50 Ohm source at 1.85MHz Load to be matched is 23 - j813 Ohms I am trying to find required values for the source-side C, the shunt L, and the load-side C for a standard T-network as found in desktop tuners. Using most of the on-line calcs, like this one, I get negative values for the capacitors. What is going on??? I do not have SimSmith on this computer.
Thanks Dan, Using my wife's laptop computer. All I have here is bare-nekkid EzNec. That is probably why my friend cannot match his ladder-line fed, non-resonant, 425ft horizontal loop using his desktop tuner on 160m. That is a lot of loss in the tuner. I am going to add a coil in the loop wire to see if I can cancel some of that reactance before the tuner sees it. How far would I have to reduce the -j term so that an normal T-tuner with 25 to 30uH could handle it? Tnx.
Assuming a 25 uH coil in the tuner, you can get a 2:1 SWR(50) with a load of 23-j400. If you want 1.2:1 the load jx has to be around -305. At around -j280 you can get an almost perfect match. Of course, that all assumes the tuner acts like a modeled tuner, big assumption. If the coil Q is 100 a load of 23-j305 still loses ~32% of the input power. Dan, AC6LA
Simple L-network. From the 50-ohm end: shunt 46.15 ohm C followed by a series 837.9 ohm L to the Load. Component values at 1.85 MHz: C = 1864 pF, L = 72.1 uH. ----- BB
Goal is to fix the antenna so that it can be tuned with the existing tuner; not build a custom tuner... I take your point that an L-network will always "work", even when a T-network wont.
Then just add a series ~813 ohm (70 uH) L between the antenna and tuner. All the tuner then needs to do is transform 23 ohms to 50 ohms. ----- BB
