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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)


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