I have been really careful about estimating power out of an amp. I have an
HP 435B power meter with an 8484A head. Maximum power to the head is
supposed to be 10 microwatts (-20 dBm). I carefully calculate the
attenuation needed to keep the input to the head within this range. If I
estimate a power amp could be putting out 10 watts, I'll use 70 dB of
attenuation.
Same for the NanoVNA. I have used it to adjust VHF preamps that could
possibly put out +20 dBm with a gain of 20 dB. So I'll put 30 dB of
attenuation on the input. So far I haven't burned out either the HP power
meter or the NanoVNA.
Zack W9SZ
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On Mon, Jun 13, 2022 at 1:09 PM Jim Lux <jim@...> wrote:
On 6/13/22 11:06 AM, gfmucci via groups.io wrote:
"What is the most likely way that beginners kill their VNA ?"
Static buildup especially in dry climates. I had one DOA and the vendor
said static buildup killed it.
The second most likely is "transmitting into it", or, more properly,
making S21 measurements on a small amplifier that has output power
bigger than the VNA can take. That 20dB gain block, driven with -10 to 0
dBm puts out +10 to +20, which is more than the VNA can take.
