Posts Tagged ‘homebrew’
A simple HF receiver
May 19th, 2010 | 
Author: Before this blog I had a web site with some amateur radio information. It is still out there, but I should close it down or update it totally. Here is one of the projects from those pages which I had great fun with and which is worth adding to this blog. I was quite impressed with the quality of the audio from this receiver which has just seven components (three capacitors, two transistors, a resistor and a transformer). Below is an edit of what was originally written a few years ago.
I constructed this simple receiver having seen the circuit at WB4LFH’s web site which he calls the ‘audion’. This circuit is almost identical to the last circuit on that page, except I changed the inductor connection to the variable capacitor from being a tapped connection to being a transformer coupling.
The inductor was a T50-2 toroid with secondary being 28 turns of enameled copper wire and the primary (connected to the antenna) being two turns. (Remember a ‘turn’ on a toroid is the passing of the wire through the hole). The transistors were 2N3904 types, but you can try any general npn transistor. The tuning capacitor was a air plate type taken from an old radio receiver, likely about 300pF. The circuit was constructed ‘ugly style’ on a small piece of unetched circuit board. Use what you have in your junk box and experiment.
The performance is very good considering the simplicity of this receiver. Below are a set of sound recordings from this receiver. The recordings show how the volume can change (no AGC here!) and that the selectivity is not too good.
If you consider building this receiver please note that these recordings were done with the receiver connected to my external antenna at that time, a G5RV. I tried using a long whip antenna, which I had in the junk box, and there was no discernable reception of a signal with it. So you will likely need to use a good length of wire to act as an antenna. Post a comment if you have any success with this circuit.
Polar Bear on Hontoon Island
Look out Hontoon Island the Polar Bear of Florida is coming your way! Good Friday, 2 April 2010 Polar Bear QRP member #173 (aka K4UPG) will attempt to qualify Hontoon Island as a US Island on the Air by making 25 contacts including at least 2 DXCC entities.
Hontoon Island is a beautiful place for some QRP Portable Ops
Activity will start about 1400Z after the ferry ride over to the island. Plan is to use special callsign K4T for recognition.
Look for us on 30m cw (10.106-10.116 MHz) and 20m cw 14.050-14.070 MHz and on the hour we will check 15m 21.060-21.070. If anyone shows up to assist, will also attempt ssb on 14.250-14.260 MHz island corridor. All ops will be QRP so we’ll need your help to pull us out!
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Fishing is good!
If things go well, our Central Florida QRP group may consider this as a new operating site! If you are in the area, come on and check it out with us.
Hontoon Island closes when the sun goes down!
Thanks to Florida State Parks for the fine pictures!
P.S. We did it 4.2.2010! Over 30 QSO’s update coming! I am TIRED!
