[time-nuts] Update -- Comparing 10 MHz Oscillators at 10 GHz
Lester at veenstras.com
Thu Jan 27 07:01:16 UTC 2011
Another thought , I have done this with a pair of synth sig gens:
The brik's designs are such that you can typically get them to phase lock at
harmonics of 100 MHz around the nominal. So you should be able to get one
to phase lock at 10.1 or 9.9 GHz, giving you a 100 MHz offset beat note from
the mixer, suitable for analysis by most prosaic test equipment.
On simple way to examine the quality of 10 GHz multiplication is simply to
listen to the 100 MHz beat with a SSB receiver. Another interesting tool is
to put the 100 MHz into an oscope with the sweep synced to the original 100
MHz, or set up as a XY display.
Lester B Veenstra MØYCM K1YCM
lester at veenstras.com
m0ycm at veenstras.com
k1ycm at veenstras.com
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From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Brucekareen at aol.com
Sent: Thursday, January 27, 2011 12:21 AM
To: time-nuts at febo.com
Subject: [time-nuts] Update -- Comparing 10 MHz Oscillators at 10 GHz
Thanks to some help from Joe Ruggieri, I finally managed to get a pair of
10.000 GHz microwave "brick" oscillators phase-locked to 100 MHz inputs.
These require an input of about 0 dBm at 100 MHz and have an output of about
+ 13 dBm at 10 GHz. To gauge whether or not loop noise would interfere
with using these to compare 10 MHz oscillators, I assembled the following
setup as I have not yet constructed the required 10 MHz to 100 MHz
Both 10 GHz microwave bricks were driven through a splitter from an HP
signal generator locked to 100 MHz. The 10 GHz output of one brick was
through an HP X885A phase-shifter equipped with WG/coax adapters and on to
one input of an Anaren hybrid combiner. The output of the other brick was
routed through a 0-10 dB SMA attenuator then on to the combiner. The
reject side of the combiner was terminated. The main combiner output was
routed through a 10 dB attenuator to a Systron-Donner coaxial detector.
output of the detector was monitored with a digital voltmeter.
First the phase shifter and attenuator were adjusted to cause the two
sources to arrive at the combiner with equal amplitudes and 180 degrees out
phase and produce a null at the detector output. I measured as little as
0.01 millivolt on the DVM at the null point. Then the phase-shifter was
adjusted to rotate the phase 180 degrees to place the combiner inputs in
phase. The detector output was about 128 millivolts.
This experiment seems to confirm the earlier results by Ulrich Bangert and
his friend that noise does not appear to be a problem with this method for
rapid frequency comparison. However it would be convenient to have an
attenuator and phase shifter to null the sources.
Bruce Hunter, KG6OJI.
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