Hi all,

here is the follow up of this project. Schematic diagram is attached, the Bascom SW can be found on this link in the Download section of my web page.

Click to image to get full PDF schematics.

On the schematics I need to add some explanations.IC5 is basically not needed if the board is about to be powered from 12V. IC5 was added in case that the board was powered directly from LiPo cell (nice feature for Portable work where we need every Watthour from the battery). Fully powered LiPo can have 4.5V, while it's normal voltage is below 4V, which may cause that LCD might not  have propper contrast, hence we need IC5 to add that much negative voltage so that LCD displays in order. If you ommit IC5 then the middle contact of J2 should be connected directly to GND.

On the board you will find also microphone preamplifier. This was added after during tests electret mike did not perform well enough. You may want to adjust amplification of the preamp around Q2 and change R10 - smaller R10 means smaller amplification. On this schematics a dynamic microphone was used.

Perhaps you'd want firstly to try your electret mike without Q2. In this case you do not need to use R10, C23 (and Q2) and connect electret mike to junction R1/C3.

Jumper J1 was meant to achieve higher amplification of the LM386. During testing I have seen that LM386 has enough amplification with J1 open, but you may want to try that yourself.

SP2 is active buzzer, which sounds when we confirm settings done with encoder.

The Bascom program cannot be described in few lines, but it's also rather well commented so there should be no problem when you want to modify it. This version of the programme is for 134 to 174 MHz band, while I am already preparing 400 to 470 MHz version.

Best regards

Jurij