James adds an LM386 amplifier kit to his Heathkit GR-150

Heathkit Explorer Jr. Completed w. screwdriverMany thanks to SWLing Post contributor, James Surprenant (AB1DQ), who shares this update to his review of the Heathkit Explorer Jr. TRF AM radio receiver kit:

With regard to the Heathkit TRF AM receiver kit, I did indeed build my LM386 amplifier.

I was planning on home-brewing it from scratch as the chip is pretty much all you need and there are various proven schematics for the circuit, but in the end I went with a small kit from Nightfire Electronics for $10 plus $5 shipping that I found on Amazon.com.

It was a bit cheaper to buy it in kit form, of course, and then there was the convenience of having all the parts in one place.

Here is a photo of the kit as advertised on Amazon


And here is my build with the Heathkit…

Heathkit + LM 386

I modified the kit to add a 3.5mm input jack, replacing the RCA jack that came with the kit, to make it easier to plug into the Heathkit radio.

I deliberated whether to install the audio amp into the Heathkit cabinet drilling out a couple of holes for the pot shafts. It all would have fit and I could have easily mounted the 3″ 8 ohm speaker to the back panel of the Heathkit radio. In the end, I decided to keep the radio original and mounted the amplifier board on a small piece of wood I found at a hobby store and decided to leave it all exposed. It works well, all things considered.

(Click here to view video on Facebook.)

It worked well and per my original review on SWLing Post, I feel Heathkit should have included such a little amp in the kit – it makes a big difference.

Many thanks for the update, James! That little LM386 amp kit seems like an affordable addition for any receiver lacking an amplifier or adequate audio amplification.

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8 thoughts on “James adds an LM386 amplifier kit to his Heathkit GR-150

      1. sv3auw

        Do you know how much a square inch of breadboard cost?!!! 😉
        There is much overproduction in China, that in a couple of months they will pay us to buy their products! 😉

  1. DL4NO

    Why didn’t you use an amplified computer speaker? It might have cost about the same, including a housing.

    As a power supply you could use an USB power bank that could also suppy the GR-150. Three fresh AA cells might provide in excess of 5 V so the USB voltage should be no problem for the GR-150.

    1. James M. Surprenant

      I actually did use a computer speaker initially, but I always look for opportunities to melt solder and build circuits, it’s all part of my radio hobby.

      Indeed, I agree that a USB power source would work well with the GR-150.

      Many thanks for your kind comments.
      73 de AB1DQ/James 🙂

    2. London Shortwave

      Another reason not to use off-the-shelf speakers: the copious amounts of RFI they inject into just about any receiver circuit. I tried quite a few different ones for my outdoor expeditions (for audio monitoring whilst recording) and they all made radio reception impossible once connected to the radio. I then bought a similar kit from Maplin and it solved the problem. This is the right solution for the radio enthusiast!

      1. DL4NO

        There are power banks that produce RFI. As Dennis showed revently, this needs not be the case.

        Also remember that some antennas are more prone to RFI injection than others. Think back to your portable SDR solution. 🙂


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