DDS spurs

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From: Matthew Balmer (matthew@thebalmers.freeserve.co.uk)
Date: Sat Sep 28 2002 - 11:32:30 CDT


Hi,

This is a second attempt at sending this so apologies if it doubles.

I am interested in experimenting with DDS operating at 14 and 22MHz, control
via a PIC. Spurs seem to be a problem with DDS VFOs, most sources I've read
seem to suggest around -50dBc for the spurs.

Just how much of a problem are these going to be to a high performance
receiver? It is obviously going to be a problem with the spurs mixing with
other signals, and clearly the problem it will cause will depend on the
strength of the signal it mixes with.

I know I could use a "clean-up" PLL but I'm interested, if it won't harm the
performance too much, in just using a simple DDS VFO.

Any comments/experiences would be greatly appreciated.

72/3

Matthew M5EVT


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