Hi all
I have launched a single?band version of QDX called QDX-M. The 'M' is for monoband. The kit price (and assembly fee if you choose that option) is slightly?less than the price of the? normal multi-band QDX. This reflects the (disappointingly) slight decrease in production costs. Price: $65 (assembly option: $40).
QDX-M uses the same firmware as QDX, the only hardware difference is that all band-switching components have been deleted. This simplifies the construction but of course makes it mono-band.?
So far in testing the 10/11/12m version of the kit I have found that there is a noticeable improvement in Receive performance. Though the high-bands multi-band QDX also has sufficient sensitivity on 10m, the sensitivity does seem to gain several dB on the mono-band QDX version. This is not unexpected, since the signal no longer has to pass through band-switching multiplexers, and the board layout is simplified resulting in less stray/parasitic inductance and capacitance.?
The main motivation for this version was to be able to provide QDX operation?on 160m, 630m and 2200m. On these bands, the operating frequency is too low for the PIN diode switching to work properly. So a single-band version of QDX is necessary for these bands. The board has lower density which means we can use larger toroids for the LF bands to fit the necessary number of turns for the higher inductance.?
I will be working on production of the LF versions over the next week or two. Eventually I aim to provide a single-band version for any band from 2200m to 10m.?
Initially I only have 10, 11 and 12m versions available. These are in fact all the SAME version, and so this version will work on 3 bands :-)? the only difference, when configured, is the position of the vertical band indicator line on the RF sweep screen in the terminal configuration utilities.?
The QDX-M firmware displays only a single entry in the Band Configuration screen. The single entry is configured automatically by the firmware for the band you choose to build the kit for, controlled by your choice of jumper wires (install following the instructions in the assembly manual).?
