Hello friends,

I have a QDX which works here in WSPR mode and does an excellent job.
My model makes the bands from 80 - 20m. Now I have read that you can also equip the bands differently. I am now interested in the QMX. On the one hand it should provide the missing bands for WSPR operation, on the other hand it should also be used for (rare) CW-QRP operation.
Now my question: Is it possible to build a QMX with the bands 2200 - 630 - 160 - 17 and 15m? It is only about the technical feasibility, that there might be problems with the space for the filter cores is clear to me.

73 Joe

HelloJpe,

The short answer is no; you can not switch multiband LPF with the diodes used in the QDX or QMX LPF selection.? The carrier persistence is not there for the lower frequencies.? This was one of the reasons for the single band QDX, as only one LPF is used with the switching diodes removed.? So far, I have seen 80 meters as the lowest for a multiband QDX.? Currently, there is only the 80 - 20 meter QMX offered.? You can mix and match any bands from 80 to 10 if you change the bandpass and low pass filters to match.

With the above understanding, it should be possible to build an external relay switched LPF assembly and change the BPF components to match as that is a MOSFET switched IC for selection.? For LPF selection, you are limited to only three possible.? This means to get more than three bands; you would need to share LPF for two or more bands.? Not feasible for the lower bands.

The above is my understanding at this point.? Others may have better information than I do.
73
Evan
AC9TU

On 16/09/2023 07:51, df2jp_1 wrote:

On the one hand it should provide the missing bands for WSPR operation,

Joe,

For WSPR I do not expect the QDM to be any different.
With latest firmware a QDX may be setup on any bands but there will only be 3 LPFs.
Low frequencies will not work unless you remove the switching diodes and make it single band. External filters could be used to use it on more than one band.

73 Alan G4ZFQ

On 16/09/2023 08:18, Alan G4ZFQ via groups.io wrote:

External filters could be used to use it on more than one band.

I should add that I have a QDX5M.
I have fitted sockets and can plug in different filters.
I had thought of using it for LF although it is on 20m at the moment.
My method is crude but someone might do it a lot better.

73 Alan G4ZFQ

Sorry, Joe,? I did not see the typo in your name in my prior post.

73
Evan
AC9TU

开云体育

Hello Joe