Fixing a problem with HF reception on a chinese RTL SDR

I recently bought one of these little SDR boxes from a chinese vendor on the web. It was expected to allow reception of both VHF/UHF frequencies and HF frequencies.

Internally, the unit contains a small PCB from a typical RTL SDR dongle (built around the RT820T + RTL2832U chipset), mounted on a larger PCB and connected to it by means of few solder joints (on the back side of the larger PCB).
The larger PCB also hosts two SMA antenna connectors (labeled "UV" and "HF" on the aluminium enclosure), the USB connector for communicating with the PC (which runs the SDR sofware, typically the SDR# application) and a "power on" blue LED.
The "RTL SDR dongle" part of the unit is in charge of managing signals coming from the "UV" antenna connector (a SMA female port), just like on any typical USB-pluggable RTL SDR unit.

On the remaining area of the larger PCB, the "HF" antenna input is connected to a LPF filter followed by a single transistor stage, which purpose is to take the HF single-ended signal from the LPF filter and to translate it into a double-ended signal for the RTL2832U chip ("Q" port of the internal ADC, pins 4 and 5).

The RTL2832U must be configured for "direct sampling" mode of its "Q" input, to properly manage the HF signals received on its pins 4 and 5. This can be made by means of the SDR software application running on the PC (for example, the SDR# application).

That said, after having connected the unit and properly configured it on SDR#, I had to discover it didn't work on HF. After some investigation, I found that the transistor at the end of the HF branch (which is mainly in charge of generating a double-ended signal for the RTL2832 pins 4 and 5) did not show any voltage on the collector terminal.
I connected it to the 3,3V output from the voltage regulator on the RTL dongle PCB and things got better. Following photographs show the wiring from the AMS1117 voltage regulator (which takes the nominal 5V level from the USB port and produce a 3,3V level for the on-board devices) to the collector load resistor of the transistor (look at the blue arrow on photograph below).

You will also notice (in a yellow circle) a non-SMD ceramic capacitor (10 nF) that I have had to solder in place of a SMD capacitor that unfortunately I had broken during initial tests.