ever build a vfo

[Bill Coleman AA4LR]

On 10/1/98 12:59 AM, GREGORY HEATH at KB2QQM at EMAIL.MSN.COM wrote:

>Hi, I am finding it harder and harder to find a VFO for my Dx-60.  Have any
>of you built a Vfo to use with your rigs. I am interested in something solid
>state  that will work with the dx60. thanks.

Yes, I've built a VFO before. In fact, I built a VFO for use with a DX60
at one point.

A VFO isn't hard to build. Building a STABLE VFO can take some doing. In
my case, I had constructed a 7 MHz VFO for a direct-conversion QRP rig I
designed. The QRP rig never quite worked right. The VFO was mounted in
its own mini-box, and it used a JFET oscillator with a bipolar
emitter-follower as a buffer stage.

I salvaged the VFO and some other circuits and built a companion "box"
for the DX-60. The box contained circuits to join the DX-60 to a SB-301 I
had. This was back in 1985. I still have the box, but no longer have the
DX-60 or SB-301.

In the box is the VFO, a VFO amplifier, a CW sidetone oscillator, and a
key-operated TR switch. The VFO is equipped with a "shift" circuit so the
VFO moves off-frequency during receive. That way, the VFO free runs, but
doesn't mask a QSO. Sidetone is provided by a UJT (which may be rare
these days). The TR switch has a variable "wait" so that the TR switch
doesn't open between elements or characters of code -- only on long
pauses. The VFO amplifier provides additional buffering, and raises the
signal output to something that the tube-type DX-60 can use.

This box worked, and I made all of 4 QSOs with this setup. My problem was
mainly that I was in an apartment at the time and had no usable antennas.

The circuits used were cobbled together from the ARRL handbook, and some
articles in 73 magazine. Tracing down the geneology of the circuit (or
heck, even a complete schematic) would be difficult.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at radio.org
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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