Thanks for the tip about power measurement. I was not aware of either ALT-Right or CTRL-Left clicks.
I did no see much difference between conventional and WTST myself.
Tony
AD0VC
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Tony,
You can clearly see the improvement in coupling that the twisted winding has over the conventional winding, with the expected improvement in leakage inductance as well.
I think that is especially significant at 10m since the leakage inductance has probably not been factored in to the LPF design, and at 10m is approaching the size of the filter inductors.
The negative inductance you see is the parasitic capacitance overwhelming the inductance ie. a resonance. It makes extracting model parameters more challenging.
I run with a variant of the twisted pair transformer in my QDX-HB. It is a 12V 3:2 design . The twisted pair is fully the length of the longer wire. The ratio is obtained by tapping points on the secondary, leaving wire ends to dangle. This
technically more fully realizes the transmission line properties of the twisted pair approach, although I am hard pressed to see much of a performance difference.
JZ
FWIW here is what I measured for the conventional and WTST using my nanovna. I verified the calibration when I saw the negative inductance for the WTST at 28Mhz.?
Conventional????????????????????????
??????L Wind (uh)?L Half Wind?Leak??K
7Mhz??13.56?? ? ? 3.92??? ? ? 0.107?0.996046758211066
10Mhz?10.42?? ? ? 2.98?? ? ? ?0.107?0.994852394070841
14Mhz?7.42??? ? ? 2.13?? ? ? ?0.106?0.992831448793946
18Mhz?5.2???? ? ? 1.51??? ? ? 0.106?0.989755214492647
21Mhz?3.6???? ? ? 1.16??? ? ? 0.106?0.985167780408777
28Mhz?1.26??? ? ? 0.435?? ? ? 0.106?0.957012547395809
????????????????????????
WTST????????????????????
7Mhz??12.98?? ? ? 3.72?? ? ? ?0.067?0.997415767187798
10Mhz?10.13?? ? ? 2.91?? ? ? ?0.067?0.996687504803284
14Mhz?6.97??? ? ? 2.05?? ? ? ?0.066?0.99525416175213
18Mhz?4.11?? ? ? ?1.28?? ? ? ?0.066?0.991938307476537
21Mhz?1.96??? ? ? 0.74??? ? ? 0.066?0.98301908964793
28Mhz?-1.43?? ? ?-0.18?? ? ? ?0.066?0.976650476806393
Tony
AD0VC
Tony,?
In LTSpice if you hover the cursor over a component as if to measure current through it, then press ALT and right click, LTSpice will give you a plot of instantaneous power. You can window that plot for the time period of interest. Then hover
the cursor over the plotted variable name above the plot. Press CTRL and left click. LTSpice will integrate the instantaneous lower over the window interval and open a box with the result.
Since core magnetic materials tend to show reduced permeability at increasing frequency, I like to use my NanoVNA to measure inductance as seen at the relevant frequency. This usually works pretty well unless parasitic capacitances bring a resonance
nearby.
JZ
John,
A couple of things. First, how are you getting the mosfet dissipation from the spice simulation? Are you eyeballing an instantaneous power (Vd * Id) waveform and doing a mental average??
Second, I just built a conventional 9 volt transformer and a WTST transformer and measured the leakage inductance and inter-winding capacitance. Two different cores of course. Measured at 100Khz which is as high as my LCR meter goes.
Conventional:
L winding = 25.5uh
L half winding = 7.65uh
Lleak = .505uh
Cps = 7pf
K = sqrt(1-(.505/25.5)) = .99
WTST:
L winding = 27.6uh
L Half winding = 8.12uh
Lleak = .515uh
Cps = 11.3pf
K = sqrt(1-(.515/27.6)) = .9906
Useful for the SPICE model.
For those that care about this nerd stuff.
Tony
AD0VC
Sure thing, Chris.
Simulation at 25 ohms (2:1 SWR) shows each BS170 dissipating about
half a watt, so there is some margin.
JZ
On Thu, Sep 14, 2023 at 9:26?AM Chris KB1NLW via
<chrisrey1=
[email protected]> wrote:
>
> John Z
> Thanks for your response. Looks like steady state SWR of 3 will heat the BS170s to their PD limit, so I assume SWR <2 is OK.
>
> Transients from an auto tuner that can be as high as SWR of 10 will cause transient power dissipation significantly higher than the allowable dissipation.? Unfortunately we don't have sufficient thermal data on the BS170 to understand transient thermal response
at the silicon chip in order to determine allowable SWR Transient time product.
>
> Bottom line is Don't Use an Auto Tuner without reducing the transient at the QMX.? Reduced power or attenuation between QMX and tuner.
>
