On 07/05/2014 12:32 AM, Rob wrote:
Eric Weaver wrote:
So pardon my ignorance, what's the hip PLL or at least
counter/phase-detector these days?

Hip these days is not to use a PLL but use an NCO.
Of course there are differences in the spurious and noise output.

Fair enough. The Si570 and 571 look pretty sweet, but are a bit spendy
on something I was hoping to make a bunch of.



However, when still using a PLL and using it for amateur purposes
(small steps relative to the frequency), at least go for a dual-modulus
system. Else the phase comparator has to operate at the frequency of
the channel step, or even at a fraction of that when a fixed prescaler
is required in front of the programmable divider. As the MC145151
at best operates up to 25 MHz, you often will require a prescaler.
A low phase comparator frequency means a slow loop.

Given that it'll power up and stay on channel a long-ish time, that may
not be a bad thing, but point taken. It need not tune every finest step.



The MC145152 is a dual-modulus version. However, note that with a
dual-modulus system it is more complicated to generate the setting
information, probably requiring a microcontroller. Once you are going
to need that, it is easier to use a more modern IC programmed using I2C.



I guess it's time to hunker down and learn to program an Arduino or
Propeller...

Eric Weaver wrote:
I guess it's time to hunker down and learn to program an Arduino or
Propeller...

When you want to build it entirely yourself, probably yes.

Of course there are many existing designs like this:

http://sdr-kits.net/PA0KLT_Description.html

On 07/06/2014 09:56 AM, Rob wrote:
Eric Weaver wrote:
I guess it's time to hunker down and learn to program an Arduino or
Propeller...

When you want to build it entirely yourself, probably yes.

Well yeah point of personal pride, and all...



Of course there are many existing designs like this:

http://sdr-kits.net/PA0KLT_Description.html


Not a bad deal for around 50 bucks 'murrican. Even when you count the
shipping. Thanks!