Agreed, but isn¡¯t that R, divided into X at 1 MHz, going to give me Q? It will be terrible. I expected a toroid to offer higher Q than an air core¡
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On Oct 18, 2021, at 4:58 PM, KENT BRITAIN <WA5VJB@...> wrote:
? That 200 Ohms is not the same as a 200 Ohm resistor at any frequency other that 1 MHz.
Again Impedance, not resistance. Kent
On Monday, October 18, 2021, 03:53:18 PM CDT, Andrew Kurtz via groups.io <adkurtz@...> wrote:
Thanks, but I must disagree: the nanoVNA provides a resistance output as well as a reactance, and that is what I was reading to be 200 ohms at 1 MHz...
On Oct 18, 2021, at 4:45 PM, KENT BRITAIN <WA5VJB@...> wrote:
Not really resistance, but impdeance.
Got a good old DC Volt Ohm Meter?
Try that, but you see only 1 or 2 Ohms.
Most of the Digital VOM;s are using pulses that are much like RF.So they are reading as much AC impedance as DC resistance.
Kent
On Monday, October 18, 2021, 03:22:44 PM CDT, Andrew Kurtz via groups.io <adkurtz@...> wrote:
This thread inspires me to ask a question that is not directly about my nanoVNA: I have a toroid from a flea market that is blue, has OD = 0.875¡±, ID = 0.51¡±, and length = 0.3125¡±. I wrapped 6 turns on it, and found (on the VNA) that L is pretty stable around 180 uH. This indicates that Al must be about 5000 mH/turns^2. ( I know NOTHING about toroids¡) but some reference has very few with Al in the range of thousands. Some of them claim high Q, but the VNA indicates a (real) resistance of around 200 ohms at 1 MHz!! This is insanely high; I have air-core inductors for the same service with 60 FEET of wire showing R = 11 ohms at 1 MHz, and this ¡°high-Q¡± toroid, with 11 INCHES of wire, has R = 200 ohms!?! Am I misunderstanding something? So:
- Is there a way to identify my toroid simply because of its size and blue color?
- Is such a high Al, suggesting a very high initial permeability, realistic?
- Why would adding a toroid to less than 1 foot of coil create 200 Ohms resistance?
Thanks!
Andy
On Oct 18, 2021, at 11:37 AM, Tom McKee K4ZAD <tom.m@...> wrote:
On Sat, 16 Oct 2021 Cliff <mailto:kd4gt.tn@...?subject=Re:%20%22Q%22%2C%20Coils%2C%20toroids%2C%20and%20guesswork%3F> wrote about an on line toroid calculator available at:
There is a similar Excel spreadsheet based calculator available for download at:
This link is one of many in my collection of on-line coil calculators available at:
<>
73,
Tom K4ZAD
