[minima] Re: for minima project

  • From: allison <ajp166@xxxxxxxxxxx>
  • To: minima@xxxxxxxxxxxxx
  • Date: Mon, 25 Jul 2016 08:33:39 -0400

On 7/25/16 4:19 AM, Computer Burgas wrote:


In old minima project, after series of tests I found that Si570 has too many harmonics and frequency counter reported me them rather than the fundamental frequency, which means that the mixer and quartz filter probably being down work properly.

SI570 and the 5331 all provide a square wave output which is rich in harmonics. The frequency counter may be
such that it has higher sensitivity at harmonic frequencies or your not coupled adequately.

Also the cost of Si570 in ebay is 2-3 times higher than , for example - AD9851. Moreover BFO also realized unstable frequency. I decided to work towards replacing VFO and BFO with the 2 pcs of AD9851 DDS generators. So with this I will get freq accuracy and easy programmability of LSB and USB in BFO and VFO.

From cost perspective ok. However you need a micro to set it and DDS have spurs. Minimally the DDS will require gain to drive the DBM adequately.

Old minima project will still require better filters and more of them to avoid out of band unwanted signals.

Allison

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