Passive crystal radio diode current?
100uA?
10uA?
1uA?
I am asking because I have a very very sensitive analogue current meter and I would love to see the needle to move as the radio is tuned to different stations, to measure their strength.
My meter ia 0-1uA scale but it states also FS=100uA. What does this FS mean?
How mach current you will see depends on the antenna, distance fro teh transmitter and the transmitter power. I have seen a VSWR meter needle lift significantly from the zero stop with the signal receved from a high power medium wave TX about 20km away; it was a good antenna.
FS means Full Scale
You should see something on your 100ua meter if you have a reasoable antenna.
I read somewhere that FS=100uA is the maximum permissible power that the meter can pass without get burnt, regardless if the meter scale is marked 1uA. Is that true?
I have a 100uA meter and a 1uA meter but considering not very good antennas and DX that trying to receive with the radio, wouldn't it be better to use the 1uA meter?
With the 100uA meter I worry thet the needle will barely move, whereas with the 1uA meter I worry that the needle will be over scale. However in the second case, I can add a series resistor, but I just wondering roughly on the amount of current I should expect.
Nonsense, FSD means Full Scale Deflection, in other words the current that makes the needle reach the final marking on the scale. I'm not sure why you have a reference to 1uA but if the scale is 1 to 100 it is probably telling you the resolution rather than maximum.
As for how much current you would measure, bear in mind some field strength meters use 1mA meters and they usually only have a short stick antenna. It depends entirely on how stong the signal you are tuned to is, and that of curse depends on it's initial power and the path losses. If I had to guess 'average' domestic signal strengths, you would probably measure up to around 1uA for an audible but weak signal and 50uA or more for a strong signal.
Brian.
Thanks,
The meter scale is marked 0-1uA incrementing by 0.1 steps (plus the intermediet lines) and at some point at the bottim it writes FS=100uA.
The meter I refer to is listed here http://www.ebay.co.uk/itm/2219568572...%3AMEBIDX%3AIT so you can see an exact picture. I need to know if this is 1uA or 100uA before I buy.
It may be scaled as 0 to 1uA, that will depend on the application it was originally intended for. The FS=100uA is what you should go by. It is a 100uA full scale deflection meter.
That saved me a lot of money, thanks!