NO FCC rf link?

Sounds like an urban legend.

Induction coil? Strange shadow? Absurd.

The radar was running at 50 Hz. ;)

Cheers

Phil Hobbs

On a sunny day (Sun, 14 Feb 2021 08:54:28 -0500) it happened Phil Hobbs wrote in :

Idiot :-)

So at 1 uA the power requirement is 2-3 uW or about -26 dBm, which must be obtained from the antenna.

To clarify (fixed font):

C II RF ----II-----+ II ! --- A LED !

--------------+

The C passes RF which is rectified by the diode/LED but prevents the DC from flowing back to the source (the step up transformer) i.e. a basic RF probe.

The interesting question is, is the LED any good rectifier at VHF/UHF?

Pulse rate.

Spice that and get back to us.

It is much a thing of the past because:

- the radiation culprit is mainly the sweep output stage, and it exists only with vacuum-tube displays,

- in many countries, the analog TV is gone, and the line sweep is a thing of the analog transmission.

That said, there is far too much crud on the HF bands, coming from all other electronic sources, e.g. LED lamps, chopper power supplies etc.

If you want inductive coupling, you would want as large currents to begin with. However, power lines typically operate with quite moderate current levels of a few hundred amperes, regardless if it is a LV, MV or HV line. To minimize electric shock risk, try to avoid HV and possibly also MV lines.

To extract power from the phase conductor, some kind of current transformer should be used. No galvanic connection but you should get the transformer _around_ the phase conductor. The idea used in the example was quire extraordinary :-).

With HV lines available, I would consider capacitive coupling between a single phase conductor and some parallel isolated wire. Assuming 30 pF capacitance between a phase conductor and the pock-up wire. the capacitive reactance at mains frequencies i about 100 Mohm. If the phase conductor is at 230 kV and the wire at ground potential about 2 mA will flow. Letting the wire float to 100 kV, the current will drop to 1 mA, thus 100 W of power would be available.

The problem is of cause isolating your pickup wire and also the capacitance from the pick-up wire to ground forming a capacitive voltage divider. Thus the extracted power would be much less than 100 W. A longer pick-up wire will have a higher stray capacitance and hence more current would be available.

Note the smiley. You really aren't going to get anything much by shooting 10+ GHz waves at an 'induction coil'. An array of rectennas, maybe.

Cheers

Phil Hobbs

Way too much capacitance, not to mention series resistance due to needing a transparent epi layer.

Cheers

Phil Hobbs

Nanowatts maybe, and no "shadow". A tree would absorb more radar than an attic full of diodes.

Besides, radars tend to aim high.

Australia has some enormous fields of insane power HF radars. What's north of Australia to see?

I measured a few. I've seen a few pF and a few hundred, and breakdown voltages over 40.

I have some white Cree diodes that make light with ns rising edges. I would have thought the phosphor would be slow, but it's not.

HF could well be over-the-horizon radar for missile defense, like the DEW line. You can see Russia from Alaska (Tina Fey's front porch), but it's probably easier to keep tabs on China from Oz.

Cheers

Phil Hobbs

Blue LEDs are generally faster than longer wavelengths--there's a factor of (iirc) lambda**-3 in the transition rate due to the higher density of final states at short wavelengths.

I have a white LED box that I use to test photoreceivers--it has somewhat drooly 40-ns edges, but with a blue filter in front of it, it gives nice exponential-looking 10-ns edges. But it depends on the fluors.

Cheers

Phil Hobbs

China.

Google "Jindalee".

Mostly refugee boats and illegal Indonesian fishing boats, I believe.

CH

On a sunny day (Sun, 14 Feb 2021 08:31:14 -0800) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

No idea what frequency you are after, but it will sure work in the MHz range. For much higher frequencies use a BAT diode as rectifier perhaps. I have something like that as RF meter somewhere. If you know the exact frequency use a tuned LC circuit of course.

If you are a big spender then you could add a linear potmeter with switch and button with arrow so you can start looking at high sensitivity, much better than nothing here-nothing there and optimize location end antenna wire. Potmeter scale tells you RF level.

These things are so simple.. takes minutes to build, discussions about it take days what do you have?

Some people have scopes and stick probe in the air? Or a radio even... ;-)

rters. ...

rookie

noise

of them

later it

ham bands?

Thanks for the reply. I was a ham 60 years ago and the TV sets killed a l ot of the fun. Bro still does it big time.

I was also then, and still have a valid highest class licence.