Santa came early for me 🙂
A KN-Q7A, building the kit as we speak.
A. Crystal Socket
I have selected the 7.080 MHz – 7.100 MHz version of the kit. The supplied crystal is a 15.570 MHz.
In order to cover the 7.110 MHz – 7.130 MHz (till i add a DDS VFO) a second crystal (15.570 MHz) is needed.
To avoid soldering/unsoldering for tests, a have created a crystal socket based on the idea of http://www.qrpkits.com/buildertip03.html
I used a old dip socket, stripped 3 pins from it, removed the central pin and here you are.
B. Low Voltage Regulator
Make sure that you kit contains the upgrade for lower dropout voltage, mine didn’t have a low voltage drop regulator.
If not you will need a:
1×22μF tantalum capacitor
The reason for a low drop out regulator explained:
LM7808 has a minimum input voltage of 10.5V (Vin)
1N5401 has a VF of 1.2V
LM2940-8.0 has a minimum input voltage of 9.4V (Vin)
1N5820 has a VF of 0.475V (0.26V measured on IDLE RX)
1N5401+LM7808 requires at least 11.7 V for operation
1N5820+LM2340-8.0 requires at least 9.875V
A 3S1P has a maximum voltage of (4.2Vx3) 12.6. If we discharge the cells down to 3.3V it’s 9.9 V
Which means i can go portable with a 3S1P LiPo pack and get all the juice out (till we trip the protection circuit)
I did a quick build of a two tone generator from dk7ih
With a 400mVpp signal at microphone input i measured the following on my dummy load (11/12/2016):
Vpp = 40 Volts
Vp(max) = Vpp/2 = 40V/2 = 20 V
Vrms = 0.707 * Vp = 0.707 * 20V = 14.14V
P=V^2/R = (14,14)^2/50 = 4 Watts PEP
Needs a bit more TX alignment to reach the proposed 10 Watt PEP but i think i will leave it as it is from the datasheet
RF output: about 10 W PEP @ 13.8 V
2 A in TX @ 13.8 V
Added 10 Turn Potentiometer
I have replaced the original Tune potentiometer with a 10 Turn Potentiometer. It gives a better feeling on tuning
Suggested part numbers:
I used one from aliexpress (a clone of Burns…) you get what you pay for. Around 2 USD delivered
To be continued