The DDS puts out perhaps a volt far to large for a preamp device. I suspect like everyone else you are clipping. Just take a 2n3904 use it as a common collector/buffer and bias the emitter for a clean cycle and see what level you get. Regrads Paul WB8TSL
On Sat, Jan 17, 2015 at 2:51 AM, Tom Miller <tmiller11...@verizon.net> wrote: > > ----- Original Message ----- From: "d0ct0r" <t...@patoka.org> > To: "Discussion of precise time and frequency measurement" < > time-nuts@febo.com> > Sent: Saturday, January 17, 2015 12:02 AM > Subject: [time-nuts] DDS on AD9852 > > > > >> >> >> Hello, >> >> I would like to ask some advise about the signal distortion I get from >> my DDS project. >> The T-Bolt GPSDO is in use as a REF signal source (10Mhz) for AD9858 >> DDS. This chip has two COS analog outputs which opposite to each other. >> I am using 20x reference multiplier in my project. And I am using Low >> Pass filter and RF amplifier connected to ONE of the COS output. The >> other output has no filter or op-amp on it. Attached is four files with >> OSC screen shots, where the signal which goes through the filter and >> amplifier somehow distorted. In contrary, the signal from another output >> (without filter and op-amp) has near perfect curve. I am using the same >> cable for connection to Oscilloscope.. And I set 5 Mhz output on DDS as >> an example. In this my project I am using Ten-Tec broadband pre-amp. The >> filter is standard Chebyshev Low Pass filter made by MINI-CIRCUITS. >> Model PLP-90 (81 Mhz). >> >> Here is the link to Ten-Tec >> http://www.tentec.com/products/Universal-Low%252dNoise-Broadband-DC-to-1- >> GHz-RF-Preamp-%252d-Model-1001.html >> >> >> Is it normal to have that kind of distortions for the signal, or >> something wrong with design ? >> >> -- >> WBW, >> >> V.P. >> >> > > ------------------------------------------------------------ > -------------------- > > You are overdriving the amplifier. What is the part number of Q1? It looks > like a MAR-xx something. > > The Tentek page does not have any good technical details on the amp that I > could find. What info do you have? > > Regards > > > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.