80M CW QRP rig


Posted on Feb 5, 2014

After some time of no building activity, the dark afternoons and less busy week-ends has come finally. Perfect time of the season to build a new rig. See what is being done on my bench. I like this way of start, because of easy modelling a components layout. Say, that`s enough experiments with NE612. The heart of the receiver is popular Motorola c


80M CW QRP rig
Click here to download the full size of the above Circuit.

hip MC 3362. Not much Ham applications are available. That`s my pleasure to go. This is very convenient and gives opportunity to select best circuit, best value and best component. I have changed IF frequency as well as VFO frequency triple times. Finally remained on 8MHz RF and corresponding VFO, which seems to be very stable. I don`t have final schematic because there are so many ways to develope. My favourite "universal breadboard" has changed into protoboard, but I am trying to develope future printing circuit based on above "training". Every component is carefuly selected and placed. Schematic diagram is corrected in parallel. The biggest problem was the VFO stability. I had to recall experience of many Hams and myself to find a solution for drifting parameters of coil, capacitors and IC`s internal varactor diode. Compensation wasn`t easy but finally I used poly cap, T50-6 ( yellow core works better than red) and ceramic trimmer capacitor. The overall drift is very low. 170 Hz within first 5 minutes and less than 50Hz in following hours. I tried varactor tuned four crystal ladder filter for the first time. Works fine The Contest ended with satisfactory score - 312 QSOs, 34(!)zones and 82 countries only. This counts for 95k points. Just after the contest I decided to eventually finish prototyping and commence PC board project for future kit. Below you can see working prototype-clean. I worked OK1DSS today (11th of...




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