https://stream.echo6.co/videos/watch/ca7bfe6c-0e57-4623-b62b-315c5342d2d9 Testing a very basic software defined radio on the 80 and 40 metre amateur bands. Uses the easy to use SDRadio software developed by I2PHD (see www.sdradio.org/ ) and a simple hardware interface which is a direct conversion receiver without audio filter or amplifier stages. Apart from an RF amplifier (not really necessary) all the receiver's gain comes from the computer (microphone in used, not Line in). This is a very 'bare bones' implementation for use with a low-end laptop with a mono soundcard input. Unlike a 'proper' SDR there is no image rejection. Hence signals will appear twice on the spectrum display (one USB and the other LSB) and some juggling may be required to dodge interference. Also signal to noise ratio will never be as good as a single-signal receiver. The hardware unit comprises of (i) transistor VFO (using ceramic resonators for 3.58 MHz (80m) and 7.2 MHz (40m), (ii) buffer stage, (iii) single balanced diode product detector and (iv) transistor RF amplifier (optional). Your favourite direct conversion receiver circuit without audio filtering or amplification would work fine. This unit is USB powered but a 9 volt battery would also be OK if you want to keep it independent from the computer (this also helps reduce interference radiated from the computer). Performance isn't as good as a home station rig but in some aspects is better than a basic direct conversion receiver. The AGC is a bit slow for my liking and it would be good to have an option to switch it off. There is a slight delay between when you adjust a setting and when the resultant audio is produced. A weak signal is generally clearer and less noisy on the commercial rig as well. And tuning can be fiddly when trying to null out an interfering signal on the opposite image (a full SDR with stereo sound card would fix this). Nevertheless for its simplicity this is a good receiver and would be a good beginners project. As a starting point, build a simple direct conversion receiver without the audio filtering or much audio gain. A strong detector - eg a diode single or double balanced type - is suggested. In response to questions about kits, I am not in the kit production business. However circuits and full constructional details appeared in the September and October 2011 issues of the WIA's Amateur Radio magazine ( www.wia.org.au to join/subscribe). In addition you can find the circuit on VK5TM's website ( www.vk5tm.com ). Want to try a more advanced commercially made SDR with a very wide frequency range? Consider something like this: http://ebay.us/gRpGKA (Note: I receive a small commission on sales - no extra cost to you) Contents 0:00 Introduction 0:43 Software 0:49 Inside receiver unit 2:00 Using it 2:55 Examples of signals heard PS: If you liked this video please consider supporting Amateur Radio VK3YE by: Subscribing on YouTube, Checking my books page at https://books.vk3ye.com ​​​​​​​​​​​​​​​​, Shopping on Amazon via: https://amzn.to/3iiDQXv , or, Shopping on eBay via: https://ebay.us/i9DuWP (then if you buy something I'll get a small commission at no cost to you) Sat, 09 May 2026 05:58:57 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://stream.echo6.co https://stream.echo6.co/client/assets/images/icons/icon-512x512.png https://stream.echo6.co/videos/watch/ca7bfe6c-0e57-4623-b62b-315c5342d2d9 All rights reserved, unless otherwise specified in the terms specified at https://stream.echo6.co/about and potential licenses granted by each content's rightholder.