[hpsdr] Penelope / Hermes use as VNA: Driver problems?

[Phil Harman]

Hi Raj,

There are a couple of things that will prevent a possible problem.

1. In order to measure Z the output of Hermes will typically be connected
to a bridge. In which case the output will not directly see a S/C.

2. The detector (i.e. receiver) is very sensitive and we can easily afford
to place a pad at the output of Hermes. I can do very reliable Reflection
measurements with -90dBm into the receive input of Hermes. It would be
preferable to place the attenuation at the receiver input, especially when
making measurements on full size 160m antennas, but even so we have plenty
of margin.

3. The PC VNA software will have full control of the signal level from
Hermes and we can program in suitable safeguards.

73 Phil...VK6APH



> ***** High Performance Software Defined Radio Discussion List *****
>
> I have a question regarding use of Hermes or Penelope/Mercury as a VNA.
> I had heard that the driver in both of these was sensitive to low
> impedance and would possibly be damaged if shorted.  How would that
> affect the use as a VNA as a shorted load is a standard calibration.
> Does one need a pad or is one built in to deal with this issue?
>
> Raj, N2RD
> Owner of Penelope/Mercury, Hermes ordered. .
>
> --
> --
> Raj Dewan, N2RD
> FN13fc
>
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