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Message-ID: <3.0.1.16.19991115104716.2da76d40@mail.cc.kuleuven.ac.be>
Date: Mon, 15 Nov 1999 10:47:16
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: Question: Rotating Shift Encoder
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At 03:37 14/11/99 -0500, you wrote:
>...
>Now my simple question is: how can I simulate a rotary shift decoder in a
>simple manner, so that when I key, the freqency is for example 10 Hz higher
>and then moves down again to the original frequency. I have no idea how
>this is normally realized with the shift encoder, however, I saw that a 5V
>signal is simply pulled to ground over a resistor. If I just key one of
>those encoder port to ground, I already get the frequency shift keying I
>need, however, after keying a couple of times down, the freqnecy is moving
>up or down (in those 10Hz jumps). What I need, I assume, is a kind of time
>sequence to simulate the rotary shift encoder first into one direction and
>then to the other.
>...

An alternative way to generate FSK might be to alter the frequency of the
reference oscillator, this should work for small frequencyshifts (10Hz or
less).
Of course the shift will be a bit frquencydependent but if you stick to the
'digital mode' or visual-CW segments this will be acceptable.

eg. : assuming that you use a 10MHz reference oscillator, a 10 Hz shift on
137600Hz will require a 726.7Hz shift on 10MHz. If you stay within the
freuency range of 137400 to 137800 for digital modes or visual-CW then the
error on the 10Hz shift will limited to 1Hz.

If your reference ocillator is not 'canned' you will need most likely only
need to add 1 capacitor that is switched to get FSK.

73, Rik  ON7YD