH) would be fine.
For the FT23-43's I was using that is at least 8-9 turns. My transformers did not have that many turns, but still worked fairly well. (They had 7 turns which is ~7.8 uH or 180 Ohms which scrapes though in the 3-5 times rule of thumb.)
Regards,
Alan
5th January 2009 14:56
Anthony Sotillet wrote ...
Hi Alan. I'm writting you from Venezuela. Let me ask you a little thing. What should be the reactance of a DBM transformer? 400 ohm? or 200 ohm?
6th January 2009 06:00
Alan Yates wrote...
Anthony,
The usual rule with broadband RF transformers is at least 3-5 times more than the load impedance at the lowest frequency of interest. In this case for a 50 Ohm system more than 250 Ohms (10.6 uH at 3.68 MHz), so 400 (or 17.3 uH) would be fine.
For the FT23-43's I was using that is at least 8-9 turns. My transformers did not have that many turns, but still worked fairly well. (They had 7 turns which is ~7.8 uH or 180 Ohms which scrapes though in the 3-5 times rule of thumb.)
Regards,
Alan