NSH-1
(A single conversion Super Heterodyne 40m band receiver for SWLs & New Comers)
by N.S.HARISANKAR - VU3NSH

Specification and FeaturesSingle Conversion
Stable VFO
BFO with pitch control !!
2W AF output
Roll - off AF filter !!
No wire link or jumper on PCB!!
Two types of antenna input !! All operating controls are at one side !!
Multi pitch for 2 types of ceramic filters
DG FET RF amplifier and mixer
Gain control for RF Amp
Easily available and economical components
3 pole band pass filter

Now a days the art of homebrewing is changed to ‘plug and play’ manner and that leads to the ruin of the real charm of the same and due to this the SWLs and HAMs loosing their skill and knowledge in radio techniques. These kind of guys making lot of pit falls while making their own RF coils, assembling and at alignment. I hope this project ‘NSH 1’ will give some knowledge and a practice about receiver assembling, calibration etc. in ‘do it yourself manner’.

This is a single band solid state amateur band receiver project, meant for SWLs and new comers. The complete sections are on a single PCB and all components for this project are available in the local market. The criteria of this project is simple circuit with low priced components, all operating controls on front panel including BFO pitch control, RF gain control, volume control, tuning and AM - SSB/CW selector etc. for good speech quality audio, this circuit employs a simple speech filter known as AF roll-off filter, which will give good speech quality and it can cut the noises of neighboring stations. I spent 40 days for circuit designing, assembling, testing, calibration, PCB designing etc. I started the first PCB which is manually designed for the test. The main aim is to avoid unwanted jumpers and zigzag connections on the PCB. After testing the PCB is finalized. The track side of the PCB design is as ground plain or called copper pour or polygon type to prevent unwanted QRM - like inter stage signal coupling, leakage and other parasitic problem. The total size of the PCB is 21.5 cm x 9 cm.

I wish to thank VU2ARA, VU2HRS, VU2VWN, VU2ITI, VU2VKC, VU3FID, VU2LLN and SWLs, Mr. Rejeesh, Mr. Sajeesh, Mr. Vinod for giving enormous support and help regarding this project. This project is dedicated to my mother Smt. N.S. Jayavalli and all SWLs and HAMs

Download the complete project document and circuit.

Fig 1. NSH-1 Block Diagram  Fig 2. ‘NSH-1’ Assembled Prototype 7MHz AM/SSB/CW Receiver