[TenTec] PTO Issues

[Dr. Gerald N. Johnson]

DDS may have their place but a transceiver VFO may not be one of them 
for the present state of the art. They can display low phase noise but 
over a broad background spectrum of coherent closely spaced spurs 
accompanied by a few spurs with significant strength. They are improving 
and using a smaller fraction of their possible frequency range sometimes 
allows enough major spur free range for something like a Tentec VFO. 
That can require using a UHF or 1 GHz clock and taking much care with 
that clock to not introduce lots of phase noise with the on chip phase 
locked loop multiplier with an inadequate loop filter.

One of the best references I know for them and for designs for ham gear 
in general is the ARRL book titled Experimental Methods in RF Design, 
ARRL number 9239, by Wes Hayward, W7ZOI, Rick Campbell, KK7B, and Bob 
Larkin, W7PUA, radio
gurus of the highest order.

73, Jerry, K0CQ


On 11/26/2010 5:11 PM, Bwana Bob wrote:
> I have seen ads in the radio magazines for a DDS VFO. It's not
> advertised as a replacement for any current VFO, but it might do the
> job. It would be an interesting science project.
>
>               73,
>
>               Bob WB2VUF
>
>