Monday, March 15, 2021

Belka-DX with VLF converter

Jackson Harbor converter & Belka-DX
With the Belka-DX only covering the upper 200 kHz of the AM broadcast band I decided to see what the outcome might be if I paired it with one of the first kits I ever built - a VLF converter from Jackson Harbor Press.

The heart of the converter is a 10 MHz (or 4 MHz - both crystals are included) oscillator. This LO signal is mixed with the incoming LF signal from an antenna and their sum is the output. So a 200 kHz signal becomes 10.200 MHz, receivable on any 30m receiver.

The converter is only $14 ($17 with filter components designed to reduce AM broadcast QRM). No case is included - I bought mine at Fry's...remember them? RIP.

Years ago Palomar Engineers sold a VLF-to-80m converter and I had one as a teen in the late 70's. Their ads enticed me with the ability to "hear submarine communications". I never heard any submarines with it but, years later, I would hear them very clearly - no radio needed.

K1EL started to offer a converter kit but it never got off the ground. So to my knowledge, the Jackson Harbor, if not the only such converter, is almost certainly the least expensive. And it works quite well.

I added the filter components to my converter but I may remove them. At the time, I wasn't interested in

Size comparison or mating ritual?

AM BCB DXing, but now, even though I can easily receive strong local AM stations, I wonder what weak stations I might be able to hear that I can't with the components in place.

The intended frequency range of the converter is that of non-directional beacons, operated near airports around the country. The new 630m (472-479 kHz) band is also covered.

The converter is working quite well with the Belka-DX at opening up a new part of the radio spectrum.




  1. NDB/ADF beacons are interesting to listen to. They transmit a cw ident at low power. 73 Ron

    1. Hi Ron,

      It used to be a challenge to listen for distant ones (and today they would serve as propagation indicators for the 630m band) but they are slowly going away & being replaced by GPS-derived ADS-B.

      73 - John

    2. Yes, ADS-B out (Do260B) that is :-) 73 Ron PA2RF