KN-Q7A

Santa came early for me 🙂

A KN-Q7A, building the kit as we speak.

Finished KN-Q7A.

KN-Q7A

Changelog

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.
KN-Q7A crystal socket

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:
1xLM2940-8.0
1×22μF tantalum capacitor
1x1N5820

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)

Measurements

I did a quick build of a two tone generator from dk7ih
https://radiotransmitter.wordpress.com/2016/01/07/a-simple-2-tone-generator-for-testing-the-linearity-of-ssb-transmitters/

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:
Vishay 534-1-1-103
Burns 3590S-2-103L

I used one from aliexpress (a clone of Burns…) you get what you pay for. Around 2 USD delivered

To be continued

1 Comment on “KN-Q7A

  1. It is truly a nice and helpful piece of information. I am glad that you simply shared this helpful info with us. And also thank you for your detailed explain. thanks

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