[minima] VFO 100K pot question
- From: "Steve VK2SJA" <vk2sja@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Wed, 22 Jan 2014 16:31:49 +1100
Hi All,
Wayne VK3ALK, sent me an e-mail off-list asking a couple of questions. I
replied as best able. With his permission I thought others may have
similar questions and so I'm posting my response back here.
Hi Wayne,
> Just a question or 2 if thats OK....
>
No problem at all. Asking the list members rather than me may get better
quality answers though <big grin>.
> The band switch.....does that switch in frequency steps maybe 1 Mhz etc:
> and not sure just how fine tune that 100K pot would be...
The 100K pot for tuning is as clever as it is unusual. It is not
conventional. It is being used as a control pot for a jog-shuttle style
tuning arrangement like you would find on a VCR. If the pot is
approximately centred then nothing happens. Turn it clock-wise and you
start to tune up in frequency (continuous tuning coverage with no band
stops). The further clock-wise you turn the knob the faster you jump
upwards in frequency. Turning the control anti-clockwise from centre does
the reverse and tunes down in frequency. The detail for all of this is
hidden in the code for the Arduino Sketch (aka program).
The 'tuning steps' are currently set in software as:-
3Hz
10Hz
30Hz
100hz
300Hz
1kHz
3kHz
1MHz
This way of tuning will give precise frequency control from DC to daylight
with just one common garden variety 100K linear pot. Without even
resorting to the complexity/expense of a somewhat harder to get rotary
encoder. The simplicity of design is actually quite brilliant.
But it is going to take some getting used to! And some people may just
hate it. I'm not sure that even I will like it. But I'm certainly going to
keep an open mind and give it a good try. If I truly find this method of
tuning awful then it is easy enough to add my own rotary encoder. After
all the entire design is "Open" and hack-able. And the source code is
freely available.
> Also the serial port socket pin numbers to the ARDUINO would they be pins
> 2,3 and gnd...?
Yes, if my reading of the circuit and code is correct.
> Apart from all that its such an interesting design that I just have to
> build this thing....
Same.
Let me know how you get on.
73, Steve
VK2SJA
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