#QCX 4174 Ready for practice test #qcx



Here is my QCX with some personal adjustments (I like small personal adjustments):
Build in battery (15,8V 850mAh LiPO) with BMS
Build in antenna-tuner (i use "random antennas")
Switching Step-down-regulator instead analog regulator (reduces the power consumption at RX noticeably)
Build in touch-paddle, based on ATMEGA 48 (second function - operates as rotary encoder)
Overvoltage protection for PA (useful with battery voltage above 15V and missing load by antenna or dummy)
The enclousure is made of PCB material FR4


Looks very nice!  Everything in one box.

Which switching regulator did you use?  I'm about 2/3 of the way through building mine and was considering
using this one: https://power.murata.com/data/power/oki-78sr.pdf
It's supposed to fit in a 7805 foot print.

It should save significant power when running at higher voltages. I did have some noise concerns, however.
I guess the best thing to do is try it both with the 7805 and the Murata switcher and see if I can find any issues.

-Bill W2WZ


The practice test was negative. My mistake: My tuner tunes to antenna voltage, no control of adaptation to the PA. This caused the PA to overload, causing the MPS2907 to burn. Repair ok. Change tuner is in progress.
I use follow regulator https://www.ebay.de/itm/Mini-DC-DC-4V-12-24V-To-5V-3A-Adjustable-Step-Down-Power-Module-Buck-Converter/272694825804
In my overvoltage-protection the 0,47µ - C is reduced to 10nF
There is a unknown problem on my QCX: Full QSK works fine, Semi QSK not -
no intermission between the characters (version 1.00e)


The tuner has been changed, tuning display by the passive bridge circuit with LED works well.
At 15V, the following values ​​are obtained:
RX 71mA   (with 5V switching regulator, display light on 5V with about 12mA - is sufficiently bright
TX 600mA  5.5W  or  510mA  4.6W  (depending on tuner setting)
The reception reports from the RBN look real