Sort of related -
I need to make an attenuator for my FT817 on transmit as a 432 MHz
microwave IF radio. I have the appropriate carbon-film resistors. I
measured them on my NanoVNA to see what they measure at 432 MHz. Two 200
ohm 1 watt resistors measure 198 ohms on my DVM. The NanoVNA measures 198
otms up to about 500 kHz, and then the resistance starts to climb. At 432
MHz they both measure 225 ohms with a small amount of inductance (12 nH). I
measured a 68 ohm carbon-film resistor with similar results - it measures
67.5 ohms with the DVM and the NanoVNA up to about 500 kHz. At 432 MHz it
measures 86 ohms and a small inductance. I measured a 100 ohm carbon
composition resistor. It measured 102 ohms on the DVM and with the NanoVNA
up to about 1 MHz. The resistance barely changed on the NanoVNA. At 432 MHz
it measured 106 ohms.
73, Zack W9SZ
On Thu, Jul 15, 2021 at 3:30 AM Alan G4ZFQ <alan4alan@...> wrote:
Roland,
Thanks for looking.
It seems whenever meters like the LC-100 are mentioned for use with HF
Ls and Cs someone pops up inferring that the few 100s of KHz they use
will give wrong readings.
I was looking for evidence that such inductors exhibited different
values at different frequencies within their range but you have pointed
out the simple fact that 500KHz is not suitable for measuring mains
power components or VHF components.
Your link gives a good explanation and more detail. I think as you say
these meters are very unlikely to be a problem for checking components
specified for HF use.
73 Alan G4ZFQ
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