Mayhem on AmRad 40 m. band

[Mike Watterson]

A QSO between Leeds and Glasgow using a basic transmitter built with an EF91 and a few 6L6's and the receiver a home made regenerative , that's amateur radio to me.

That's only one aspect of Amateur radio, purely 1950s flavour. Why not EF50s and an 807? Or an FPGA. Amateur Radio started even before voice broadcast radio, certainly before 1909. Some still do CW, though a spark-gap transmitter won't meet the licence conditions today.

You'd need to build your own gear for 137 kHz (2200m) and 475 kHz (630m). Also some countries (Ireland) have most of 30MHz to 50MHz (Approx 40 MHz is gaining interest). Few commercial rigs have 70 MHz (4m). I've used VHF & UHF Transverters in the past on valve hybrid FT101ZD.

I've experimented with using SMPSU FETS for HF. Certainly easier 2200m to 160m than 80m to 10m.

I've experimented with modified commercial 2.4GHz and 10.45 GHz gear as transverters (using the FT817ND on VHF/UHF) and with kits.

I've experimented with Analogue PAL and FM at 1.2GHz and 2.4GHz. DVB-C and H.264 modulation at 10.45 GHz with 6 MHz channel using a PCI card in a PC. Also for a work project DOCSIS using 2MHz downnlink channel . Recently I got a cheap DVB-T modulator (HD H.264) with HDMI loop through input. It will need a converter to do an Amateur band.

Then there is SDR using your own design on an FPGA board. Experiment with better than 96KHz sampling. Challenging to get high sample rate and dynamic range. There are FPGA experts here! I did get some FPGA dev kits but I decided I wasn't interested in using 96 kHZ sampling and more useful ADCs was a lot of money and risk. I did also look at doing a polar mode modulator/transmitter which seems attractive (Class C power amp for phase and supply from a class D power amp to set the amplitude). It can do AM, SSB, FM, QPSK, QAM whatever with suitable drive from an FPGA. Turns out that a Polar Amp based transmitter is a simple idea that's really hard to implement. maybe achievable for 2200m and 630m.