Re: New QMX Rev3 build - no power out...
|
Michael, one more thing... The RWTST transformation ratio may be a little different than what the above calculation indicates. No problem.
The issue is that it is a rather unconventional design which brings together properties of a transmission line transformer (the twisted pair segment) and properties of a conventional transformer (the no-twist segment).
The calculated value above should not be too far off, though, since RWTST clearly functions well in circuit.?
JZ
Michael,
Yes, a sweep of 14MHz to 30MHz is correct.
IIRC you are using the 12V RWTST transformer. The full primary has 3 turns, the secondary has 2 turns.
The turns ratio (3:2) or (1.5:1) produces a?? 1.5 x 1.5 = 2.25 impedance ratio.
With the Nano connected to the full orimary and the load resistance on the secondary, the NanoVNA will see 50 x 2.25 = 112.5 ohms.
Put into SWR mode, with all other traces turned off, you will see a nominal SWR reading of 2.25. The reading will vary somewhat over the sweep range as the transformer frequency response rolls off at low and high ends of the sweep.
You can also do this in reverse. If you place 112.5 ohms at the full primary and the Nano on the secondary, the Nano will see 50 ohms and show SWR = 1.
Hope that helps ... JZ On Wed, Mar 27, 2024, 7:50?PM Michael LaBlanc < mlablan1@...> wrote: John,
I have T501 rewired and have some test leads connecting a 50 ohm load to the secondary windings and my Nano VNA attached to the primary windings.? I am not sure which trace will give me the transformed?impedance?? Is it the resistance value?? I have attached some pics to show what choices I have to select measurement types.? Also, what frequency range should I put in for the stimulus?? Since this is a 20M to 10M radio, should I put in 14MHZ to 30MHZ?
Thank you again for all this assistance.? Knowing if this transformer is properly wound before I insert it on the board will be a huge advantage.
  
|
