Sweep output debugging [2 Attachments]

Steven Dick

I would first get two lengths of different colored wire.  Then take the middle of one wire and make a small loop in it about an inch long.  You can twist the loop itself a bit to keep it in a loop. Then put the two wires together and twist them together.  Wind a single turn through the toroid at the middle of the wire pair with the loop at the center sticking out. Then complete winding 6 turns around each side of the middle giving you the required 12 turns. Make sure the 6 turns on each side of the “loop” are wound in the same direction. I.E. of the loop wasn’t there, you would wind 12 turns of twisted pair.  Then tie the loop to ground. The loop becomes center tap of the bifilar wound transformer.
Regards, “Digital Steve”, K1RF

Sent: Friday, February 19, 2016 3:19 PM
Subject: [PHSNA] Re: Sweep output debugging [2 Attachments]

Some debug done, I terminated the output with 50Ohm and connected a BNC cable to RF detector with clips in the other end and measured my way back by sweeping with PHSNA.exe and found that is already after T1 I have the dip in the signal.

Steve, you might have been spot on from the start :-). I'll try the bifilar winding but how would I do the center tap which I assume that I should ground? Do I wind 12 bifilar turns and then just cut the primary winding in the middle and ground it?

Marcus, SA5PMG

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Steven Dick

Just to be clearer, there should be an equal number of turns around the center tap so push-pull operation is balanced.  So there really needs to be a total of 11 turns or 13 turns. One at the center and 5 or 6 on each side of the center turn. 5 better if you want to have the best high frequency response, 6 is better is you want best low end response.