Grant,
This seems to me (Amateur) a good way to go. It makes a lot of sense
to a non-technical person. The trick is the PC board, a "solder-able"
device, and some software. Devices with several dozen pins on the
bottom, hidden from view, looks CHALLENGING. I have considered Huff &
Puff VFOs, and have the parts on-hand, but I keep coming back to a
DDS type solution for the SDR. I do not have a problem with switching
front-end filters and in fact I might use a "preselector" arrangement
since I am used to that in my old TS-520S.
Anyhow, I would hope that this avenue is pursued to see if it is
practical for the Amateur Hams to take a crack at.
Thanks,
Dick N3HKN
> There is another way of generating the LO for a general coverage
radio
> - use a microwave phase locked loop and divide the output down to
the
> wanted freqeuncy. ICs such as the AD4252 have two PLLs on-chip; it
is
> possible to use the programmable divider in the auxillary PLL as the
> divider. This will give very good phase noise because the phase
noise
> and phase-related spurs are reduced by 6dB for every halving of the
> freqeuncy. For example, using a PLL at 1.5GHz with (say) -100dBc
> phase noise will give a reduction in phase noise of 35dB, i.e. -
135dBc
> which is good for most applications. Using a better VCO will give
> better final phase noise. Phas noise will get better at lower
> frequnecies, the most critical bands are probably 14MHz in the USA
and
> 7/3.5MHz in Europe.
>
> The Ten-Tec Orion uses a DDS/PLL hybrid synthesiser running at
> 500-600MHz which is divided down to HF. Going to higher frequencies
> eliminates the need for the DDS, as the step size can be accomodated
> by the PLL.
>
> regards
>
> Grant
>
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