UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Another "Pantry" Rig for the IC-allergic

MrBungle · 5th Jul 2019, 9:25 am

Thanks for the write up mictester. Much appreciated. It's an excellent little circuit.

On the oscillator blocks, the square wave doesn't really matter that much if it's a very low power output. The fundamental signal is what you are mostly interested in and there's plenty of that. I have actually built a small CW beacon that uses a 74AC14 as an osc and PA and a crystal modulated by a PIC12C509 driving a 2n7000 to disconnect the oscillator. The matching circuit between the 74AC14 output and the antenna is done with a naturally low-pass LC network and then followed by a 5 pole LC filter so what hits the antenna is pretty harmonic free. I was surprised at "how digital" a transmitter can be! It's also a lot more efficient than running class A amplifiers through each stage.

5th Jul 2019, 9:25 am	#10
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Another "Pantry" Rig for the IC-allergic Thanks for the write up mictester. Much appreciated. It's an excellent little circuit. On the oscillator blocks, the square wave doesn't really matter that much if it's a very low power output. The fundamental signal is what you are mostly interested in and there's plenty of that. I have actually built a small CW beacon that uses a 74AC14 as an osc and PA and a crystal modulated by a PIC12C509 driving a 2n7000 to disconnect the oscillator. The matching circuit between the 74AC14 output and the antenna is done with a naturally low-pass LC network and then followed by a 5 pole LC filter so what hits the antenna is pretty harmonic free. I was surprised at "how digital" a transmitter can be! It's also a lot more efficient than running class A amplifiers through each stage.