A perfect controller for a simple repeater or link,
or portable/solar powered system.
This circuit originally appeared in the February 1997 issue of QST Magazine, "Build a $60 Talking Repeater Controller" by Jeff Otterson N1KDO, Peter Gailunas KA1OKQ, and Rich Cox N1LTL. This article documents a kit that NHRC puts out called the NHRC-2 controller. As shown in the article, this controller utilizes a voice storage chip and a PIC microcontroller that oversees timing and control. I really wasn't interested in the voice part of it, all I really wanted was a simple repeater controller that I could interface to a couple of radios and make a simple repeater or link. So what I've done is stripped out the voice-specific components and laid out a fairly small PCB (2.25x2.5") to create this simple controller. The source code for the PIC is available for free from NHRC's website, along with a complete documentation package. My construction details are available for download below.
You can download the complete construction "package" from NHRC that
give the original NHRC-2 schematics and materials list, most of the
sourced from Digi-Key. The documentation package I supply below are all
the changes I've done to build the trimmed down version. I suggest you
both because it would be a lot of work to duplicate the already
documentation that NHRC provides. I'm providing all of the PCB artwork
free, no strings attached. I don't want NHRC thinking I'm trying to
make a buck off of their design efforts. This project is an easy one
have, or have access to PCB fabrication facilities (it's a single-sided
with a groundplane), and a way to program a PIC microcontroller.
There are numerous sites on the web that describe simple and
PIC programmers for the PC (including QST magazine) so it's probably
it to put one together and have around for future projects. I use a
Plus programmer from Microchip and am very happy with it.
I've purchased and assembled a number of NHRC-4 kits from NHRC over the past few years and find that the NHRC-2 operates identically, though with fewer features. To test the prototype of my "basic" NHRC-2 I put it in a box with a couple of 2M HT's:
A couple of old Motorola MX's in a box, along with the NHRC-2
and an audio equalizer. This portable repeater can operate on
a 7Ah gel-cell battery for a couple of days.
Along with the 5-band communications equalizer (also documented on this site) this portable repeater sounds like a real repeater- well, it is! The NHRC has all the timers and control functions you need, and the equalizer gives almost simplex quality audio. These two projects together make a great pair if you're building a simple, inexpensive, or portable repeater or link.
PDF file at NHRC
and HEX files