Message	Date	From	Subject
10749	2015-01-22 07:33:24	Chris Howard w0ep	general question about DDS chips and such
For the various varieties of programmable frequency sources, the Si5351A, Si570, the Analog Devices DDS chips, etc. Is it safe to assume that they can run on a lower frequency clock (C < Cmax) and then produce outputs scaled by C/Cmax ?
10750	2015-01-22 08:26:23	Dana Myers	Re: general question about DDS chips and such

10751	2015-01-22 10:37:04	jorschei	Re: general question about DDS chips and such
Chris, The Si570 has a internal X-tal thad cannot be replaced. The Si5351A has a external X-tal as reference and it possible to test a higher or lower frequency X-tal. The data sheet say 25 or 27 MHz, bud it is interesting to test how high or low the x-tal frequency can be used outside the specification, and measure the harmonics and noise (jitter) of the output. In theory if the the x-tall is 50 MHz and twice the divider for the same output frequency may be the noise will be lower, bud experiments will give the answer. The same for lower x-tal frequency's. 73" Joris PE1KTH

Chris,

The Si570 has a internal X-tal thad cannot be replaced. The Si5351A has a external X-tal as reference and it possible to test a higher or lower frequency X-tal. The data sheet say 25 or 27 MHz, bud it is interesting to test how high or low the x-tal frequency can be used outside the specification, and measure the harmonics and noise (jitter) of the output. In theory if the the x-tall is 50 MHz and twice the divider for the same output frequency may be the noise will be lower, bud experiments will give the answer. The same for lower x-tal frequency's.

73" Joris PE1KTH