----- Original Message -----
From: "d0ct0r" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
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
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