Perseus GPSDO

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I modified my Perseus SDR to have a much better and stable frequency using an external GPSDO instead of the internal LO
The internal LO was quite good but had frequency drift during heat up and temperature changes

For the propagation measurements I used for a very long time the internal Perseus clock oscillator

Performance off this oscillator was good enough as long as the temperature in the room is stable

During a search on the internet I found a publication from W7MLG: look here

At first I wanted to try and use this modification also but later decided not to follow his modification

In my opinion the modification from W7MLG was a bit overcomplicated

I do not quite see the need for an extra 80 MHz reference Wenzel oscillator and I wanted to try
and use a GPSDO directly able to deliver a GPS locked 80 MHz signal

Also the input modification from W7MLG using a balanced transformer to get a optimal connection to the AD converter.
The original Perseus clock however uses a single ended clock input
Why should I want to change the single ended clock input, I don't have an idea
 so I decided to use a modification also using the single ended input.

This makes the modification less complicated and in my opinion there is no need to add an extra circuit board into the Perseus

First thing to do is do cut two small traces off the Perseus board to disable the original clock oscillator

In the first picture is shown the two traces of the original oscillator who are cut using a sharp knife

I then added two short wires, the first one on the left to ground and the second on the right to the clock input
These two wires are connected to the small coax

For the 80 MHz oscillator signal I am using a Bodnar GPSDO at 80 MHz at the lowest power setting

For start-up the Perseus the power up sequence needed is:
first the GPSDO needs to be powered and preferably locked to GPS
then the Perseus can be powered
All is working as before.

When the 80 MHz signal is switched off the Perseus software is crashing and needs to be restarted after the 80 MHz is back on.
In case the 80 MHz GPSDO needs a switch off one should first close the Perseus application on the computer,
then the GPSDO can be switched off and after its on again the Perseus application can be started again.

After setting up the system it is needed to clear the previous frequency calibration from the Perseus to have a good frequency readout.
It was very nice to see a signal to be exact on the right frequency and even better that the frequency was no longer wrong if the shack temperature changed.

Not many Hams use the Perseus for very exact frequency receiving but in my propagation measurements
 where I measure changes in a fraction of 1 Hz this modification is a big step forward.