[Lowfer] LOWFER receiver conundrum.

[Graham]

Does it have to be a PLL?

A simple DDS such as the AD9850 can use a 10MHz reference and produce 
usable signals for a LO at less than half your reference frequency 
making MF and LF easy targets, even at 4x the required LO for a LF/MF 
softrock is possible.

The AD9851 can also use a 10MHz reference but has an internal x6 
multiplier (10MHz reference becomes 60) and LO frequencies approaching 
10m are possible.

cheers, Graham ve3gtc

On 2015-01-07 00:17, JD wrote:
>>>> I've yet to find anything about using a PLL and reference 
>>>> oscillator to generate a frequency *lower* than the reference 
>>>> oscillator.
>
> It's actually a very common thing, Ben.  The reference _oscillator_ is 
> seldom used directly on its own as the reference _frequency_  in the 
> phase locked loop.  Most often, the crystal or GPS source is divided 
> down to whatever step size you want the PLL to be able to tune in 
> multiples of (10 kHz, 1 kHz, or whatever).
>
> Online, I haven't yet found what I consider to be a really suitable 
> document that takes one from beginner to intermediate level with 
> hands-on examples all the way.  They all seem to go into way too much 
> detail about one aspect or another of the subject, then skip over 
> other rather important points between. Not everything worthwhile is on 
> the Web!  Probably the best route is the good old fashioned printed 
> page, and probably the best general experimenter's reference book on 
> PLLs is the one by Don Lancaster.
>
> A condensed and somewhat mathematical online tutorial is at Analog 
> Devices:
> http://www.analog.com/static/imported-files/tutorials/MT-086.pdf
> I mention it because their bibliography lists some really good, if 
> slightly more advanced, books on PLL design that you might find 
> helpful if you get into the subject seriously.
>
> Good luck.
>
> John
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