21 Feb 2012

A 160m AM local natter rig

Further to my post a few days ago about possible bands to use for a very local "natter link" over a 3km path between G6ALB and here, my thoughts are turning to 160m, partly for nostalgic reasons. This is where I first started my ham radio operating with a small 400mW AM transmitter from Practical Wireless (Dec 67 I think).

Although 160m is VERY noisy now, especially at night, I figure that 100mW AM will be enough to kill the QRM/QRN over such a short distance. So, I am gathering ideas for something incredibly simple to build.

For the TX the most sensible rig would be a crystal oscillator (or ceramic oscillator) followed by a buffer and series modulated PA using the modulation circuit from the 2m AM Fredbox. On receive, either a regen receiver (operating just out of oscillation) or even an MK484 (like the ZN414) single chip receiver are worth a try.

This would be no DX rig, just a very basic transceiver to get me into the next village and not much further. I'll keep you posted. Incidentally I am unable to do much building right now as my house is in the middle of some redecoration. I can't find anything!

3 comments:

Anonymous said...

Hello Roger

I remember the POPIT transmitter that appeared in Sprat in the 1990's.
The oscillator stage used a oscillator coil from a scrap MW transistor radio. RX would be no problem just shift the local osc of a AM radio up to cover 160 Meters.
A loopstick variable cap out of a scrap transistor radio could be used as a wave trap coupled to your external antena.

Tony

Anonymous said...

Roger

Sir Clive Sinclair's Transistor pocket book No 2 shows a circuit for a three transistor transmitter for Topband. He claimed at the time to get a range of 1 mile

Tony

Roger said...

Tony,

Something along the lines of the Popit is what I'll be doing. I have this article and some similar designs from Practical Wireless somewhere in a file.