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Andy > PIC
If the execute times of PIC routines are
not subject to IRQ ..or if they are , could be in
a predictable pattern , assuming nothing else was 'going on'
Then , the PIC alone would produce a reasonable
drive [ square wave or pulse] for a
class e/d logic divider chain , there being no
need [lf/mf] for the ppl or dds ?
how fast , will a pic run?
73-G,
Sent: Sunday, March 27, 2016 9:04 PM
Subject: Re: [rsgb_lf_group] RE: Cheap and nasty sources - was LF:
DK7FC WSPR bad quality problem
If you are referring to the close spaced lines making up the
spectrum of the two strong signals, from teh plot you show they appear to be
about 1.5Hz spacing. This is the WSPR symbol rate (actually 1.465Hz)
so the lines visible are the natural sidebands from the WSPR waveform.
I'd be surprised if an DDS itself were generating 100Hz sidebands on its
own. Especially a more modern one like the AD9859. Even the
venerable AD9850 doesn't generate stuff only 40dB down. So I'd
still look for other means of 100Hz leakage. Perhaps getting onto
the reference source. I assume the two stations both
reporting 100Hz sidebands are using identical generating hardware ?
I use an AD9852 for WSPR and generationg MFSK modes generally, a device
perhaps bit a bit older than the AD9859, but the same family, and it is
certainly clean down to at least -60dBc. When driven from a higher clock
frequency, better still.
Andy G4JNT
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