ZL2PD's  KN-Q7 40m QRP SSB Transceiver

This new 10W PEP kitset transceiver features a tidy single-board design and fits in a compact aluminium case.

Introduction

The KN-Q7 is a low power (QRP) transceiver kit designed in China by amateur radio operator BA6BF. Here in New Zealand, we've been one of the first places to receive this kit. It's supplied locally by FutureTech. Having built the kit, I felt there were a number of areas in which the kit instructions could be improved. I noted down all the areas where I had a few problems, and documented it all. In addition, I think there are lots of possibilities to enhance the design. Things like an antenna tuner, an SWR meter, a power supply, additional bands, wider range VFO. The list goes on!

For the moment at least, this page includes: 1. My set of instructions on how to build this kitset, including hints on some tricky areas 2. A corrected schematic 3. Some pictures of my build (Maybe there's something in these that will help the next person...), and 4. Some specifications on some of key components used in the KN-Q7 transceiver Disclaimer: I have no association whatsoever with either FutureTech or BA6BF

This compact VCXO-tuned kitset transceiver designed by Chinese amateur BA6BF operates on the 40m band and delivers up to 10W PEP. I used a 4-pin microphone connector, shown here in this front panel view, to match my Icom HM7 microphone. An 8-pin socket is supplied in the kit.

Why New Instructions?

Over to the right of this page, you can click and download  a new set of instructions on how to build the KN-Q7 transceiver kitset. Why did I create a new set of instructions? Doesn't the kit contain these? Well, yes. The kitset does include some instructions. It's just there are quite a few little details that are not included. There were a few errors in a couple of places, and the schematic was a little difficult to follow...  So, while the transceiver kit is quite straightforward to build for experienced builders, these instructions are intended to make the task easier for the rest of us. And besides, why repeat my mistakes? These new instructions also follows my preferred method of construction -- One stage at a time. Building the transceiver section by section, and testing each section as soon as you've completed it, allows any faults to be located more quickly. A fault is probably somewhere in that last set of parts you just added. Now, this is in stark contrast to the instructions provided with the kit. It suggest the opposite approach i.e. Build everything all in one go, and then test it. Well, fine. Personally, I find that is not the best approach. A fault can be very tough to find when you’ve got an entire board of parts and connections to check! Anyway, I followed my step-by-step approach, and it worked. It also allowed me to break up the construction into a bunch of easy stages, with breaks well-timed for coffee. But, hey, it's your kit, right? You choose!

These instructions allow you to build the kit in the following stages: 1. Parts Inspection and Sorting 2. Surface Mount Devices - 3 chips to be soldered onto the PCB first 3. 8VDC regulator and rear panel sockets (Speaker and DC input) 4. Receiver audio 5. Second Mixer and BFO -  Doubles as the transmit microphone amplifier and carrier oscillator 6. Transmit-Receive Power Supply Switching 7. Receiver IF Amplifier 8. IF Crystal Filter 9. First Mixer - Includes the Variable Crystal Oscillator (VCXO) 10. Receiver Bandpass Filter 11. Coil Winding 12. First Transmit Amplifier and Transmit Bandpass Filter 13. Second Transmit Amplifier 14. Third (Final) Transmit Amplifier and Low Pass Filter 15. Final Mechanical Assembly

Click here to download the latest version of ZL2PD's KIT-BUILD INSTRUCTIONS (PDF file : 800k)

Click here to download the latest ZL2PD version of the SCHEMATIC (PDF file : 66k)

Building the Kit

Clicking on the following links will show pictures of various stages in my construction of the KN-Q7 SSB transceiver kitset: Stage 4 - Regulator and Receiver Audio completed Stage 5 - Second Mixer and BFO built Stage 7 - IF amplifier stage built Stage 8 - IF cystal ladder filter Stage 10 -  First mixer, VCXO , and receiver bandpass filter Stage 11 -  Coils wound                     Note: Full instructions, with more pictures, in the kit-build instructions ) Stage 12 -  First Transmitter Amplifier and Transmit Bandpass Filter Stage 13 - Second Transmitter Amplifier Stage 14 - Third (Final) Transmitter Power Amplifier and Low Pass Filter Stage 15 -  Final Mechanical Assembly

The transceiver PCB shown here is almost complete. The next step is to mount it onto the base of the enclosure. The chassis acts as the heatsink for the transceiver. The required mounting holes for the three power devices must be drilled by the kit builder. Not too difficult!

Key Component Specifications

For those interested in the inner workings of the transceiver, or perhaps wanting to make some modifications to improve performance, the following specifications of some of the key devices used in the KN-Q7 may be useful. Just click on the component for more details: DIY7-7 coils NE602 mixer/oscillator MC1350 IF amplifier TDA2822 audio amplifier 2SC3357 1st tx amplifier 2SC1162 2nd tx amplifier IRF640B Final tx amplifier Thanks to the various vendors and alldatasheets.com for many of these PDFs!

Corrections to the ORIGINAL Kit Schematic

For those who just want to update their ORIGINAL schematic which was supplied with the kit documentation, the following list the corrections to the original schematic which was dated 10th May 2007: 1. 1k5 and 10nF feedback components adjacent to 2SC1162 are missing (R25 and C50 on my schematic) 2. Relay coils and protection diodes are not shown (K1- K3 and D8 - D10) 3. 2SC3357 collector resistor is shown as 22 ohms rather than 27 ohms (R18) 4. Base bias resistor is shown as 56 ohms rather than 51 ohms (R22) 5. The optional fit 10k resistor used to provide 8V bias to the microphone is not shown (R7) 6. The 3k3 and 100nF bypass capacitor adjacent to the 10k FET bias preset are not shown (R30 and C55) 7. The 'SQL' label driving the audio mute transistor (Q1) via a 1k5 resistor (R11) is actually connected to +8VT 8. There is an additional +13.8VDC 100nF bypass capacitor adjacent to the 330 ohm resistor (C52) Note: These corrections DO NOT apply to the schematic available from my site

I used this audio oscillator to help test the transceiver. The design of this oscillator is found elsewhere on my website (or just click here to be taken over there)

NOTE:

If you right-click on any of the pictures or schematics on my website and select 'view image', you will see the picture or schematic at full resolution - and the zoom feature will also allow you to see more details if the picture or schematic is able to be enlarged still further

Next Steps

I am already in the process of building some items to match my new KN-Q7 transceiver: An antenna tuner - so I can use a variety of antennas when I take this transceiver on my next holiday A simple SWR meter - I shall probably build this into the antenna tuner A 12V/2A power supply - I've already done some work on this, so details of this should be along soon If I get a bit more time, and as I finish these off, I’ll put the details up on this site. Stay tuned!

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