475 kHz / 630m Project Notes

This article is a set of notes to contribute towards the club 475 kHz (or 630m) project. Since the project potentially includes the design and build of transmitters, receivers and antenna systems members are encouraged to contribute ideas and information to this article and spawn different articles as necessary.

CW Transmitters

There are a number of transmitter designs on the web. Most seem to use a 3.8MHz or 7.6MHz oscillator divided by 8 or 16 driving a class D or class E PA. Alternatively a DDS may be used.



Power Amplifiers

The most popular MF amplifier designs seem to be those by GW3UEP. There are also details of higher power an class E amplifiers available.


GW3UEP's 25W IRF510 PA

GW3UEP's 100W PA

M1GEO's developments based on GW3UEP's 25W PA

KB5NJD's experiences with GW3UEP's designs

DJ0ABR's 500W PA

G8AGN's DDS + PSU notes (from VK5FQ)

VK1SV's introduction to class E amplifiers and a useful component value calculator

A (very) technical paper about Class E amplifiers (pdf)


Receive Converters and Transverters

There are a few transverter and receive converter designs available, useful ifyou cdon't have a receiver that covers the band.

G3XBM's Transverter

KB5NJD's transverter using G3XBM's design

VK6YSF's Receive Converter

Antenna-Related Info

It's not just antenna designs, we need to consider how transmitter power (roughly) equates to EIRP, and whether our test and measuring equipment is telling us the truth at MF!

KB5NJD / WG2XIQ's article about EIRP

Modifying an MFJ259B to operate on 630m

VE7SL has lots of general 630m info on his blog

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