Re: digital vfos

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From: Steven Weber (kd1jv@moose.ncia.net)
Date: Sat Jun 26 1999 - 07:39:44 EDT


> A while back someone on this list (I think) seemed to be
> ready to develop a digital vfo for, I think, $55. That seemed a
> wonderful idea.
>

Hi Jerry,

That would be me.

I'm CCing this to the list, as I have 5 of the VFO's ready to go and
parts for 25 more on hand. Hope I don't get into trouble:-)

There is, of course, a reason why mine only costs $55.00 and the
others cost almost $200 (in some cases). Mine uses a much less
expensive DDS chip, (AD9835) so the highest freq it can produce is
9.5 Mhz. (100 Khz min) and there is no LCD display.

I designed this one to be primarly used to replace diode tuned VFO's
in common QRP rigs, and they rarely use a VFO above 9.5 Mhz, so that
shouldn't be a problem. Also it's very small, only 2" wide by 1.6"
deep and 1/2" tall, so you can fit it in the small box most rigs are
built in. Might even fit in a SST! Requires only round holes for
mounting.

Instead of a LCD digital freq readout, I use four leds as a "LED
Dial". These can be set up to indicate sub bands in your desired
tuning range or light at a specific frequency of interest. Although
you don't know *exactly* the operating freq, you know if your in the
extra portion or the novice portion of a band, and that's all you
really need to know.

Other freatures are 10 Hz, 100 Hz, 250 Hz and 5 Khz tuning rates,
knob tuned with small mechanical encoder, 30 steps per rev.

RIT (tuning rate automaticly set to 25 Hz, original operating freq
and tuning rate restored when disabled, RIT "on" indicated by yellow
led)

A/B freq memo available by adding a N.O. push button (not included)

Built in 10-40 WPM keyer, 2 wpm steps, Iamblic "A" mode, with side
tone, can drive piezo speaker directly.

Tx offset, programmable

Up to three tuning ranges programable, but using this feature
disables the keyer function and requires adding a band selector
switch.

100 Khz to 9.5 Mhz operating range, 1-2V p-p output into 300 ohm
load, output level dependant on freq. Spurs -50dBc or better.
Requires freq counter for set up (programming) 8-14 V DC @ 30 ma.

Comes assembled and tested, as it uses 31 smt parts.
Price is $55.00 + $5.00 S+H priority mail

Steven Weber, KD1JV
633 Champlain St
Berlin, NH 03570

72,
Steve, KD1JV in the white Mountains of New Hampshire
"melt solder"


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