Alinco DJ-X11


The Alinco DJ-X11 has in my opinion a too broad bandwidth for AM demodulation. The selectivity is bad. In some cases you can listen a signal even if tuned +/-10kHz away from the center frequency. Because I am using this receiver mostly within the frequency range 0.05-30MHz, i wanted to change the bandwidth for AM.



Please note.
This mod is only for electronic experts with good knowledge in soldering very small smd parts. The mod will void the waranty and if it fails, it will be not working anymore, so you do it at your own risk!



Description:
For AM demodulation, the filter FL103 (CFWKA455KEFA-R0) with ~ 25 kHz 6dB BW is active, this is done by the diode switches D146 and D143. For SSB demodulation a second, narrower filter, FL104 (LTWC455I) with ~ 6kHz 6dB BW is added by the diode Switches D146 and D143. So for SSB both filters are activated.

Because the ssb filter is large enough for AM receiption, I have changed the circuit so, that also in AM mode both filters are active.

Results:

If done successfully, the selectivity is better, comaparble with other shortwave Receivers. I could not hear a difference in sound quality.

Signals 5kHz away: still present, depending on signal streght. From my point of view it is normal, because the 5kHz spacing is overlapping in the AM bands. 

Signals 10kHz away: nearly completely notched, except very strong signals.


Changes in the circuit:
I have removed the diode switch B146 and hardwired the connection to the filter FL104 and added a capacitor of 100nF betwewn the output of filter FL104 and the free input of the diode switch D143. See the schematic below.



Part of the DJ-X11 schematic:

Before opening:

You must remove the nuts from both potentiometers.

To Access the PCB described you must remove the top PCB. Before doing this, the mini connector righthanded of the display has to be removed! There is a chinese video on YouTube showing how to open it.

Detailed view of the added 100nF capacitor and the hardwired Connection replacing D146: