When will my kit be sent, when will it arrive, etc etc.?
Will I get the latest firmware version when my kit ships?
Is there a mailing list for the QCX kit?
What technical support is available?
Is an enclosure available or planned for the QCX kit?
What are the dimensions of the PCB?
Are other bands possible?
Is a multi-band QCX possible?
Why do I have an MPS2907 transistor in my kit, but no MPS751?
After the initial launch of the kit on 21-Aug-2017 a very large number of orders were placed within 24 hours. Over 300 kits were sold in the first 24 hours. It will take some time for the shipment office part-time staff to cope with this massive order volume. They will do their best. Please be patient. You have been assigned a Serial Number, and you can see which Serial Numbers have been shipped on the main QCX page. The page will be updated daily. The shipment office staff do not ship packages every day so you will not necessarily see a change in the Serial Number every day. Eventually when things return to normal, we should aim to get back to the usual 3 business days target (from order placement to shipment).
For other questions regarding shipping, please refer to the main FAQ page.
Yes! All kits always use the latest firmware version available at the date/time of shipping.
If you think you need technical support, the following options are available - in order of preference: I mean, the first one in the list is to be done first! Do NOT start with 3...
- The vast majority of problems or questions are already answered by information in the documentation! The old adage "RTFM" generally applies. Are you sure you read the documentation thoroughly? Check again - also check elsewhere on this FAQ page and on the QCX kit page to see if the information you need is written there.
- Ask on the QRP Labs distribution list https://groups.io/g/QRPLabs. Not a member? You should be! Please join us!
- Email QRP Labs, CLICK HERE for details. We can decide how best to answer your question - by email, telephone, Skype, etc. In the very last resort you can send us the kit and we'll get it working for you (free of charge) and return it.
We do not have an enclosure available for the QCX CW transceiver kit. We do not have any immediate firm plans to supply an enclosure, but it may be something we investigate in the future.
The PCB size is 4.0 x 3.2 inches (101.6mm x 81.3mm). The 3.5mm jack connectors protrude on the left and right sides, and the BNC connector is the largest item sticking out on the right side at the rear (please refer to the diagrams in the manual). When the LCD module is plugged in, the top (front face) of the LCD is about 20.5mm above the surface of the PCB. The 12mm hex spacers on the lower side, plus the PCB thickness, bring the total thickness to 34mm. The two knobs stick out above this.
The transceiver should work on 10, 12 and 15m bands and kit versions for these bands may be made available in future, once we have had time to test operation and performance on these bands.
The transceiver as it stands, cannot work on 160m or LF bands. The reason for this is that the Si5351A Synthesiser chip can only produce a quadrature output (90-degree phase difference) on two of its outputs, down to a minimum frequency of 3.2MHz. Therefore the system can work for 80m (3.5MHz), but not for 160m (1.8MHz) band and below. Modifications would be required to generate the quadrature LO, probably involving a divide-by-4 circuit (e.g. with 74HC74 chip).
There are three circuits in the QCX which have band-dependent components:
- Low Pass Filter (LPF) which is for transmitter output harmonic filtering (inductors L1, L2, L3 and associated capacitors).
- Band Pass Filter (BPF) which filters unwanted signals and prevents them reaching the receiver input mixer (transformer T1, long secondary winding and capacitors).
- Class-E Power Amplifier resonant circuit (L4 and associated capacitor).
The assembly manual provides tables of component values per band, for each of these circuit blocks. Changing the band requires changing all three circuit blocks. In a multi-band QCX you would need to arrange switching between copies of these circuits, one copy per band. It is not impossible. But neither is it trivial...
The first 500 kits manufactured used the MPS2907 PNP transistor for key shaping. Some constructors reported that the transistor burnt out. It has a 600mA current rating. For the subsequent kit batches, the MPS751 transistor was used instead. The MPS751 is a PNP transistor with the same pinout as the MPS2907 but 2A current rating. So you should use the MPS751 for Q6, if the MPS751 is supplied instead of MPS2907 in your kit. The assembly manual does now refer to the MPS751, but you may have an older version of the assembly manual; or there may be some references still to the MPS2907.
Actually, the 600mA rating of the MPS2907 should never have been exceeded anyway. But some people reported a power amplifier instability problem, seemingly possible on 17m and 20m versions; I think that this is what caused the current to exceed 600mA and kill the MPS2907 in some cases. You can see a modification that resolves the power amplifier instability problem here: http://qrp-labs.com/qcx/qcxmods.html#pa . This simple modification involves adding a 10K resistor. It is recommended to carry out this modification even if you are using the MPS751. A spare 10K resistor is supplied in the kit from serial number 1500 and above.