Re: LTSpice simulation of uBitx Power Amp
Have now uploaded version two of the simulation:toggle quoted messageShow quoted text
Has the following changes:
Quiescent drain current reduced to 10ma on both.
Added a switching mechanism to show response at both 7 and 30 mhz with a single run.
Power out on WA2EBY is still much lower at 30mhz than he reported in his QST article.
Input impedance at 30mhz falls to 12 ohms, which is the primary factor here.
If Vin source impedance is reduced from 50 ohms to 0 ohms, then 30mhz output exceeds 7mhz output.
Removing C3 increases output a bit at both 7 and 30mhz
L3 helps make the exciter see a resistive load, but doesn't help much.
I'm moving on to other things.
Let me know if anybody figures out why my model of the WA2EBY amp shows the output to be so much lower at 30mhz
Here's my notes on how I got the WA2EBY inductor values, includes a python script for single layer coils:
# Single layer coils, wheeler formula: Henrys = 0.001 * N**2* R**2 / (228R + 254L)
# where N is number of turns, R is radius in meters, L is length in meters (>0.8r)
def h(n, d, w): # turns, form diameter in inches, wire diameter in inches
length = w*n/39.37 # length of coil in meters, assuming close wound
radius = (d+w)/2/39.37 # radius of coil from middle of wire in meters
henries = 0.001 * n**2* radius**2 / (228*radius + 254*length)
L1, L2 9-1/2 turns #24 enameled wire, closely wound 0.25-in. ID >>> h(9.5, 0.25, 0.02): 5.285e-07 = 0.5285uH
L3 3-1/2 turns #24 enameled wire, closely wound 0.190-in. ID >>> h(3.5, 0.190, 0.02): 8.222e-08 = 0.0822uH
T1 10 bifilar turns #24 enameled wire on an FT-50-43 core uH=(AL*Turns**2)/1000 AL=440 (440*100)/1000 = 44uH/winding
T2 10 bifilar turns #22 enameled wire on two stacked FT-50-43 cores. AL doubles (880*100)/1000 = 88uH/winding
T3 Pri 2 turns, sec 3 turns #20 Tefloncovered wire on BN-43-3312 balun core. AL=7000 (7000*4)/1000=28uH, (7000*9)/1000=63uH
On Sun, Feb 4, 2018 at 10:21 pm, Jerry Gaffke wrote:
I've now uploaded an LTSpice simulation schematic file that allows easy comparison of the uBitx and WA2EBY finals,