--- In [email protected], "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
wrote:
>--snip--
>
> I know that for now the DDS is the only way, and the best way to get
> full HF coverage and into 6 meters. Huff & Puff ideas are yet coming
> along and may result in a kit later in the year or so. I see them
> being used in the tapping into receiver i.f. ideas for 455 kHz and 10.7
> MHz rather than making full HF coverage possible. Some time later on
> in the future that might come about I hope. I am going to use the
> current one I have with this chip from the get go.
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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