Return to VK3YE projects

Simple transistor receivers and converters for HF A page of videos (normally with circuits) describing and demonstrating simple receivers for shortwave broadcast and amateur bands. A few transistors and other parts is all that's needed to hear signals thousands of kilometres away. These use regenerative, direct conversion or reflex circuits. Operation and stability is generally better on lower HF bands below about 10 or 15 MHz. If you want stable coverage of higher frequency HF bands you can add a crystal-controlled converter to shift higher frequencies down. You can also do the revese, for example using a 20 MHz crystal to shift 7 MHz signals up to 27 MHz where they can be heard on a 27 MHz CB radio. A one transistor superregenerative detector followed by an audio amplifier can hear 27-28 MHz signals from thousands of kilometres away. As well as being hissy (without a squelch circuit) it is not very selective and is confined to AM signals only. However if you add a beat frequency oscillator (operating at 27 MHz or a submltiple) you can resolve single sideband, digital and morse transmissions on a superregen. And selectivity is better too unless signals are very strong. Below are circuits and demonstrations of some simple HF receivers and converters that you might wish to try. Simple 3 - 23 MHz HF regenerative receiver hears shortwave stations and amateurs   A Franklin regenerative receiver   Super simple 7 MHz receiver and notes on RF breakthrough   One transistor direct conversion reflex receiver concept   One transistor direct conversion reflex receiver concept - refined   Demonstration of a chopping board HF receiver as described in Sprat   27 MHz superregenerative receiver   Beat frequency oscillator for above 27 MHz superregen   1.8 MHz to 27 MHz receiving converter   7 MHz to 27 MHz receiving converter   27 MHz to 3 MHz receiving converter   Above 27 MHz to 3 MHz converter in box with FETLer receiver as published in Sprat   My favourite from the above is probably the 3 - 23 MHz regenerative receiver. This has allowed reception of amateur, broadcast and weather stations from far and wide. The Franklin circuit is also excellent and would do even better if put in a proper case. The current sunspot high means many signals on the 27-28 MHz region so I strongly suggest building a receiver or converter for these sometimes neglected frequencies.   Disclosure: I receive a small commission from items purchased through links on this site.

Books by VK3YE Ham Radio Get Started (USA) Australian Ham Radio Handbook (Aust) Hand-carried QRP Antennas More Hand-carried QRP Antennas 99 things you can do with Amateur Radio Getting back into Amateur Radio Minimum QRP Illustrated International Ham Radio Dictionary Make your Passion Pay (ebook writing)   All material on this site (c) Peter Parker VK3YE 1997 - 2024. Material may not be reproduced without permission. Read privacy policy.