[time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Thu Dec 22 17:45:50 EST 2016


On 22 December 2016 at 02:54, Scott McGrath <scmcgrath at gmail.com> wrote:

> Can you use the VNA as a receiver? And determine whether the 100Hz shift
> is also seen on the VNA
>

The VNA has what's called "tuned receiver" mode, but it is very poorly
documented - or at least I've never seen it well documented.


I tried a few different things.

1) Put the sweep generator into the VNA using tuned-receiver mode. Both
were locked to GPS. The signal generator appears in the middle of the
screen, and whilst one can't say a lot about the quality, there's no doubt
that the position of the peak never moves `100 Hz.

2) Put the signal generator into the spectrum analyzer. This does show some
odd results sometimes, but I'm always a bit concerned that these might
internally generated signals, as whatever source on connects to the SA, it
brings up a lot of spurious signals. There's currently no preselector on
this, although I do have one in a box.

But there is some evidence that maybe the oscillator is moving. But I'm not
100% convinced.

3) Connected the source output of the VNA to the spectrum analyzer. The SA
shows the source is far from clean - much poorer than the signal
generator.  So I think I can conclude that the source in the VNA is quite
poor, which is what I expected to be honest. There is not even a
specification for phase noise on this.

So any thoughts of mixing the VNA source with the signal generator will be
a complete waste of time.

I think I can conclude that attempting to use the VNA in any source of
measurement or as a signal source will just not work.


Dave
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