[time-nuts] Ideas for a long-wave receiver sought

Leigh L. Klotz, Jr. WA5ZNU Leigh at WA5ZNU.org
Tue Jun 23 19:34:10 EDT 2009


Are you doing DGPS?

An an alterative to the roll-your-own SDR, tou can build a direct
conversion small receiver or IF converter with a SA602 chip, which
contains a Gilbert cell mixer and a local oscillator.

Here is a board that will do most of what you want, if you're willing to
live with the SA602 limitation.
http://home.att.net/~jacksonharbor/lfconv.htm

You will get out of this board LO + (0 to 500 Khz), which you can the
receive with an existing receiver that can receive the LO frequency.  It
comes with 4.0 and 10.0 MHz crystals.

Here's an article about better input filtering against AM broadcast band
interference, which will be useful for you no matter what route you take
for LF and VLF reception.

http://www.cliftonlaboratories.com/jackson_harbor_press_vlf_converter.htm

There are many ham and non-hams who are using very low bit-rate signals in
LF and VLF at micro power levels.  As a result, they care about frequency
stability, and some are building their own RX equipment.  Here's a random
sample: http://www.qrss.thersgb.net/Receiving-QRSS.html .  Murray Greenman
who is a member of this group did some pioneering work in VLF TX using the
FE5680A as a transmitter, and he may have something to contribute on RX as
well.

If you need better phase noise and frequency stability, you won't get that
from a product like the SA602, not the least because of its internal
oscillator.  You can build a receiver or IF converter yourself out of
discrete mixers from Mini-Circuits, but you'll likely need a preamp as
well as they generally require higher drive points (more loss), and output
filters as well to deal with the image rejection.

Leigh.

> Hi
>
> I want to build a small, cheap, yet precise long-wave receiver which
> can be
> tuned from the computer in the 2KHz - 200 KHz range (the intended use
> is to receive various time signal stations).
>
> Does a chip for such a receiver exist?  Should I take the SDR route?
> I designed a DCF77 receivers some years ago, but I need something
> more flexible (and a bit more modern...)
>
> - Marc Balmer
>






More information about the time-nuts mailing list