Fabio Morsani 2021/01/12 22:46
Thanks Steve for your info.
I agree with your comments, but to measure the crystal response with a
frequency sweeping
of a continous source and manually entering the sweep parameters it seems
to me to be
a simple task because I did it without effort (a DDS and a microcontroller,
a SWR resistive bridge
with diodes and linearization circuit for them).
To measure the crystal parameters is also easy in 50 Ohms systems, as you
seen in my post (formulas found somewhere in the radioamateurs literature)
if you can see the -3 dB points in the displayed curve.
110-120 dB of dynamic is really challenging also in the filter fixture,
cables
and additional shielding is often necessary.
I will use for that my old HP analyzer.
F.
Il giorno dom 10 gen 2021 alle ore 18:00 Stephen Laurence <
Gaslaurence@gmail.com> ha scritto:
> I am a bit late in replying to this, but......
> Possible solutions....
>
> 1. Get a v2 or v2N and install the Obijan software on it. It is
> relatively easy to change/update the software for when you need it for
> crystals and reinstall the most recent software for general use when you
> are done on the crystals.
>
> 2. Get a v1 nanovna (eg h4 with a decent screen) as a second device. A
> mere £45 or so, but as most crystals and crystal filters are below 150mhz,
> the performance of a v1 on its fundamental will probably be satisfactory.
> The dynamic range above 300mhz is much worse than the v2, especially if you
> tweak the v2 a bit (a few extra capacitors, a few ferrite plates around the
> circuit board to suppress leakage) and you then (well, I do) have 60db
> dynamic range up to 3ghz.
>
> You will never get down to 110db below passband (as in the previous post)
> with either solution, however. The nanovnas can however be put in your
> pocket. The gear for displaying 110db filter skirts will give you a hernia
> moving it about and if you get modern pro kit, you may have to mortgage the
> house.
>
> The cost of a v2N plus a v1H4 is no more than two tanks of petrol for most
> cars.
>
> Steve L
>
>
>