Topband: Digital mode spurious issues

[Mike Waters]

As utterly simple as it is to shift a VFO, it's almost hard to believe that
any major manufacturer would do it with audio.

When I was heavily into HF RTTY software development years ago, it was a
trivial thing to FSK my Collins 32S-3's VFO. I just connected one pin of
the RS-232 port through a resistor to a switching diode and trimmer
capacitor connected to the VFO tube socket. It turned out to be much
superior to using audio. It was the only way I could keep the amplitude of
the mark and space freqs exactly the same, which turned out to be very
important when conditions were less than ideal.

If rig manufacturers are not informed of this need, we can expect little to
change.

73, Mike
www.w0btu.com

On Tue, Dec 31, 2013 at 1:21 PM, Tom W8JI <w8ji at w8ji.com> wrote:

> In my FT-1000D, if you try to use FSK mode for RTTY it turns out that the
>> rig is still running AFSK, using an internal audio source.
>>
>
>  It would be much better to actually shift a carrier, and not do the
> baseband audio signal...
>