Ham Radio

Most of these circuit I build show using a MAX 232 chip. I used a MAX 202 chip. Using the MAX 202 chip, change the 4 x 10uF caps connected between pins: 1 to 3, 4 to 5, 6 to ground and 2 to +5V, change to 0.1uF caps.

I find it's easier to put 0.1uF caps around the chip than using 10uF caps. You can even solder to the under side of the board without making a mess.

Note! You can NOT use 10uF with the 202 and NOT 0.1uF with the 232 chip. 

This circuit will work with most modern Yaesu transceivers, I have had it working with a VX1R, VX2R, VX5R and a FT7800R. Diodes D1, D3 & D4 are 1N4148 or equivelent, Transistors Q1, Q2, Q3 & Q4 are 2N2222 or BC337, Q6, Q7 are 2N3906 or equivelent. I have also fitted a serial to USB adapter.

The variable caps (C1,C2) are 300pF which are the plate control caps out of a Yaesu FT101 and FT200 and (L1,L2) are  29 turns each and also out of a Yaesu FT101 and FT200. I have used both coils so I can tune up my 80 meter G5RV antenna on 160 meters. I have randomly tapped the coils to get the best results using a twelve position rotary switch. For 10 meters I am only using one turn and for 80 meters I am using 29 turns (all of L1) for 160 meters I am using both L1 and L2 untapped.

 Parts used:

1 x 220 ohm resistor, 5 x 0.1uF, 1 x 10uF caps, 2 x 1N4148 diodes, 1 x 4V7 zener diode, 1 x MAX202 ic

I have been trying to locate an Amidon T-130-2 toroid to build this circuit. The toroid I was looking for is red coloured, but unable to find one; I found a smaller red toroid that works perfectly. The tuning capacitor's measured at 330pF per side. 

This is my home brew AM 80 meter phone and CW transmitter. Using a single EL84 for the output at around 4 Watts. The large transformer in the centre, is a HT power transformer which I use as the modulation transformer.

This transmitter is on the air most Friday evenings at 08:00 utc. using phone on 3.850MHz.