Hi Graham !
An alternative would be to use hardware like two cascaded active
rectifiers using OP-amps to get the frequency x 4. As those digital
modes do not need linear sine waves on transmit, it is no problem using
even square-wave-tones for modulation. Maybe some filtering is necessary
to not overload the AF-input of the transmitter.
This circuit could be realised as an inline-PCB between soundcard output
and TRX input.
Certainly such a "solution" is not really "elegant", but should do the
trick.
73 de dg3lv Tobias
Am 25.02.2013 13:24, schrieb Graham:
DSP app to multiply tone by 4 ?
One thing that one of the PA (Dutch PA) stations spotted , is the 477
band is a handy divide by 4 from 1.9MHz .. and if you use two
flip-flops , you can divide from 1.9 to 477
Setting the rtty shift x 4 in fl digi 340 HZ , then gives 85 Hz at 477
A problem with the multi tone modes , unless its possible to write a 'dsp'
app , that multiplies the tones by 4 , single tone fixed amplitude in
real-time or slightly after ,
That would open up all the (non linear) modes
to 477 , X2 for 'logic' drive amps, X2 drive, and X4 for conventional on
frequency amps ?
Q Is this a possibility ?
Could something be coded , that either looked like a sound card
, or took audio in , and outputted a multiplied frequency by 2 or 4
Could have delay as long as the delay was fixed ?
G..
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