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Hello,

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80-20m is my first QMX Kit, QMX+ (160-6m) my second, now I purchased a 20-10m QMX Kit.

I am using the QMX+ stationary, the smallones I want to use in portable operation.

80-20 and 20-10 means:? 2x 20 m and no 6m band.
The idea is to modify the 20-10m to 17-6m.
The first thing I do is studying the schematics and creating simulations with the original L and in ngspice to get a feeling.

If you are interested, here are the files:

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vy 73 Peter DL4PJ

Peter,?

Good idea! I think you have a winning idea.?

Altho the 60-15 m version is the sweet spot for me.?

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73, Dan? NM3A

Hello,

I uploaded the charts of the simulation to

The simulation now creates all charts at once and is easily customizable.

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Now I can start with my experiments to modify the QMX20-10 to QMX17-6

I am aware of the fact that this simulation is not reality. But they give me the direction.

My first impressions:

- The BPFs are very broad?

- The 10m BPF could also work on 6m

- Very experimental: using the 15/17m LPF for 20m

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Vy 73 Peter?

Today I soldered the original BPF configuration into my QMX 20-10.
Preliminary I bypassed the 20m LPF, and I left out the two other LPFs.

I configured all bands to use the LPF bypass and can sweep through the BPFs through all bands.

Everything works fine as I am used from the QMXs, but not as simulated ;-)

The band pass filter is much steeper than my simulation!

=> My assumption is wrong: I can't use the 10m BPF for 6m.

Maybe my configuration for the simulation is wrong?
- Did I use the right impedance (50 Ohm)?

- Is my circuit for the simulation correct??

I understand the BPF like this:

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RX IN ------ L ------ C ------- OUT

GND ---------------------------- GND

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Is this too simplistic? Is T401 to be seen as essential part of the BPF?

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73 Peter DL4PJ

Hi Peter,

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Here is an LTSpice XVII simulation for the QDX High-Band filters. I've included a PDF printout in case you don't have LTSpice.

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73

Evan

AC9TU

Peter,?

I recall some discussion about this in QDXs maybe in the past...and some thought that the impedance is NOT 50 ohms, and/or, not acting like it on that input.......?

Keep us posted with what you are able to do.... I've figured out that one could cover all bands 160-6 with the 6 band setup screen as far as generating the signals.... but the filtering for BPF and LPF would require a whole separate set of filter boards....And thus the QMX+ :-)

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-Nate?

N8BTR

Thanks Evan and Nate!

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I found the threads and an answer of Hans in an older conversation:

My Bpf simulation is too simplistic.

Impedance and the environment have a big influence.

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73 Peter DL4PJ?