Support QRP CoA Everywhere

Tuesday, 18 August 2009


Lots of interest being generated for this little tcvr from China. (BD4RG)
I built a PFR-3 and KX1 already (PFR-3 on this blog) and I never considered those to be identical rigs although fulfilling similiar use as /P portable rigs. So I thought I'd have a look at what all the fuss was about as some claiming the HB-1A to be very close to the Kx1, and about 1/2 the price.

A JN1GLB photo of the 'kit' he obtained

JN1GLB photo of the rear of the board.

The KX1 and the HB-1A do share a lot of similarities, but the SA602 and LM386 AF chain is not exactly unique to either. Both do use a AD9834 DDS with 50MHz clock but that again appears in a few places.
The HB-1A using a split 2 PIC design with a main DDS/rig control PIC 16F73 and a separate keyer chip PIC 12F629, the KX1 using the single PIC 16F876A to accomplish both.
The mute in KX1 comes from RA4 / 16F876A the HB-1A uses pin 8 /PIC 12F629 keyer. The KX1 mute circuit one uses a pair of J309 HB-1A uses a single 2N7000 to interrupt the AF. If you are going to mute the RX then you have to switch off the input to the LM386 somehow. However, the HB-1A adds an extra mute after the Lm386 as well and the tone output from the pin 5/ PIC 12F629 feeds to the phones. The KX1 feeds the side tone pitch and level from 16F876A (RA5) .
The HB-1A has a very similar IF filter with 4 common 4.1952 MHz crystals. The KX1 IF being at 4.913MHz. The filter band width is controlled by a rotary pot in KX1 but through the PIC 16F73 in HB-1A.
The HB-1A used SMT components throughout. KX1 through hole.
The HB-1A reports battery voltage and the frequency display is to 5 signifiant figures (10Hz resolution). KX1 to 1kHz resolution.
I find the HB-1A interesting as I have many of the components in the junk box (and in SMT form!) and I have a couple of spare keyer PIC 12F629 and a selection of PIC/AVR AD DDS chips and some Si570, perhaps an alternative homebrew version of this might be a fun project.

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