My first HF receiver project is complete.
It’s not fancy. It’s rock-bound with no ability to QSY. It only has a single RF gain control up front. It’s direct conversion, so it hears all signals on both sides of its frequency. It’s bodged together and probably not super durable.But it’s my own, made from scratch, and I couldn’t be more happy. So without further ado, here’s the finished product:
The only filtering present is the handful of passives that sit between the NE602 and the LM386, filtering the audio a bit between converting to baseband and the audio amplification stage. A little experimentation showed that the present passives only seem to round off higher audio frequencies, say about 6 khz. They’re not really meant to enhance selectivity, but just to reduce noise introduced by signals further away from zero beat.
Signals come in clear and hot on this thing! With minimal audio filtering and just a basic front end filter, it’s pretty wide open, but that’s kind of the point – at this point, I’ll take sensitivity over selectivity. Particularly up in the QRS part of the spectrum, I’d rather be able to hear the one guy who’s within 3kHz of my crystal than lose him. Remember, this thing is rockbound, so changing frequencies means swapping in new crystals.
The receiver has gone through several revisions and adjustments in the past couple months. See the original post, changes to the front end, and some power problems for those adventures.
While I’ll probably never really be ‘done’ with this receiver – with tinkering projects, are we ever really done? – it feels great to have it packaged up, in a case, and usable. It’s freeing to have something complete enough to show off.
Hear you on the air!
73