content/10MHz_ref_2.rst

==========================================
 Building a bench 10MHz reference: part 2
==========================================

:author: David Douard
:Category: Electronics
:Tags: test equipment, 10MHz, Rubidium
:series: 10MHz Bench Reference Standard
:series_index: 2

This is a quick follow-up of the `first part`_ of this series.

I've received a few parts from digikey, including a couple of 22µH
Sumida CLS62 inductors (I bought two of them in case I f**k up one of
them trying to solder it with my Weller WS50 iron).

Desoldering and soldering SMD parts without an air flow station is a
bit tricky, but eventually I succeded in replacing the broken inductor.

.. image:: {static}/images/freq_ref/extron_fixed.jpg
	   :alt: The Extron Video Distribution Amplifier fixed with a
                 new inductor for its small DC-DC converter.

Now the "video" amplifier works like a charm. The 10MHz signal is
nicely amplified:

.. image:: {static}/images/freq_ref/extron_working_10MHz.jpg
	   :alt: The Extron Video Distribution Amplifier dispatching a
                 10MHz signal to several equipments.

At 10Mhz, the amplifier dephase the signal of about 20ns (ie. 72
deg). We can also note that (the input impedance of the Extron
amplifier is set to 75 ohm, while my scope is at 1 Mohm; I should try
using the input of my scope set at 50ohm) that the amplification
factor is exactly x2.

.. image:: {static}/images/freq_ref/extron_dephasing_10MHz.jpg
	   :alt: The Extron Video Distribution Amplifier dephasing at 10MHz.

What I need to check carefully now is if all the outputs of the
amplifier are perfectly in phase.

It's amusing that a few days ago, FlyingHacker_ did post a `new thread
on the EEVBlog`_ forum in which he explain that he uses exactly the
same distribution amplifier to provide a 10MHz reference to several
test equipments. Exactly what I have in mind with mine!

One thing I will probably not do is adapting the input/output
impedance (from 75 ohm to 50 ohm). I'm pretty sure it will work fine
as is. We'll see if it provoque some side effects (especioally on the
phase of the signal).

.. _FlyingHacker: http://www.eevblog.com/forum/profile/?u=110591
.. _`new thread on the EEVBlog`: http://www.eevblog.com/forum/projects/distribution-amp-%28for-reference-frequency-standard-or-otherwise%29/msg893851/


.. _`first part`: {static}/10MHz_ref.rst