I am pleased to announce the availability of the 60-15m QMX version, which has been requested multiple times by POTA and SOTA operators.
Note that there will be a few days' delay; the Rev 4 QMX boards will allegedly arrive here today according to the cargo company contracted locally by FedEx. But there will be some work to pack kits and program bootloader etc. I will also prepare a Rev 4 assembly manual update which will include the assembly instructions for the 60-15m version.
This version uses the 60/40m and 30/20m LPF designs from the 80-20m QMX, and the 17/15m LPF design from the 20-10m version of the QMX. All toroids are T30-17 (same as in the 20-10m QMX). The power output is normal on all 6 bands and the harmonic content has been tested and found to be excellent too; on 60m I measured -47dBc 2nd harmonic and -57dBc 3rd harmonic. On all other bands all harmonics were better than -60dBc.
The legendary Texas Instruments LM4562 op-amp is unavailable. I had to change the op-amp. I refuse to accept any reduction in performance. The only op-amp I know of which can meet the performance of the LM4562 is the LT6231 chip made by Analog Devices. Therefore the QMX Rev 4 PCB uses this LT6231 op-amp. I'm not talking about some re-badged clone merely claiming to be an LT6231 which is (probably) used in some transceivers, which anyway don't have the performance elsewhere for it to matter; I'm talking about the real deal which I purchased via Mouser US. The LT6231 is in my view the absolute KING of Op-amps but is a little pricey.
Due to the change to the LT6231 op-amp which is considerably more expensive than the LM4562 (and two are needed in a QMX), and due to certain other price increases, for this batch of QMX the component and manufacturing price increased by $7.47 per QMX. Accordingly I have had to increase the price from $95 to $102.47.
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